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Food Quality and Safety 2017 1 61ndash81doi101093fqsfyx004

Review

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (httpcreativecommonsorglicensesby-nc40) which permits non-commercial re-use distribution and reproduction in any medium provided the original work is properly cited For commercial re-use please contact journalspermissionsoupcom

Review

Recent advances in extraction of antioxidants from plant by-products processing industriesM Selvamuthukumaran and John Shi

Department of Food Science and Post Harvest Technology Institute of Technology Haramaya University PO Box 138 Dire Dawa Ethiopia and Guelph Research and Development Center Agriculture and Agri-Food Canada 93 Stone Road West Guelph Ontario N1G 5C9 Canada

Correspondence to M Selvamuthukumaran Department of Food Science and Post Harvest Technology Institute of Tech-nology Haramaya University PO Box 138 Dire Dawa Ethiopia E-mail msm_foodscienceyahoocoin

Received 21 October 2016 Revised 28 December 2016 Editorial decision 30 December 2016

Abstract

The by-products obtained from plant processing industries are the cheap source of bioactive compounds especially antioxidants Extraction of bioactive compounds can be obtained by using conventional and non-conventional methods Extraction efficiency of any conventional method mainly depends on the choice of solvents The major challenges of conventional extraction are longer extraction time requirement of costly and high purity solvent evaporation of the huge amount of solvent low extraction selectivity and thermal decomposition of thermolabile compounds To overcome these limitations of conventional extraction methods new and promising extraction techniques are introduced These techniques are referred as non-conventional extraction techniques Therefore in this review some of the most promising techniques such as ultrasound-assisted extraction pulsed electric field extraction enzyme-assisted extraction microwave-assisted extraction pressurized liquid extraction supercritical fluid extraction pressurized low-polarity water extraction and molecular distillation were discussed The process systems along with industrial applications for non-conventional method of antioxidants extraction were discussed and the comparative efficacies of different extraction methods were highlighted Replacing conventional technologies by non-conventional ones for the extraction of valuable compounds from plant by-products processing industries has several advantages which includes reduction of the processing time energy consumption and the uses of harmful and expensive solvents and increase in the extraction yields Incorporation and development of hybrid methods should be investigated while considering plant material characteristics and choice of compounds in future Proper choice of standard methods also influences the measurement of extraction efficiency The increasing economic significance of bioactive compounds and commodities rich in these bioactive compounds may lead to find out more sophisticated extraction methods in future

Key words Antioxidants Extraction Non-conventional methods Plant by-products Pulsed electric field extraction Ultrasound-assisted extraction

Introduction

The non-edible portion obtained from plant by-products ranges from 25 to 30 and the inability to recycle such products will significantly contribute to a huge economical loss (Bhalerao et al

1989 Ajila et al 2010) The tissue portion obtained from underuti-lized plant materials was the rich source of several antioxidant com-ponents viz polyphenols carotenoids flavonoids anthocyanins and vitamins (Ayala-Zavala et al 2004) Fruits and vegetable processing

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62 M Selvamuthukumaran and J Shi 2017 Vol 1 No 1

unit delivers several unutilizable waste materials which comprises mainly seeds peel and stones Among them the fruit peel exhib-ited significant antioxidant activity which is around 2- to 27-fold higher than fruit pulp (Someya et al 2002 Guo et al 2003 Goulas and Manganaris 2012) The inexpensive source of antioxidants was reported to be obtained from by-products of several fruits viz star fruit (Shui and Leong 2006) grapes (Lafka et al 2007) citrus fruits (Xu et al 2008) and pomegranate (Singh et al 2002)

The crude extracts obtained from several plant materials were the rich source of phenolic compounds and they have potential applica-tion as preservatives and also used in development of several func-tional foods and nutraceuticals (Marja et al 1999) Therefore the consumption of antioxidant rich foods will scavenge the formation of free radicals and it also helps in preventing the oxidative stress-related diseases (Joshi et al 2012) Fruits and vegetables found to possess several non-digestible components and phytoconstituents in the form of antioxidants which significantly contribute towards the several added health benefits These antioxidants are nowadays widely used as functional ingredients in many processed foods The marketing trend in this field is quiet competitive and therefore the development of new type of quality ingredients is a big challenge for the food processing industries

The term lsquoby-productrsquo means reusuable plant wastes which are having a good market value (Sanchez-Zapata et al 2009) Globally the large amounts of plant wastes were generated from several food processing industries which were estimated to be around 800 000 tyear (Ayala-Zavala et al 2010) The wastes obtained from such industries are highly perishable and they will pose serious environ-mental problems to society (Arvanitoyannis and Varzakas 2008) Table 1 shows the by-products generated from fruits and vegetables processing industries and these by-products comprises mainly of skins seeds stems leaves wastewaters and unusable pulp which are normally discarded after processing (Ajila et al 2007) These by-products amount contributes to more than 40 for plant foods such as artichoke asparagus cactus pear fruit mango orange papaya pineapple red chicory and tiger nuts

The plant by-products are considered to be one of the cheap sources of several antioxidants The extraction of antioxidants from such plant by-products is very much essential for developing

functional food products Higher antioxidant extraction methods are available for use at a commercial level These methods were found to be safe eco-friendly and possess non-carcinogenic effect when compared to synthetic methods The productionrecovery of high-value compounds such as antioxidants is increasingly being considered through the biorefinery concept Bozell and Petersen (2010) Therefore in this review the recent methods in extraction of antioxidants from plant by-products processing industries were discussed and commercial method of antioxidants extraction at a large-scale level and also comparative efficacy of different extraction methods were highlighted The process systems along with industrial applications for non-conventional method of antioxidants were dis-cussed Therefore the food industry can choose the efficient method of extracting functional components from several plant by-products on a large-scale basis and they can deliver several functional food products to the market

Methods of Extraction of Antioxidants

Extraction is a separation process used for separating solutes ie bioactive constituents from solutions using specific solvents by adopting standard procedures (Handa et al 2008) The main pur-pose of this extraction method is to separate the soluble solutes from the plant by-products for performing the efficient extraction process The crude extracts obtained by using these methods con-tain complex mixtures of several plant metabolites viz alkaloids glycosides phenolics terpenoids and flavonoids These extracts are quiet being used as a medicinal agent in the form of tinctures and fluid extracts There are several methods that are available to effi-ciently extract antioxidants from plant by-products of processing industries and these methods are discussed with their commercial applications

Conventional extraction techniquesClassicalconventional extraction techniques are being used at a small scale level to extract bioactive components from several plant materials These techniques are usually based on the extraction effi-ciency of different solvents which are being used for this purpose It

Table 1 Amount of by-products generated from fruit and vegetable processing industry

Fruitvegetable By-products Edible part Reference

Agave 40 (rind and pith) 60 Iniguez-Covarrubias et al (2001)Apple 11 (pulp and seed core) 89 Ayala-Zavala et al (2010)Artichoke Around 60 (outer bracts receptacles and stems) 40 Llorach et al (2002)Asparagus Up to 40ndash50 (spear) 50ndash60 Rodriguez et al (2006)Banana Up to 30 (peel) 70 Schieber et al (2001)Cactus pear cladodes 20 (spines glochids and peel) 80 Bensadon et al (2010)Cactus pear fruit 45 (spines glochids peel and unusable pulp) 65 Bensadon et al (2010)Carrot 30ndash40 (pomace) 60ndash70 Schieber et al (2001)Cyphomandra betacea 15ndash35 (skin pulp and seeds) 65ndash85 Ordonez et al (2010)Guava 10ndash15 (peel and seeds) 85ndash90 Schieber et al (2001)Mandarin 16 (peels) 84 Ayala-Zavala et al (2010)Mango 135 (seeds) 11 (peels) and 179 (unusable pulp) 58 Ayala-Zavala et al (2010)Orange 66 (peel) 44 Li et al (2006)Papaya 65 (seeds) 85 (peels) and 321 (unusable pulp) 53 Ayala-Zavala et al (2010)Passion fruit gt75 (rind and seeds) 25 Schieber et al (2001)Pineapple 91 (core) 135 (peels) 149 (top) and 145 (pulp) 48 Ayala-Zavala et al (2010)Potato 15ndash40 (peel) 60ndash85 Schieber et al (2001)Tomato 3ndash7 (peel and seeds) 93ndash97 Schieber et al (2001)Tiger nuts (lsquoChufarsquo) Up to 60 (solid and liquid wastes) 40 Sanchez-Zapata et al (2009)

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Recent advances in extraction of antioxidants 2017 Vol 1 No 1 63

is a three-process approach which consists of 1 soxhlet extraction 2 maceration and 3 hydrodistillation (HD)

The soxhlet extraction technique has been widely used for extracting several bioactive compounds from various plant materi-als Dry plant material sample needs to be kept in the thimble The thimble is then placed in the distillation flask which contains selec-tive solvent when overflow level of solvent is reached the solution of the thimble-holder is aspirated by a siphon Siphon unloads the solu-tion back into the distillation flask This solution carries extracted solutes into the bulk liquid Solute is remained in the distillation flask and solvent passes back to the solid bed of plant The process runs repeatedly until the extraction is completed

Maceration step was used at homemade level for preparing tonic since from olden days This becomes popular and also one of the cheapest ways to obtain several essential oils and bioactive com-pounds from different plant materials For smaller scale of extrac-tion maceration process generally consists of several steps First the materials are ground ie their size is being reduced in order to increase the surface area for uniform mixing with chosen solvent As a second step in maceration process appropriate solvent ie menstruum is added in a closed vessel Third the liquid is strained off but the marc which is the solid residue of this extraction pro-cess is pressed to recover large amount of occluded solutions The obtained strained and the press out liquid are mixed and separated from impurities by filtration

Occasional shaking in maceration process will facilitate extrac-tion by means of two ways at first it will increase diffusion and second it will remove concentrated solution from the sample sur-face for bringing new solvent to the menstruum for achieving more extraction yield HD which is one of the traditional method used for extracting bioactive compounds and essential oils from several plant materials In this process organic solvents are not involved and it can be performed before dehydration of any plant materials There are three types of HD water distillation water and steam distillation and direct steam distillation (Vankar 2004) In HD first the plant materials are packed in a still compartment sec-ond water is added in sufficient amount and then brought to boil Alternatively direct steam is also injected into the plant sample Both hot water and steam can act as the main influential factors for releasing bioactive compounds from several plant tissues Indirect cooling by water condenses the vapour mixture of water and oil Condensed mixture flows from condenser to a separator where oil and bioactive compounds were separated automatically from the water (Silva et al 2005) HD involves three main physicochemi-cal processes 1 hydrodiffusion 2 hydrolysis and 3 decomposi-tion by heat At higher extraction temperature some of the volatile components will be lost Therefore this drawback limits its use

for extraction of various thermolabile compounds from different plant tissues

The extraction rate of any conventional method mainly depends on the choice of using selective solvents (Cowan 1999) Table 2 shows the examples of various bioactive compounds which are being extracted by using different solvents The solvent polarity is one of the most important factors for the targeted compound and while selecting the solvent the molecular affinity between chosen solvent and solute its environmental safety toxicity and its eco-nomic feasibility needs to be considered to a higher extent for effi-cient extraction of antioxidants

Non-conventional extraction techniquesThe major challenges of conventional extraction are longer extrac-tion time requirement of costly and high purity solvent evapo-ration of the huge amount of solvent low extraction selectivity and thermal decomposition of thermolabile compounds (Luque-de-Castro and Garcia-Ayuso 1998) To overcome these limitations of conventional extraction methods new and promising extrac-tion techniques are introduced These techniques are referred as non-conventional extraction techniques Some of the most prom-ising techniques are ultrasound-assisted extraction (UAE) pulsed electric field (PEF) extraction enzyme-assisted extraction (EAE) microwave-assisted extraction (MAE) pressurized liquid extrac-tion (PLE) supercritical fluid extraction (SFE) pressurized low-polarity water extraction and molecular distillation Some of these techniques are considered as lsquogreen techniquesrsquo as they comply with standards set by Environmental Protection Agency (2015) These include less hazardous chemical synthesis designing safer chemicals safe solvents auxiliaries design for energy efficiency use of renewable feedstock reduce derivatives catalysis design to prevent degradation atom economy and time analysis for pollu-tion prevention and inherently safer chemistry for the prevention of accident

Ultrasound-assisted extractionUltrasound is a special type of sound wave beyond human hear-ing and its frequency ranges from 20 kHz to 100 MHz Like other waves it can pass through a medium by creating compression and expansion Therefore this process produces a phenomenon known as cavitation which further leads in production growth and col-lapse of bubbles A large amount of energy can be produced during the conversion of kinetic energy of motion and thereby it helps in heating the contents of the bubble (Herrera and Luque-de-Castro 2004) According to Suslick and Doktycz (1990) bubbles have temperature about 5000 K pressure of 1000 atmosphere heating

Table 2 Example of some extracted bioactive compounds by different solvents

Water (1000) Ethanol (0654) Methanol (0762) Chloroform (0259) Ether (0117) Acetone (0355)

Anthocyanins Tannins Anthocyanin Terpenoids Alkaloids FlavonoidsTannins Polyphenols Terpenoids Flavonoids TerpenoidsSaponins Flavonol Saponins TanninsTerpenoids Terpenoids Flavones

Alkaloids PolyphenolsAnthocyanin

Values in brackets indicates the relative polarity of each solvents The values for relative polarity are normalized from measurements of solvent shifts of absorp-tion spectra and were extracted from Reichardt (2003)

Source Adapted from Cowan (1999)

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and cooling rate above 1010 Ks Based on this principle UAE has been developed Only liquid and liquid containing solid materials have cavitation effect The intensification of extraction process using ultrasound has been attributed to the cavitation phenomena The effects caused by the ultrasonic waves are compression and expan-sion cycles during the passage through the fluid The expansion can create bubbles or cavities in a liquid This is so when the negative pressure exerted which exceeds the local tensile strength of the liq-uid may varies depending on its nature and purity The process by which vapour bubbles form grow and undergo implosive collapse is known as cavitation The conditions within these imploding bubbles can be dramatic with temperatures of 4500degC and pressures up to 100 MPa which in turn produces very high shear energy waves and turbulence in the cavitation zone The combination of these factors (pressure heat and turbulence) is used to accelerate mass transfer in the extraction process (Patist and Bates 2008)

The extraction mechanism by ultrasound process involves two main types of physical phenomena 1 the diffusion across the cell wall and 2 rinsing the contents of cell after breaking the walls (Mason et al 1996) Moisture content of sample milling degree particle size and solvent are very important factors for obtaining efficient and effective extraction Furthermore temperature pres-sure frequency and time of sonication were the governing factors for the action of ultrasound UAE have also been incorporated along with various classical techniques as they are reported to enhance the efficiency of a conventional system In a solvent extrac-tion unit an ultrasound device is placed in an appropriate position to enhance the extraction efficiency (Vinatoru et al 1998) The advantages of UAE include reduction in extraction time energy and use of solvent Ultrasound energy for extraction also facili-tates more effective mixing faster energy transfer reduced thermal gradients and extraction temperature selective extraction reduced equipment size faster response to process extraction control quick start-up increased production and it eliminates process steps (Chemat et al 2008)

UAE is seemed to be an effective extraction technique for bio-active compound extraction from by-products of fruit and veg-etable processing industries Herrera and Luque-de-Castro (2004) extracted phenolic compounds such as rutin naringin naringenin quercetin ellagic acid and kaempferol from strawberries using 08-s duty cycle for 30 s by developing semi-automatic method based on ultrasounds Anthocyanins and phenolic compounds were extracted from grape peel using UAE and the extraction process was opti-mized with reference to solvent extraction temperature and time (Ghafoor et al 2009 2011) In a study conducted by Cho et al (2006) the impact of UAE on resveratrol recovery from grapes was evaluated With UAE they obtained a significant resveratrol yield (up to 24 and 28 in Campbell and Gerbong grape respectively) and a decrease of the extraction time compared to traditional solvent extraction at 60degC for 30 min Moreover El-Darra et al (2013) also obtained a significant increase (up to 7) in polyphenols (anthocya-nins and tannins content) recovery colour intensity and scavenging activity in the extracts obtained after applying ultrasound treatments (USN) (24 kHz 5ndash15 min 121ndash363 kJkg) during red fermentation of Cabernet Franc grapes

Corrales et al (2008b) studied the effects of UAE combined with thermal treatment (70degC) to recover antioxidant bioactive com-pounds from grape by-products They observed a significant increase in total phenolic compounds of the extracts obtained after apply-ing USN treatments compared to conventional water extraction

Similarly Vilkhu et al (2008) obtained a significant improvement in polyphenols extraction yield (6ndash35) when they applied UAE in red grape marc Recently Da-Porto et al (2013) studied the perfor-mance of conventional solvent extraction (Soxhlet) and ultrasounds on grape seed oil extractions

On the other hand the effects of USN (1010 kJkg) on the recov-ery of proteins and polyphenols from vine shoots was evaluated and a significant increase in the extraction of polyphenols was obtained (Rajha et al 2014) However the energy consumption to reach simi-lar levels of recovered polyphenols was incredibly higher compared to other alternative physical treatments such as high-voltage elec-trical discharges (HVED) (10 kJkg) and PEF (50 kJkg) The UAE method was used to optimize the extraction of phenolic compounds from pumpkins and peaches (Altemimi et al 2016) Lu et al (2015) optimized the UAE conditions using Box-Behnken design and evalu-ated the antioxidant activity of total flavonoids from Cryptotaenia japonica Hassk Their results indicated that UAE is a promising tech-nique for extraction of flavonoids from C japonica Hassk and the flavonoids could be explored as a potential antioxidant agent for use in medicine or functional foods

Process system UAE experiments can be performed with a sonotrode and a glass reaction tank (Hielsher 2013) The double-layered mantle of the reactor which allows the control of extraction temperature with a cooling system by means of water circulation The transducer is connected to the horn with a lsquoboosterrsquo installed in amplification mode and finally the sonotrode which needs to be immersed into the mid-dle of the liquid and samples have to be filled in the tank (Figure 1) Continuous UAE is carried out with an apparatus (Figure 2) which is made up of a circulatory pump and the inlet is placed in a large beaker which contains water and samples (Del-Valle et al 2005)

Industrial applications The interest of UAE lies in the reduced cost due to decrease in time of extraction a more effective and focused use of power a better yield and more concentrated extract at compara-ble SL (solidndashliquid) ratio Conventional maceration process which is quiet time- and energy-consuming process cannot be adopted at commercial level for efficient extraction of antioxidants The extrac-tion process takes a reasonable amount of time (30 min) therefore it is possible for the conversion of the batch system towards a continu-ous system An experimental pilot study was carried out in a con-tinuous piston apparatus for extraction of antioxidants from boldo leaves (Petigny et al 2013) From their lab study they reported that the selected conditions for the ultrasound extraction pilot study were at the optimum conditions of temperature (36degC) and of ultrasound density of power (23 Wcm2) They found that the 30-min time are required to perform an effective and relevant extraction of soluble material which are similar to a conventional maceration process therefore this time of extraction is further optimized for continuous extraction of antioxidants They also found that the yield of solu-ble material from the ultrasound extraction pilot device was equal to batch UAE process at equal time of extraction (217 yield of extraction) Their result showed that the potential use of ultrasound extraction was promising for extraction of antioxidants on an indus-trial scale They concluded that this process can be considered as a sustainable alternative for the industries since it allows simplified handling time reduction quantity of targeted extracts improved and indicating the potential for the use of ultrasound extraction on an industrial scale

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Pulsed electric field extractionThe PEF extraction method was one of the well-known technique for improving the drying extraction and diffusion processes since last decade (Barsotti and Cheftel 1998 Angersbach et al 2000 Vorobiev et al 2005 Vorobiev and Lebovka 2006) The main principle of PEF extraction is to disintegrate the structure of cell membrane for increasing the rate of extraction The electric poten-tial passes through the cell membrane when it is suspended in an electric field and this electric potential separates membrane mol-ecules based on dipole nature ie according to their charge in the cell membrane After exceeding a critical value of approximately 1 V of transmembrane potential there is a repulsion which may occurs between the charge carrying molecules that form pores in weak areas

of the membrane and therefore it causes drastic increase in perme-ability (Bryant and Wolfe 1987) For PEF treatment of plant materi-als a simple circuit with exponential decay pulses is used The plant materials were placed in a treatment chamber which consists of two electrodes Based on treatment chamber design the PEF process can be operated in either continuous or batch mode (Puertolas et al 2010) The effectiveness of PEF treatment depends on the process parameters which includes field strength specific energy input pulse number treatment temperature and properties of the materials to be treated (Heinz et al 2003)

PEF can increase mass transfer during extraction by destroy-ing membrane structure of plant materials for achieving enhanced extraction and thereby decreasing the extraction time PEF has

Figure 1 Batch ultrasonic-assisted extraction (modified from Petigny et al 2013)

Figure 2 Ultrasonic pilot continuous extraction (modified from Petigny et al 2013)

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been applied to improve release of intracellular compounds from plant tissue with the help of increasing the cell membrane perme-ability (Toepfl et al 2006) PEF treatment at a moderate electric field (500 and 1000 Vcm for 10ndash4 to 10ndash2 s) which is found to damage cell membrane of plant tissue with a slight increase in tem-perature (Fincan and Dejmek 2002 Lebovka et al 2002) The PEF can minimize the degradation of heat sensitive compounds (Ade-Omowaye et al 2001) It is also applicable on plant materials as a pre-treatment process prior to conventional extraction method in order to lower the extraction effort (Lopez et al 2009) PEF treat-ment at (1 kVcm with low energy consumption of 7 kJkg) in a solidndashliquid extraction (SLE) process for extraction of betanin from beetroots showed highest degree of extraction compared to freezing and mechanical pressing (Fincan et al 2004) Corrales et al (2008b) extracted bioactive compound such as anthocyanins from grape by-product using various techniques and found better extraction of anthocyanin monoglucosides by PEF The application of a PEF treatment on grape skin before maceration step can reduce the dura-tion of maceration and improve the stability of bioactives (antho-cyanin and polyphenols) during vinification (Lopez et al 2008) The permeabilization of Merlot skin by a PEF treatment resulted in increased extraction of polyphenols and anthocyanins (Delsart et al 2012) For example in the case of grape skins Boussetta et al (2009 2015) have shown that both PEF and HVED treatments had a positive effect on the extraction of polyphenols and total solutes from Chardonnay grape skins The amount of polyphenol extracts was significantly higher immediately after HVED treatment (40 kJkg) (a four times increase as compared to a control extraction) and then reached a maximum After application of PEF treatment (1300 Vcm 200 kJkg) the polyphenol content was also increased twice The initial extraction rates were also different for control extrac-tion and PEF or HVED assisted extraction but the final amounts of polyphenols remains the same after 3 h of extraction process Bouras et al (2016) studied the aqueous solidliquid extraction of the poly-phenols contained in Norway spruce [Picea abies (L) Karst] bark by using PEF treatment The feasibility of PEF treatment was studied through two different PEF protocols with an intensity of E = 20 kVcm These two PEF protocols are applied at different initial humidity of the bark samples (14 and 21) PEF treatments protocols were

compared to untreated samples (simple diffusion without PEF) and to diffusion from sawdust of Norway spruce bark The results of their study showed the positive effect of the PEFs on intracellular compounds extraction The PEF treatment also enhanced extrac-tion of total phenolic content and antioxidant activity They found that the total phenols content was drastically increased to more than eight times as a result of using PEF treatment

Process system The PEF system consists of high current generator treatment unit fluid handling system and controlling equipments The generator of high current supplies electrical pulses of volt-ages shapes and application time by using pulse-forming systems The system consists of power supplier charging resistor capacitor switches inductors and resistors Power generator converts high-voltage (50ndash60 Hz frequency) alternating current (AC) power to the high direct current power (DC) The energy produced by the gen-erator (5ndash80 kV DC) is stored at capacitors and used to generate electric fields

Systems have a switch that is used to discharge high energy through the food materials in treatment chamber Switching systems are the elements that connect storage device (capacitors) and energy load at treatment chamber The switch determines necessary pulse current and application time It acts as a bridge between high-energy suppliers and treatment unit (Mohammed and Ayman 2012 Vallverdu-Queralt et al 2013) It is reported that many different waveforms are being applied in PEF treatment Pulse shapes are commonly being used with either exponentially or square wave Square wave producing systems require a switch with turn off capability or pulse-forming network (Toepfl et al 2007) The PEFs generated by a generator are used in treatment unit or chamber Treatment units are designed to operate either batch or continuous manner The components of PEF treatment and flow chart of process are given in Figure 3 Semi-liquid or liquid food materials are pumped to the treatment chamber at a certain flow rate (5ndash100 mlmin) within co-axial or parallel plate types in chamber (Pizzichemi 2007) The flow of parallel type is being used for batch system while co-axial flow systems are used for continuous types In both systems liquid and semi-liquid materials are being pumped at a certain flow rate and the PEFs are applied at any pulse frequency It is reported that treatment chamber should consist of parallel plate

Figure 3 Components of pulsed electric field treatment and flow chart of process (modified from Gamli 2014)

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electrodes and space insulator The electrodes are separated from the fluid materials by ion conductive membranes that are made up of sulfonated polystyrene and acrylic acid copolymers and electrolyte is being used to simplify electrical conduction between the electrodes and membranes (Dunn and Pearlman 1987)

Industrial applications PEF technology is most widely used in the food processing industries In the 1980s the Krupp (German equipment manufacturer) has performed first attempts to com-mercialize the process but at this time pulsed power switches have not shown sufficient performance and reliability (Sitzmann and Munch 1988 Sitzmann 2006 personal communication) In the 1990s in the USA as well as Europe various food processors equipment manufacturers and universities have been formed to develop PEF applications and equipment (Toepfl et al 2006) In 1995 a continuous system was launched by PurePulse a subsidi-ary of Maxwell Laboratories In 2006 a first commercial instal-lation for fruit juice preservation was achieved in the USA but it was stopped in 2008 due to technical and commercial limita-tions The first commercial operation in Europe was achieved in 2009 with the installation of a 1500 lh juice preservation line In 2010 the first industrial system for processing of vegetables with a maximum capacity of 50 th was started At present such PEF-treated food products were commercially available in countries viz Netherlands Germany and UK where PEF-processing equipment with a capacity of 1500ndash2000 and 5000ndash8000 lh is used (Irving 2012 Mchugh and Toepfl 2016) An industrial system to enhance yield of cloudy apple juice is operated in a German fruit juice com-pany in a 10 th scale (Muller et al 2007) Textural changes was observed in potato sugar beet and carrot after an PEF treatment as a result of facilitation of handling pumping or cutting processes (Lebovka et al 2004 Janositz and Knorr 2010) The process is currently being used with a several industrial installations in order to replace conventional pre-heating of potatoes (60degC 30 min) in French fries production process (Mchugh and Toepfl 2016)

Enzyme-assisted extractionSome phytochemicals in the plant matrices are dispersed in cell cytoplasm and some compounds are retained in the polysaccharide-lignin network by hydrogen bonding or hydrophobic interactions which are not accessible with a solvent in a routine extraction pro-cess Enzymatic pre-treatment has been considered as a novel and an effective way to release bounded compounds and also to increase overall yield (Rosenthal et al 1996) The addition of specific enzymes such as cellulase α-amylase and pectinase during extrac-tion enhances recovery by breaking the cell wall and hydrolyzing the

structural polysaccharides and lipid bodies (Rosenthal et al 1996 Singh et al 1999)

Extraction process There are two approaches for EAE process 1 enzyme-assisted aqueous extraction (EAAE) and 2 enzyme-assisted cold pressing (EACP) (Latif and Anwar 2009) Usually EAAE methods have been developed mainly for the extraction of oils from various seeds (Rosenthal et al 1996 Hanmoungjai et al 2001 Rosenthal et al 2001 Sharma et al 2002) In EACP tech-nique enzymes is used to hydrolyze the seed cell wall because in this system polysaccharide-protein colloid is not available which is obvi-ous in EAAE (Concha et al 2004) Various factors including enzyme composition and concentration particle size of plant materials solid to water ratio and hydrolysis time are recognized as key factors for extraction (Niranjan and Hanmoungjai 2004) Dominguez et al (1995) reported that the moisture content of plant materials is also an important factor for enzymatic hydrolysis

The process of EAE method from the natural products was shown in Figure 4 The breakdown of cell walls is the critical step for the extraction of many bioactive compounds which are existing inside the cell walls EAE is based on the ability of enzymes to hydro-lyze cell wall components and disrupt the structural integrity of the plant cell wall under mild process conditions thereby allowing the efficient extraction and release of the bioactive compounds (Pinelo et al 2006 Gardossi et al 2010) There is a direct proportionality between the rate and the substrate concentration until the enzyme concentration becomes limited (Sowbhagya and Chitra 2010) In this process several parameters need to be considered for efficient extraction process which includes temperature of reaction time of extraction pH of system enzyme concentration and particle size of substrate

Bhattacharjee et al (2006) described EACP as an ideal alternate for extracting bioactive components from oilseed because of its non-toxic and non-inflammable properties The oil extracted by enzyme-assisted methods was found to contain higher amount of free fatty acids and phosphorus contents than traditional hexane extracted oil (Dominguez et al 1995) The EAAE is recognized as eco-friendly technology for extraction of bioactive compounds from oil because it uses water as solvent instead of organic chemicals (Puri et al 2012)

EAAE of phenolic antioxidants from grape pomace during wine production was tested by Meyer et al (1998) who found a cor-relation between yield of total phenols and degree of plant cell wall breakdown by enzyme Landbo and Meyer (2001) showed improved release of phenolic compounds from Ribes nigrum pomace using var-ious enzymes Li et al (2006) extracted total phenolic contents from

Figure 4 The process of enzyme-assisted extraction method from the natural products (modified from Cheng et al 2015)

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five citrus peels (Yen Ben lemon Meyer lemon grapefruit manda-rin and orange) by EAAE using different enzymes and the recovery was highest with celluzyme MX Maier et al (2008) used mixture of pectinolytic and cellulolytic enzyme in the ratio of 21 to extract bioactive compounds (phenolic acids non-anthocyanin flavonoids and anthocyanins) from grape pomace where obtained yields were higher compared with sulfite-assisted extraction Extraction of phe-nolic antioxidant from raspberry solid wastes was increased by application of enzyme in hydro-alcoholic extraction compared with non-enzymatic control (Laroze et al 2010) Gomez-Garcia et al (2012) extracted phenolic compounds from grape waste using dif-ferent types of enzymes viz celluclast pectinex and novoferm in EAAE and found that novoferm had the strongest effect on phenolic release from grape waste

Ranveer et al (2013) conducted the study in order to optimize the extraction process of lycopene by using solvents and also to exam-ine the effect of enzyme treatment on the recovery of lycopene The extraction of lycopene was carried out with four different solvents to know their extraction efficiency Two-step extraction processes was followed for EAE of lycopene In the first step waste samples were treated with enzymes ie cellulase and pectinase where as in second step extraction of lycopene was carried out by using sol-vent Enzyme-assisted solvent extraction of phenolic compounds from watermelon (Citrullus lanatus) rind was optimized (Mushtaq et al 2015) The results obtained indicated that optimized enzyme-assisted solvent extraction enhanced the liberation of antioxidant phenolics up to 3-folds on fresh weight basis as compared to con-ventional solvent extraction with substantial level of total phenolics

Industrial applications The EAE method has several technical limita-tions when it is being commercially adopted (Puri et al 2012) The enzymes used for extraction is quiet expensive for large-scale industrial production process Certain enzymes cannot breakdown the plant cell walls completely Therefore the EAE is not always feasible method to be applied on industrial scale basis because enzymes behaviour was limited by environmental conditions rigidly and the above limitations were needed to be considered in order to make full use of enzymes of potential value in the exploitation and utilization of natural products

Microwave-assisted extractionThe MAE is also considered as a novel method for extracting soluble products into a fluid from a wide range of materials using microwave

energy (Pare et al 1994) Microwaves are electromagnetic fields in the frequency range from 300 MHz to 300 GHz They are made up of two oscillating fields that are perpendicular such as electric field and magnetic field The principle of heating using microwave is based on its direct impacts on polar materials (Letellier and Budzinski 1999) Electromagnetic energy is converted to heat following ionic conduc-tion and dipole rotation mechanisms (Jain 2009) During ionic con-duction mechanism heat is generated because of the resistance of medium to flow ion On the other hand ions keep their direction along field signs which change frequently This frequent change of direc-tions results in collision between molecules and consequently gener-ates heat The larger the dielectric constant of the solvent (Table 3) the more optimal the heating (Kaufmann and Christen 2002) In the case of extraction the advantage of microwave heating is the disrup-tion of weak hydrogen bounds promoted by the dipole rotation of the molecules A higher viscosity of the medium lowers this mechanism by affecting molecular rotation The migration of dissolved ions increases solvent penetration into the matrix and thus facilitates the solvation of the analyte (Kaufmann and Christen 2002) The extraction mecha-nism of MAE is supposed to involve three sequential steps described by Alupului et al (2012) first separation of solutes from active sites of sample matrix under increased temperature and pressure second diffusion of solvent across sample matrix third release of solutes from sample matrix to solvent Several advantages of MAE have been described by Cravottoa et al (2008) such as quicker heating for the extraction of bioactive substances from plant materials reduced ther-mal gradients reduced equipment size and increased extract yield MAE can extract bioactive compounds more rapidly and a better recovery is possible than conventional extraction processes MAE is also recognized as a green technology because it reduces the use of organic solvent (Alupului et al 2012)

Dhobi et al (2009) showed increased extraction efficiency of MAE by extracting a flavolignin silybinin from Silybum mari-anum compared with the conventional extraction techniques such as soxhlet and maceration Asghari et al (2011) extracted some bioactive compounds (E- and Z-guggolsterone cinnamaldehyde and tannin) from various plants under optimum conditions and showed that MAE is a faster and easier method in comparison to conventional extraction processes MAE process from Chinese quince (Chaenomeles sinensis) was optimized for solvent concen-tration extraction time and microwave power using designed experiments to maximize recoveries of flavonoids and phenolics

Table 3 Critical properties of commonly used supercritical fluids

Fluid Molecular weight (gmol) Critical temperature (K) Critical pressure (MPa)

Carbon dioxide 4401 3041 738Water 1802 6473 2212Methane 1604 1904 460Ethane 3007 3053 487Propane 4409 3698 425Ethylene 2805 2824 504Propylene 4208 3649 460Methanol 3204 5126 809Ethanol 4607 5139 614Acetone 5808 5081 470Ammonia 17031 4056 113Chlorotrifluoromethane 10446 302 392Diethyl ether 7412 4677 364n-Pentane 7215 4696 337

Source Adapted from Liong et al (1991)

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and also to enhance electron donating ability of the extracts (Hui et al 2009) Liazid et al (2011) studied the MAE of anthocyanins from grape skins Bittar et al (2013) produced grape juice rich in polyphenols by MAE Yu et al (2014) performed both single-factor and orthogonal experiments to evaluate different MAE processing conditions for polyphenol extraction from grape skin MAE was employed to extract silymarin from milk thistle seeds (Zheng et al 2009) MAE method was applied successfully to extract silymarin from milk thistle seeds Thirugnanasambandham and Sivakumar (2017) optimized the operating parameters in MAE process such as temperature mass of the sample extraction time on the betalain content from dragon fruit peel using response surface methodol-ogy Wild apple fruit dust discarded as by-product from filter tea factory which represents one of the underutilized raw material which found to contain high amount of bioactive compounds Therefore Pavlic et al (in press) utilized the wild apple fruit dust for recovery of polyphenolic antioxidants by application of MAE process Results showed that wild apple fruit dust could be used as good source for recovery of polyphenols and preparation of liquid extracts with increased antioxidant activity

Process system The MAE systems are classified into multi-mode system and focused-mode system (mono-mode) Multi-mode system allows random dispersion of microwave radiation in cavity by a mode stirrer while focused system (mono-mode) allows focused microwave radiation on a restricted zone in cavity Usually the multi-mode system is associated with high pressure (HP) while the mono-mode system is employed under atmospheric operating pressure However mono-mode system can also run at HP In order to avoid confusion in the classification of MAE lsquoClosed Systemrsquo and lsquoOpen Systemrsquo are gener-ally used to refer to the system that operates above atmospheric pres-sure and under atmospheric pressure respectively (Dean and Xiong 2000 Garcia and Castro 2003) The schematic diagrams of closed system and open system are illustrated in Figure 5a and 5b

In a closed MAE system the extractions are carried out in a sealed vessel with different mode of microwave radiations Extraction is normally carried out under uniform microwave heat-ing High working pressure and temperature of the system allow fast and efficient extraction The pressure inside the extraction ves-sel is controlled in such a way that it would not exceed the working pressure of the vessel while the temperature can be regulated above the normal boiling point of the extraction solvent Recent advance-ments in the closed system have led to the development of high-pressure MAE The increase in temperature and pressure accelerates MAE due to the ability of extraction solvent to absorb microwave

energy (Wang et al 2008) Despite the fact that the closed system offers fast and efficient extraction with less solvent consumption but it is susceptible to losses of volatile compounds with limited sample throughput

Open system is developed to counter the shortcomings of closed system such as the safety issues and it is considered more suitable for extracting thermolabile compounds This system has higher sample throughput and more solvent can be added to the system at anytime during the process Basically open system operates at more mild con-ditions Open MAE system is widely used in the extraction of active compounds and it is also used in analytical chemistry This system operates at atmospheric conditions and only part of the vessel is directly exposed to the propagation of microwave radiation (mono-mode) The upper part of the vessel is connected to a reflux unit to condense any vapourized solvent Besides that multi-mode radiation can also be employed in open MAE system with the reflux unit

Industrial applications Filly et al (2014) proposed solvent free microwave extraction as a green method for the extraction of essen-tial oil from aromatic herbs that are extensively used in the food industry This technique is a combination of microwave heating and dry distillation performed at atmospheric pressure without any added solvent or water The isolation and concentration of volatile compounds is performed in a single stage In their work they used solvent free microwave extraction and a conventional technique HD (Clevenger apparatus) as comparative method for the extraction of essential oil from rosemary (Rosmarinus officinalis L) Microwave extraction and separation has been used to increase the concentra-tion of the extract when compared to the conventional method with the same solidliquid ratio which reduces the extraction time and separate at the same time of volatile organic compounds from non-volatile organic compounds of boldo leaves (Petigny et al 2014)

Pressurized liquid extractionPLE was first described by Richter et al (1996) This method is now known by several names pressurized fluid extraction acceler-ated fluid extraction enhanced solvent extraction subcritical water extraction (SWE) and HP solvent extraction (Nieto et al 2010) The concept of PLE is the application of HP to remain solvent liq-uid beyond their normal boiling point HP facilitates the extraction process Automation techniques are the main reason for the greater development of PLE-based techniques along with the decreased extraction time and solvents requirement

PLE technique requires small amounts of solvents because of the combination of HP and temperatures which provides faster

Figure 5 (a) Closed type microwave system and (b) open type microwave system (modified from Mandal et al 2007)

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extraction The higher extraction temperature can promote higher analyte solubility by increasing both solubility and mass transfer rate and also decrease the viscosity and surface tension of solvents thus improving extraction rate (Ibanez et al 2012)

In comparison to the traditional soxhlet extraction PLE was found to dramatically decrease time consumption and solvent use (Richter et al 1996) Therefore for extraction of polar com-pounds PLE which is considered as one of the potential alternative technique to SFE process (Kaufmann and Christen 2002) PLE is also useful for the extraction of organic pollutants from envi-ronmental matrices those are stable at high temperatures (Wang and Weller 2006) PLE has also been used for the extraction of bioactive compounds from marine sponges (Ibanez et al 2012) Applications of PLE technique for obtaining natural products are frequently available in literature (Kaufmann and Christen 2002) Additionally due to small amount of organic solvent use PLE gets broad recognition as a green extraction technique (Ibanez et al 2012)

PLE has been successfully applied to extract bioactive compounds from different plant materials In consideration of yield reproduc-ibility extraction time and solvent consumption PLE has been con-sidered as an alternate to conventional methods due to faster process and lower solvent use Flavonoids extracted from spinach by PLE using a mixture of ethanol and water (7030) solvent at 50ndash150degC were more effective than water solvent at 50ndash130degC (Howard and Pandjaitan 2008) Luthria (2008) showed temperature pressure particle size flush volume static time and solid-to-solvent ratio parameters which are having greater influence on the extraction of phenolic compounds from parsley (Petroselinum crispum) flakes by using PLE method

Some studies have been conducted in order to evaluate the recov-ery of polyphenols from grape pomace and grape skin assisted by HP (200ndash600 MPa 20ndash70degC 30ndash90 min) (Corrales et al 2008a 2008b 2009) All of them obtained a significant increase in the total and individual anthocyanin content after HP processing com-pared to conventional extraction methods On the other hand the potential of HP high temperature (HPHT) to extract phenolic com-pounds from grape by-products (Casazza et al 2010 2012) and particularly resveratrol from grape skins was evaluated obtaining promising results The research group investigated the extraction efficiencies of phenolic compounds from grape seeds and skins using numerous non-conventional versus traditional SLE methods Extraction yields and antioxidant activities were compared between extracts obtained using SLE and non-conventional methods (UAE MAE and HPHT) They found that ethanol was the preferred sol-vent when compared to methanol for both skin and seed extrac-tions They concluded that by using HPHT process high content of total polyphenols o-diphenols and flavonoids in seeds and skins was achieved

Casazza et al (2012) investigated the potential use of HPHT to recover phenolic compounds from grape skins The authors concluded that using HPHT technology resulted in enriched poly-phenol extracts with high antiradical power The grape marc was subjected to phenolic compounds extraction by using HP and tem-perature extraction process Further extracted phenolic compounds were encapsulated at 01 final concentration using a non-emul-sion-based delivery system This encapsulation formulated with natural ingredients (sunflower and palm oils) and a hydrophilic and hydrophobic emulsifier under HP homogenization enhanced the dispersibility in aqueous solutions Antioxidant activities of encap-sulated and non-encapsulated phenolics were evaluated using in

vitro [ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity] and cellular antioxidant assays An interest-ing conclusion of this work was the significant increase in cellular antioxidant activity for the encapsulated grape marc polyphenols when compared to the non-encapsulated molecules revealing the potential of nano-emulsions in the biological membrane delivery systems (Sessa et al 2012)

PLE is an another extraction technique that can enhance extrac-tion rates of bioactive compounds PLE was used to extract anti-oxidants and polyphenols from industrially generated apple pomace A lower temperature range between 75 and 125degC is recommended Using this temperature range a maximum antioxidant activity was determined at 60 ethanol and 102degC By using PLE the antioxi-dant activity was increased 24 times in comparison to traditional SLE and the technique may be a promising alternative to conven-tional techniques for extracting antioxidants Saravana et al (2016) utilized PLE to extract sulfated polysaccharides (fucoidan) from brown seaweed Saccharina japonica They found that the best crude fucoidan yield of 823 was obtained at 140degC temperature with 50 bar pressure Shang et al (2016) optimized the extraction meth-ods for biological compound ie tricin by PLE from black bamboo leaves The optimized extraction methods for biological compound tricin by PLE from black bamboo leaves were obtained at 200degC 50 ethanol 20-min static time and 425-μm particle size achiev-ing high extraction efficiency of 249-mg100-g dry leaves They con-cluded that the high temperature is beneficial for extracting tricin from black bamboo leaves

Process system The PLE set-up is shown in Figure 6 The solvent was pumped into the extraction cell which was placed in an electri-cal heating jacket at a desired temperature until the required pres-sure was obtained Extraction samples were placed in a 657 cm3 extraction cell containing a sintered metal filter at the bottom and upper parts The cell containing the sample was heated filled with extraction solvent and then pressurized The sample was placed in the heating system for 5 min to ensure that the extraction cell would be at the desired temperature (313ndash393 K) during the fill-ing and pressurization procedure After pressurization the sample with pressurized solvent was kept statically at the desired pressure (5ndash10 MPa) for the desired time (3ndash15 min) After PLE the extracts were rapidly cooled to 5degC in ice water using amber flasks to prevent anthocyanin degradation

Industrial applications Ko et al (2016) conducted a pilot-scale SWE plant (8 l scale) for the scale-up and commercialization of the SWE process that extracts antioxidant flavonoids from agricultural by-products such as Citrus unshiu Markovich The effects of oper-ating parameters (extraction temperature extraction time material type solutesolvent ratio and pressure) on the SWE of flavonoids from dried satsuma mandarin peel were studied From the practical aspect the optimum conditions for obtaining flavonoids by pilot-scale SWE were as follows extraction temperature of 130degC extrac-tion time of 15 min and solutesolvent ratio of 134 The yields of flavonoids obtained under laboratory and pilot conditions were sim-ilar 1178 and 1134 mgg satsuma mandarin peel respectively The proportion of flavonoids recovered by SWE in the pilot plant was 963 and large-scale experiments using this method demonstrate its potential industrial applications

SWE is excellent technology to selectively extract flavonoids using temperature-dependent dielectric constant properties of water

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Supercritical fluid extractionThe SFE technique has attracted wide scientific interest and it was successfully used in pharmaceutical polymer and food applications (Zougagh et al 2004) Several industries have been using this tech-nique for many years especially decaffeinated coffee preparation industries (Ndiomu and Simpson 1988) Supercritical state is a dis-tinctive state and can only be attained if a substance is subjected to temperature and pressure beyond its critical point Critical point is defined as the characteristic temperature (Tc) and pressure (Pc) above which distinctive gas and liquid phases do not exist (Inczedy et al 1998) In supercritical state the specific properties of gas andor liquid changes which means supercritical fluid cannot be liquefied by modifying temperature and pressure Supercritical fluid possesses gas-like properties of diffusion viscosity and surface tension and liquid-like density and solvation power These properties make it

suitable for extracting compounds in a short time with higher yields (Sihvonen et al 1999) A basic SFE system consists of the following parts a tank of mobile phase usually CO2 a pump to pressurize the gas co-solvent vessel and pump an oven that contains the extraction vessel a controller to maintain the HP inside the system and a trap-ping vessel Usually different type of meters such as flow meter drywet gas meter could be attached to the system A symmetric diagram of typical SFE instrumentation is given in Figure 7

CO2 is considered as an ideal solvent for SFE The critical temperature of CO2 (31degC) is close to room temperature and the low critical pressure (74 bars) offers the possibility to operate at moderate pressures generally between 100 and 450 bar (Temelli and Guclu-Ustundag 2005) The main drawback of CO2 is its low polarity which makes it ideal for lipid fat and non-polar sub-stance but unsuitable for polar materials The limitation of low

Figure 6 Pressurized liquid extraction set-up (modified from Santos et al 2012)

Figure 7 A symmetric diagram of SFE apparatus (modified from Yi et al 2009)

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polarity of CO2 has been successfully overcome by the use of chemi-cal modifier (Lang and Wai 2001 Ghafoor et al 2010) Usually a small amount of modifier is considered as useful to significantly enhance the polarity of CO2 For example 05 ml of dichlorometh-ane (CH2Cl2) can enhance the extraction which is same for 4-h HD (Hawthorne et al 1994)

The extraction of bioactive compounds from plant materials relies upon several parameter of SFE and most importantly these parameters are tunable (Raverchon and Marco 2006 Raynie 2006 2010) The major variables influencing the extraction efficiency are temperature pressure particle size and moisture content of feed material time of extraction flow rate of CO2 and solvent-to-feed ratio (Temelli and Guclu-Ustundag 2005 Ibanez et al 2012) The advantages of using supercritical fluids for the extraction of bioac-tive compounds can be understood considering following points (Lang and Wai 2001) 1 The supercritical fluid has a higher dif-fusion coefficient and lower viscosity and surface tension than a liquid solvent leading to more penetration to sample matrix and favourable mass transfer Extraction time can be reduced substan-tially by SFE when compared with conventional methods 2 The repeated reflux of supercritical fluid to the sample provides complete extraction 3 The selectivity of supercritical fluid is higher than liq-uid solvent as its solvation power can be tuned by changing either temperature or pressure 4 Separation of solute from solvent in con-ventional extraction process can easily be by-passed by depressuriza-tion of supercritical fluid which will save time 5 SFE is operated at room temperature so an ideal method for thermolabile compound extraction 6 In SFE small amount of sample can be extracted com-pared with solvent extraction methods 7 SFE does not use organic solvent and considered as environment friendly 8 The recycling and reuse of supercritical fluid is possible and thus minimizing waste generation 9 SFE scale can be arranged on specific purpose from few milligram samples in laboratory to tons of sample in industries 10 SFE process provides information regarding extraction process and mechanism which can be manipulated to optimize extraction process

supercritical carbon dioxide (SC-CO2) modified with ethanol (15 wt) gave higher extraction yields of naringin (flavonoid) from citrus paradise than pure SC-CO2 at 95 MPa and 586degC (Giannuzzo et al 2003) Polyphenols and procyanidins were extracted from grape seeds using SFE where methanol was used as modifier and methanol modified CO2 (40) released more than 79 of catechin and epicatechin from grape seed (Khorassani and Taylor 2004) Pascual-Marti et al (2001) evaluated and optimized the SFE conditions [pressure (80ndash110 bar) temperature (40degC) ethanol concentration (5ndash15) and extraction time (5ndash25 min)] to recover resveratrol from grape skin of Vitis vinifera They found that the optimum SFE extraction conditions were obtained at 110 bar 40degC 75 ethanol and extraction time of 15 min Under these conditions the resveratrol content was totally recovered (100) In another study the effect of SC-CO2 extraction (100ndash400 bar35ndash55degC) and the addition of modifier [5 (vv) of ethanol] on the recovery of resveratrol from grape seeds stems skin and pomace of the Palomino Fino grape variety were studied (Casas et al 2010) It was found that the maximum recovery of resveratrol was obtained from skins (491 mg100 g dry sample) when SC-CO2 was used at 400 bar35degC and 5 (vv) of ethanol as co-solvent

Murga et al (2000) evaluated the potential of mixtures of car-bon dioxide and alcohol under supercritical conditions to selectively extract phenolic compounds from grape seeds Louli et al (2004) studied the impact of a combined process of liquid and supercritical

solvent extraction to recover antioxidant compounds from winery by-products The authors studied the effect of solvent type medium composition (skins seeds stems) and crushing pre-treatment on the antioxidant activity of the extract They demonstrated that ethyl acetate used as solvent provides the highest antioxidant activity of extracts Oliveira et al (2013) investigated the antimicrobial activity and the composition profile of the extracts obtained from Merlot and Syrah grape pomace after applying SC-CO2 with co-solvent at pressures up to 300 bar and temperatures of 50 and 60degC Although they found low extraction yields of polyphenols (gallic acid p-OH-benzoic acid vanillic acid and epicatechin) the obtained extracts provided interesting antibacterial (Staphylococcus aureus Bacillus cereus Escherichia coli and Pseudomonas aeruginosa) and antifun-gal (Candida albicans Candida parapsilosis and Candida krusei) activities SFE is successfully and widely used for the extraction of lycopene from ripe tomatoes (Cadoni et al 2000) and tomato pro-cessing wastes (Baysal et al 2000 Kassama et al 2008)

Farias-Campomanes et al (2015) utilized SFE method for extraction of polyphenols from lees of pisco making (an alcoholic beverage made from grapes by-products) SC-CO2 with 10 of eth-anol (ww) was used as extraction solvent Overall extraction curves were determined at 20 and 35 MPa and the experimental data were used to estimate the kinetic parameters Conventional techniques using ethanol as extraction solvent were performed for compara-tive purposes Their results show that the lower yield was obtained when elevated pressures were used They further observed from the kinetic parameters that the mass transfer rate and the amount of the extract dissolved in supercritical phase were found to be higher at 20 MPa than 35 MPa Polyphenols were rapidly extracted with supercritical fluid and more concentrated extracts were obtained at 20 MPa They concluded that the SFE at 20 MPa was the most efficient technique for the extraction of polyphenols from lees of pisco making

Barbosa-Pereira et al (2013) compared two methods of purify-ing the crude extract solid-phase extraction (SPE) and SFE with the aim of improving the quality of the final extract for potential use as safe food additive functional food ingredient or nutraceutical They found that the predominant fractions yielded by SPE were the most active and the fraction eluted with 30 (vv) of methanol displayed the highest antioxidant activity (020 gl) The most active fraction yielded by SFE (EC50 of 023 gl) was obtained under the follow-ing conditions temperature 40degC pressure 140 bar extraction time 30 min ethanol (6) as a modifier and modifier flow 02 mlmin Finally they concluded that SFE is the most suitable procedure for purifying the crude extracts Therefore natural extracts obtained from the residual stream and purified by SFE can be used as natural antioxidants with potential applications in the food cosmetic and pharmaceutical industries

The pentacyclic triterpene αβ-amyrin is a promising bioactive natural product SFE and fractionation were used to obtain penta-cyclic triterpene compounds from dried rosemary leaves (Bensebia et al 2016) Their results showed that the selective recovery of pen-tacyclic triterpene can be optimized by adjusting the pressure and temperature during the extraction process They concluded that the SFE technique as one of the excellent technique for effective extrac-tion of pentacyclic triterpene αβ-amyrin from rosemary leaves

SC-CO2 fluid technology Process system The SC-CO2 fluid extraction process is governed by four key steps extraction expansion separation and solvent

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conditioning The steps are accompanied by four generic primary components extractor (HP vessel) pressure and temperature control system separator and pressure intensifier Raw materials are usually ground and charged into a temperature-controlled extractor form-ing a fixed bed which is usually the case for a batch and single-stage mode (Shi et al 2007a 2007c Kassama et al 2008)

The processes described above are semi-batch continuous processes where the SC-CO2 flows in a continuous mode while the extractable solid feed is charged into the extraction vessel in batches In commer-cial scale processing plants multiple extraction vessels are sequentially used to enhance process performance and output Although the system is interrupted at the end of the extraction period when the process is switched to another vessel prepared for extraction the unloading andor loading of the spent vessels can be carried out while extraction is in progress reducing the downtime and improving the production efficiency A semi-continuous approach on a commercial scale uses a multiple stage extraction processes that involve running the system concurrently by harnessing a series of extraction vessels in tandem In this system the process is not interrupted at the end of extraction period for each vessel because the process is switched to the next pre-pared vessel by control valves for extraction while unloading andor loading the spent vessels Thus SC-CO2 technology is available in the form of single-stage batch that could be upgraded to multistage semi-continuous batch operations coupled with a multi-separation process The need to improve the design into truly continuous modes is growing SC-CO2 fluid extraction could be cost-effective under large-scale production The effects of various parameters of SC-CO2 fluid extractions of tomato skins on the extraction yields and antioxidant activities of lycopene-rich extracts were investigated (Yi et al 2009) The carotenoids in pumpkin were extracted by organic solvents and by SC-CO2 and then they were identified quantified and compared (Kassama et al 2008 Shi et al 2010)

Industrial applications Large-scale SC-CO2 fluid extraction has become a practical process for the extraction of high-value prod-ucts from natural materials The solvating power of SC-CO2 fluids is sensitive to temperature and pressure changes thus the extraction parameters may be optimized to provide the highest possible extrac-tion yields with maximum antioxidant activity for health-promoting components in bioactive extraction production (Kassama et al 2008 Yi et al 2009)

A SC-CO2 fluid extraction process offers the unique advantage of adding value to agricultural waste by extracting bioactives from agricultural by-products which are then used for the fortification of foods and other applications Its drawbacks are the difficulties in extracting polar compounds and compounds from a complex matrix where the phase interaction with the intrinsic properties of the product inhibits its effectiveness These drawbacks can be ame-liorated by using small amounts of food-grade co-solvents (less than 10) to approach the high extraction efficiency (Shi et al 2009) The CO2 density pressure and temperature have been noted to have great impacts on the results of the extraction process When deter-mining the parameters that should be used to maximize yields and solubility of the targeted components many researchers attempted to use conditions that may be applicable in large-scale applications (Shi et al 2007b Kassama et al 2008) For example non-toxic co-solvents and modifiers could be acceptable for food processing therefore a number of researchers have opted to use food-grade co-solvents and modifiers in extraction processes (Shi et al 2009) The nature of the material used as a source of high-value components such as health-promoting components governs the availability of

the compounds for the extraction process The presence of other components such as lipids may impede the process or elevate costs due to an elongated extraction time

Although a high temperature in the extraction process generally increases the solubility of components in supercritical CO2 fluids the conditions under which thermolabile-targeted compounds are nega-tively affected should be considered (Shi et al 2007a 2007c) The intensity and the length of heat processing affect the health-promot-ing properties of bioactives Therefore ideally the extraction time and temperature should be minimized Minimizing such conditions also leads to a more economically viable process (Shi et al 2007b Kassama et al 2008) Excessively high flow rates may reduce the con-tact time between the solute and the solvent and restrict the fluid flow in the sample if it becomes compacted The optimal flow rate appears to vary with the targeted molecule relatively high flow rates having a negative effect on some components Raising the pressure increases extraction yields Sample matrix is an important parameter that influ-ences the solubility and mass transfer process during SC-CO2 extrac-tion Properties such as particle shape and size distribution porosity and pore size distributions surface area and moisture content influ-ence solubility and mass transfer The presence of water (moisture content) in the sample matrix during supercritical extraction also has an effect on the extraction outcome In order to improve the yield and quality of the extracted high-value food components from raw material a pre-treatment of the raw material is an essential process (Yang et al 2008 Zheng et al 2009 Nagendra et al 2010) Cell disruption is the most important pre-treatment and this procedure can be conducted by several processes such as mechanical ultrasonic high electronic field pulse and non-mechanical treatments With improved processing conditions and reduced cost high-value compo-nents extracted from natural materials by SC-CO2 extraction process will become even more economical at high throughput

Pressurized low-polarity water extractionPressurized low-polarity water extraction also known as SWE that is extraction using hot water under pressure has recently become a popular green processing technology and emerges as a promising extraction and fractionation technique for replacing the traditional extraction methods The pressurized low-polarity water extraction is also used in sample preparation to extract organic contaminants from foodstuff for food safety analysis and solidssediments for envi-ronmental monitoring purpose The pressurized low-polarity water extraction process is an environmentally friendly technique that can provide higher extraction yields from solid plant materials (Luque-de-Castro and Jimenez-Carmona 1998) Pressurized low-polarity water extraction is based on the use of water as an extractant in a dynamic mode and under pressure high enough to maintain the liquid state The pressurized low-polarity water extraction process can maintain the water in the liquid (Haar et al 1984 Hawthorne et al 2000) A pressure of 5 MPa would be high enough to prevent the water from vapourizing at temperatures from 100 to 250degC Once pressure is high enough to keep water in a liquid state additional pressure is not necessary as it has limited influence on the solvent characteristics of water Increasing the water temperature from 25 to 250degC causes similar changes in dielectric constant surface tension and viscosity (Kronholm et al 2007 Brunner 2009) Pressurized low-polarity water extraction can easily solubilize organic compounds such as phytochemicals which are normally insoluble in ambient water

Pressurized low-polarity water extraction has the ability to selec-tively extract different classes of compounds depending on the tem-perature used The selectivity of SWE allows for manipulation of the

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composition of the extracts by changing the operating parameters with the more polar ones extracted at lower temperatures and the less polar compounds extracted at higher temperatures (Basile et al 1998 Ammann et al 1999 Clifford et al 1999 Miki et al 1999 Kubatova et al 2001 Soto-Ayala and Luque-de-Castro 2001) Mazza and Pronyk (2015) designed an apparatus for extraction and recovery of antioxidant components from biomass feedstocks with pressurized low-polarity water Their apparatus is configured with two or more reaction columns each separately communicating with sources of pressurized water pressurized heated water and pressur-ized cooling water Components are extracted from the biomass by separately flooding the column with pressurized water heating the column and its contents to the point where the water becomes pres-surized low-polarity water recovering the pressurized low-polarity water comprising the extracted components cooling the column with pressurized low-polarity water and removing the spent biomass material from the column They concluded that the antioxidants can be efficiently extracted by using this system

Process system The instrumentation consists of a water reservoir coupled to a high-pressure pump to introduce the pressurized low-polarity water into the system an oven where the extraction cell is placed and extraction takes place and a restrictor or valve to maintain the pressure (Kronholm et al 2007) Extracts are collected in a vial placed at the end of the extraction system In addition the system can be equipped with a cooling system for rapid cooling of the resultant extract The unique properties of the pressurized low-polarity water extraction are as follows it has a disproportionately high boiling point for its mass with a high dielectric constant and a high-polarity nature As the temperature rises there is a marked and systematic decrease in permittivity an increase in the diffusion rate and a decrease in the viscosity and surface tension of the polar materials

The high degree of association of polar material in the liquid causes its relative permittivity (more commonly called its dielectric constant) to be very high at ca 80 under ambient conditions But as the temperature rises the hydrogen bonding breaks down and the dielectric constant falls The most outstanding feature of this leaching agent is the easy manipulation of its dielectric constant (ε) In fact this parameter can be changed within a wide range just by changing the temperature under moderate pressure Thus at ambi-ent temperature and pressure water has a dielectric constant of ca 80 making it an extremely polar solvent This parameter is drasti-cally lowered by raising the temperature under moderate pressure The subcritical water at 250degC with a pressure over 40 bar has ε = 37 which is similar to ethanol and therefore it easily allows for the leaching of low-polarity compounds and thus between 100 and 200degC this superheated water which behaves like a waterndashmetha-nol mixture so that the efficient extraction of targeted compounds occurs

The solubility of an organic compound with an solvent possess many orders of magnitude which has even got low degree of solu-bility when compared to water at ambient temperature this may be because of two reasons first is the polarity change and second the compound with low solubility at ambient temperature Pressurized low-polarity water will have a high positive enthalpy of solution and thus a large increase in solubility with temperature Because of the greater solubility of some organic compounds in superheated water this medium can be considered for the extraction and other processes to replace conventional organic solvents But some additional reac-tions of the compounds being processed may also occur by hydrolysis oxidation etc

Industrial applications Using pressurized low-polarity water pro-vides a number of advantages over traditional extraction techniques (ie HD organic solvents SLE) These are mainly shorter extraction times higher quality of the extracts (mostly for essential oils) lower costs of the extracting agent and an environmentally compatible tech-nique Since water is perhaps the most environmentally friendly sol-vent available in high purity and at low cost it has been exploited for the extraction of avoparcin in animal tissue (Curren and King 2001) fungicides in agricultural commodities (Pawlowski and Poole 1998) fragrances from cloves (Rovio et al 1999) antioxidative components from sage (Ollanketo et al 2002) anthocyanins and total phenolics from dried red grape skin (Ju and Howard 2003) saponins from cow cockle seed (Guccedillu-Ustundag et al 2007) and other bioactive components from plant materials (Ong and Len 2003) Some addi-tional successful applications of this technique are for the extraction of essential oils from various plant materials (Khajenoori et al 2009 Mortazavi et al 2010) extraction of sweet components from Sirai-tia grosvernorii extraction of lactones from kava roots extraction of antioxidant compounds from microalgae Spirulina platensis (Ibanez et al 1999 2003) extraction of Ginkgo biloba and extraction of bio-phenols from olive leaves (Japon-Lujana and Luque-de-Castro 2006)

The quality of the oil obtained is therefore better than that from steam distillation as it contains more of the oxygenated compounds and lower terpene content The yield is also slightly higher than from steam distillation in spite of the fact that all the terpenes are not extracted This may be because at the higher temperatures and under pressure the plant material is more effectively penetrated However about twice the amount of water is required than for steam distillation Energy costs are much less than for steam distil-lation The energy required to heat a given mass of water from 30 to 150degC under pressure is one-fifth of that needed to boil water at atmospheric pressure from 30degC

Molecular distillationDistillation is a unit operation mainly used for the separation of the mixture constituents by means of partial evaporation It is based on the fact that the vapour is relatively richer in the component with the highest vapour pressure ie the more volatile component Distillation at moderate vacuum is characterized by the use of con-ventional distillation equipment It is lowest pressure limit is on the order of 1 torr ie 1 mm Hg When the distance of transfer is compa-rable with the mean free path of the vapour molecules then the dis-tillation is known as molecular distillation Mean free path is defined as the average distance a molecule will travel in the vapour phase without colliding with another vapour molecule (Eckles et al 1991) This implies that in the molecular distillation system the vapour molecules can reach the condenser without intermolecular collisions Therefore a dynamic equilibrium cannot be established between the vapour and the liquid phase (Eckles et al 1991)

Molecular distillation occurs at very low temperatures and therefore it reduces the problem of thermal decomposition High vacuum also eliminates oxidation that might occur in the presence of air In molecular distillation the rate of evaporation is controlled by the rate at which the molecules escape from the free surface of the liquid and condense on the condenser For this separation pro-cess it is necessary to reveal the behaviour of target components in the evaporation process A molecular distillation procedure was developed to extract the tocotrienols and other minor components from palm fatty acid distillates (PFAD) (Posada et al 2007) The effects of feed flow rate and temperature of distillation on extraction

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of minor components from PFAD were studied in terms of concen-trations distribution coefficients and relative volatilities The minor components were concentrated in the liquid phase at low tempera-tures and in the vapour phase at high temperatures The separation of tocotrienols from FFA approached maximum values only at low temperatures and fell drastically as temperature increased

A study was conducted to determine the antioxidant activity of fractions separated from oregano essential oil by short-path molecu-lar distillation process (Olmedo et al 2014) Two residues (R1 and R2) and two distillates (D1 and D2) fractions were prepared by this process The major components identified were as follows carvacrol terpinen-4-ol and γ-terpinene in R1 and R2 residues γ-terpinene α-terpineol and sabinene in D1 and D2 residues Free radical scaveng-ing activity was also observed in all fractions and results shows that it was highest in R2 residue (772) It was further concluded that the short-path molecular distillation fractions can be successfully used to prepare fractions from oregano essential oil with a higher antioxidant activity Zhang et al (2013) studied the effects of evaporation tempera-ture feeding rate feeding temperature and wiper speed on concentra-tion of ω-3 fatty acids by molecular distillation process Researchers reported the optimum conditions as 1104degC evaporator temperature 787 mlh feeding rate 350 rpm wiper speed 10 MPa operating pres-sure and 80degC feed temperature for concentration of ω-3 fatty acids

Process system In molecular distillation process there are two different types of evaporators were used ie thin-film evaporators (TFE) (Figure 8a) and short-path evaporators (SE) (Figure 8b) In both evaporators feed is agitated with a rotor wiper system and high vacuum is produced by vacuum pumps In TFE operating pressure can be reduced to 1ndash100 mbar (UIC GmbH 2014) and there is no other unit between vacuum and condenser (Pilodist 2014) In SE condenser is placed in the centre of evaporator unit therefore the distance between boiling and condensation surface is extremely reduced and pressure drop is also minimized The operating pressure can be reduced up to 0001 mbar Distilla-tion performed by a SE which is known as molecular distillation and its illustration are given in Figure 8a and 8b (Pilodist 2014 Technoforce 2014) Xu et al (2002) described certain important parameters for molecular distillation process which includes evaporator temperature flow rate vacuum and wiper speed They explained that the flow rate which has got most important desir-able effect over the contact time of the molecules when the mol-ecule is exposed to hot surface during evaporation process Higher flow rates may reduce the residence times of molecules which are being vapourized and wiper speed also affects the film thickness

and viscosity The feed also becomes highly turbulent with inten-sive agitation which leads to high heat-transfer coefficients (Buss-SMS-Canzler GmbH 2014)

Molecular distillation applications Molecular distillation charac-teristics of low pressure and low temperature has great potential for the separation purification and concentration of natural prod-ucts with complex and thermally sensitive molecules The advan-tage of this process is that it can be operated at higher vacuum with shorter time period A commercial production of a typical industrial fractional vacuum distillation plant is shown in Figure 9 The effects of feed flow rate and distillation temperature on the extraction of

Figure 8 Illustration of (a) a thin-film evaporator (TFE) unit and (b) short-path evaporator (SE) unit (modified from Ketenoglu and Tekin 2015)

Figure 9 A typical industrial fractional vacuum distillation plant (modified from Jiang et al 2006)

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minor components are related to the yield purity and rate of evapo-ration in terms of concentrations processes which have gained wide applications for products such as those derived from refined veg-etable oils eg deodorizer distillate of vegetable oils palm oil for obtaining tocotrienols and tocopherols rice oil for oryzanol recov-ery monoglyceride concentration carotenoid recovery from palm oil heavy petroleum characterization and herbicides (Barnicki et al 1996 Shi et al 2007b) A new process of molecular distil-lation was also developed for recovery of tocotrienols and toco-pherols from rapeseed by a combination of acid-catalyzed methyl esterification and crystallization followed by fractional distillation of derived products and for the recovery of orange peel oil and essence products rich in aldehydes esters and other special volatile compounds (Lutisan et al 2002 Jiang et al 2006)

Summary

The comparative effect of conventional solvent extraction UAE MAE and SC-CO2 on the total phenols content total flavonoids individual flavonoids and antioxidant activity of orange peel was studied (Hiri et al 2016) The method that gives the highest total phenol and flavonoid content is MAE followed by UAE conven-tional solvent extraction and SC-CO2 extraction Orange peel extracted by conventional solvent extraction (Table 4) results in the higher radical scavenging capacity compared to the other extracts obtained by MAE UAE and SC-CO2 extraction methods MAE was found to be a better approach than UAE conventional solvent extraction and SC-CO2 extraction methods in terms of phenols flavonoids contents and individual flavonoids MAE showed many advantages such as shorter time higher extraction rate the sav-ing of energy and better products with lower cost compared to SC-CO2 which need high investments on large scale The results demonstrated that MAE can substitute the traditional conventional solvent extraction process which is a time-consuming technique for efficient extraction of orange peel phenolic compounds

Effects of solvent type solvent to solid ratio particle size tem-perature and time on the total phenol content DPPH FRAP and extraction yield in different methods of extraction of antioxidants from pistachio hull were studied (Tabaraki and Ghadiri 2016) MAE method showed the best effect on the extraction of antioxi-dants from pistachio hull The shortest process time was observed for MAE (150-s irradiation time total time of 21 min) with respect to UAE (45 min) and conventional methods (90 min) The energy consumption was 300 W times 25 min and 140 W and 45 min for MAE and UAE respectively Thus MAE method gave better results than UAE and conventional methods with the optimum operating condi-tions such as time and energy consumption Other methods such as

PLE and SFE were also being used in the extraction of plant mate-rials These methods are less popular due to high cost despite the efficiency of the methods (Azwanida 2015)

The ever-growing demand to extract plant bioactive compounds encourages continuous search for convenient extraction methods Replacing conventional technologies by non-conventional ones for the extraction of valuable compounds from plant by-products pro-cessing industries represents numerous advantages including the reduction of the consumed energy non-toxic organic solvents and the increase of the extraction yields in full correspondence with green extraction concept Furthermore some non-conventional technologies are able to extract selectively the intracellular mole-cules without fragmenting the treated tissue which is highly sought to reduce the subsequent purification steps Incorporation and development of hybrid methods should also be investigated con-sidering plant material characteristics and choice of compounds The increasing economic significance of bioactive compounds and commodities rich in these bioactive compounds may lead to find out more sophisticated extraction methods in future

Conflict of interest statement None declared

ReferencesAde-Omowaye B I O Angersbach A Taiwo K A Knorr D (2001) Use

of pulsed electric field pre-treatment to improve dehydration character-istics of plant based foods Trends in Food Science amp Technology 12 285ndash295

Ajila C M Aalami M Leelavathi K Prasada-Rao U J S (2010) Mango peel powder a potential source of antioxidant and dietary fibre in maca-roni preparations Innovative Food Science and Emerging Technologies 11 219ndash224

Ajila C M Bhat S G Prasada-Rao U J S (2007) Valuable components of raw and ripe peels from two Indian mango varieties Food Chemistry 102 1006ndash1011

Altemimi A Watson D G Choudhary R Dasari M R Lightfoot D A (2016) Ultrasound assisted extraction of phenolic compounds from peaches and pumpkins PLoS One 11 1ndash20

Alupului A Calinescu I Lavric V (2012) Microwave extraction of active principles from medicinal plants UPB Science Bulletin Series B 74 129ndash142

Ammann A Hinz D C Addleman R S Wai C M Wenclawiak B W (1999) Superheated water extraction steam distillation and SFE of pepper mint oil Freseniusrsquo Journal of Analytical Chemistry 364 650ndash653

Angersbach A Heinz V Knorr D (2000) Effects of pulsed electric fields on cell membranes in real food systems Innovative Food Science and Emerg-ing Technologies 2 135ndash149

Arvanitoyannis I S Varzakas T H (2008) Vegetable waste treatment com-parison and critical presentation of methodologies Critical Reviews in Food Science and Nutrition 48 205ndash247

Table 4 Extraction conditions of conventional solvent extraction UAE MAE and SC-CO2 methods MAE microwave-assisted extraction SC-CO2 supercritical carbon dioxide extraction UAE ultrasound-assisted extraction

Extraction method Conditions of extraction Characteristics

Conventional solvent extraction

Ethanol (80) mv 5 g 50 ml 30 min 35degC me-chanical stirring at darkness 3 successive extractions

mdash

UAE Ethanol (80) mv 5 g 50 ml 30 min 35degC magnet-ic stirring at darkness 3 successive extractions 125 W

Ultrasound sonicator (VibraCell 75115 Bioblock-Fisher Illkirch France)

MAE Ethanol (80) mv 5 g 50 ml 10 s 35degC 170 W 3 successive extractions

Microwave oven (WAVEDOM LG France)

SC-CO2 Ethanol (80) mv 5 g 50 ml 30 min 35degC 22 MPa 3 successive extractions

Pilot-scale extractor (ENSIC LRGP Nancy France)

Source Hiri et al (2016)

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Asghari J Ondruschka B Mazaheritehrani M (2011) Extraction of bioac-tive chemical compounds from the medicinal Asian plants by microwave irradiation Journal of Medicinal Plants Research 5 495ndash506

Ayala-Zavala J F Rosas-Dominguez C Vega-Vega V Gonzalez-Aguilar G A (2010) Antioxidant enrichment and antimicrobial protection of fresh-cut fruits using their own byproducts looking for integral exploitation Journal of Food Science 75 R175ndashR181

Ayala-Zavala J F Wang S Y Wang C Y Gonzalez-Aguilar G A (2004) Effect of temperature on antioxidant capacity and aroma compounds in strawberry fruit Lebensmittel Wissenschaft und Technologie 37 687ndash695

Azwanida N N (2015) A review on the extraction methods use in medicinal plants principle strength and limitation Medicinal amp Aromatic Plants 4 1ndash6

Barbosa-Pereira L Pocheville A Angulo I Paseiro-Losada P Cruz J M (2013) Fractionation and purification of bioactive compounds obtained from a brewery waste stream BioMed Research International 2013 408491

Barnicki S D Sumner C E Williams H C (1996) Process for the Produc-tion of Tocopherol Concentrates US Patent No 5512691 1ndash38

Barsotti L Cheftel J C (1998) Treatment of food by electric fields pulses Sciences des Aliments 18 584ndash601

Basile A Jimenez-Carmona M M Clifford A A (1998) Extraction of rose-mary by superheated water Journal of Agricultural and Food Chemistry 46 5204ndash5209

Baysal T Ersus S Starmans J D A (2000) Supercritical CO2 extraction of β-carotene and lycopene from tomato paste waste Journal of Agricultural and Food Chemistry 48 5507ndash5511

Bensadon S Hervert-Hernandez D Sayago-Ayerdi S Goni I (2010) By-products of Opuntia ficus-indica as a source of antioxidant dietary fiber Plant Foods for Human Nutrition 65 210ndash216

Bensebia O Bensebia B Allia K H Barth D (2016) Supercritical CO2 extraction of triterpenes from rosemary leaves kinetics and modeling Separation Science and Technology 51 2174ndash2182

Bhalerao S D Mulmuley G V Ananthakrishna S M Potty V H (1989) Waste and waste water management in food industry fruit and vegetable processing Indian Food Packer 43 5ndash11

Bhattacharjee P Singhal R S Tiwari S R (2006) Supercritical carbon diox-ide extraction of cottonseed oil Journal of Food Engineering 79 892ndash989

Bittar S A Perino-Issartier S Dangles O Chemat F (2013) An innova-tive grape juice enriched in polyphenols by microwave-assisted extraction Food Chemistry 141 3268ndash3272

Bouras M Grimi N Bals O Vorobiev E (2016) Impact of pulsed elec-tric fields on polyphenols extraction from Norway spruce bark Industrial Crops and Products 80 50ndash58

Boussetta N Grimi N Vorobiev E (2015) Pulsed electrical technolo-gies assisted polyphenols extraction from agricultural plants and biore-sources a review International Journal of Food Processing Technology 2 1ndash10

Boussetta N Lebovka N Vorobiev E Adenier H Bedel-Cloutour C Lanoiselle J L (2009) Electrically assisted extraction of soluble matter from Chardonnay grape skins for polyphenol recovery Journal of Agricul-tural and Food Chemistry 57 1491ndash1497

Bozell J J Petersen G R (2010) Technology development for the production of biobased products from biorefinery carbohydrates ndash the US Department of Energyrsquos ldquoTop 10rdquo revisited Green Chemistry 12 539ndash554

Brunner G (2009) Near critical and supercritical water Part I Hydro-lytic and hydrothermal processes Journal of Supercritical Fluids 47 373ndash381

Bryant G Wolfe J (1987) Electromechanical stress produced in the plasma membranes of suspended cells by applied electrical fields Journal of Mem-brane Biology 96 129ndash139

Buss-SMS-Canzler GmbH (2014) General Description of Thin Film Distil-lation httpwwwsms-vtcomentechnologiesthin-film-evaporatorthin-film-distillationhtml

Cadoni E Giorgi M R Medda E Poma G (2000) Supercritical CO2 extraction of lycopene and β-carotene from ripe tomatoes Dyes and Pig-ments 44 27ndash32

Casas L Mantell C Rodriacuteguez M De-la-Ossa E J M Roldan A De-Ory I Caro I Blandino A (2010) Extraction of resveratrol from the pomace of Palomino fino grapes by supercritical carbon dioxide Journal of Food Engineering 96 304ndash308

Casazza A A Aliakbarian B Mantegna S Cravotto G Perego P (2010) Extraction of phenolics from Vitis vinifera wastes using non-conventional techniques Journal of Food Engineering 100 50ndash55

Casazza A A Aliakbarian B Sannita E Perego P (2012) High-pressure high temperature extraction of phenolic compounds from grape skins International Journal of Food Science amp Technology 47 399ndash405

Chemat F Tomao V Virot M (2008) Handbook of Food Analysis Instru-ments Ultrasound-Assisted Extraction in Food Analysis Boca Raton FL CRC Press pp 85ndash94

Cheng X Bi L Zhao Z Chen Y (2015) Advances in enzyme assisted extraction of natural products 3rd International Conference on Mate-rial Mechanical and Manufacturing Engineering (IC3ME 2015) Atlantis Press Guangzhou China pp 371ndash375

Cho Y J Hong J Y Chun H S Lee S K Min H Y (2006) Ultrasonica-tion-assisted extraction of resveratrol from grapes Journal of Food Engi-neering 77 725ndash730

Clifford A A Basile A Salim H R A-S (1999) A comparison of the extraction of clove buds with supercritical carbon dioxide and super-heated water Freseniusrsquo Journal of Analytical Chemistry 364 635ndash637

Concha J Soto C Chamy R Zuniga M E (2004) Enzymatic pretreat-ment on rose-hip oil extraction hydrolysis and pressing conditions Jour-nal of the American Oil Chemistsrsquo Society 81 549ndash552

Corrales M Butza P Tauschera B (2008a) Anthocyanin condensation reactions under high hydrostatic pressure Food Chemistry 110 627ndash635

Corrales M Garcia A F Butz P Tauscher B (2009) Extraction of antho-cyanins from grape skins assisted by high hydrostatic pressure Journal of Food Engineering 90 415ndash421

Corrales M Toepflb S Butza P Knorrc D Tauschera B (2008b) Extrac-tion of anthocyanins from grape by-products assisted by ultrasonics high hydrostatic pressure or pulsed electric fields a comparison Innovative Food Science and Emerging Technologies 9 85ndash91

Cowan M M (1999) Plant products as antimicrobial agents Clinical Micro-biology Reviews 12 564ndash582

Cravottoa G Boffaa L Mantegnaa S Peregob P Avogadrob M Cintasc P (2008) Improved extraction of vegetable oils under high-intensity ultrasound andor microwaves Ultrasonics Sonochemistry 15 898ndash902

Curren M S S King J W (2001) Ethanol-modified subcritical water extrac-tion combined with solid-phase micro extraction for determining atrazine in beef kidney Journal of Agricultural and Food Chemistry 49 2175ndash2180

Da-Porto C Porretto E Decorti D (2013) Comparison of ultrasound-assisted extraction with conventional extraction methods of oil and poly-phenols from grape (Vitis vinifera L) seeds Ultrasonics Sonochemistry 20 1076ndash1080

Dean J R Xiong G (2000) Extraction of organic pollutants from environ-mental matrices selection of extraction technique Trends in Analytical Chemistry 19 553ndash564

Delsart C Ghidossi R Poupot C Cholet C Grimi N Vorobiev E Mili-sic V Peuchot M (2012) Enhanced extraction of phenolic compounds from Merlot grapes by pulsed electric field treatment American Journal of Enology and Viticulture 63 205ndash211

Del-Valle J M Rogalinski T Zetzl C Brunner G (2005) Extraction of boldo (Peumus boldus M) leaves with supercritical CO2 and hot pressur-ized water Food Research International 38 203ndash213

Dhobi M Mandal V Hemalatha S (2009) Optimization of microwave assisted extraction of bioactive flavolignanndashsilybinin Journal of Chemical Metrology 3 13ndash23

Dominguez H Ntiiiez M J Lema J M (1995) Enzyme-assisted hexane extraction of soybean oil Food Chemistry 54 223ndash231

Dunn J E Pearlman J S (1987) Methods and Apparatus for Extending Shelf Life of Fluid Food Products US Patent No 4695472

Eckles A Benz P Fine S (1991) When to use high-vacuum distillation Chemical Engineering 98 201ndash203

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El-Darra N Grimi-Eugene N Nicolas V Maroun L R (2013) Extraction of polyphenols from red grape pomace assisted by pulsed ohmic heating Food and Bioprocess Technology 6 1281ndash1289

Environmental Protection Agency (2015) Green Chemistry httpswwwepagovgreenchemistry

Farias-Campomanes A M Rostagno M A Coaquira-Quispe J J Meireles M A A (2015) Polyphenols from lees overall extraction curve kinetic data and composition of the extracts Bioresources and Bioprocessing 2 45

Filly A Fernandez X Minuti M Visinoni F Cravotto G Chemat F (2014) Solvent free microwave extraction of essential oil from aromatic herbs from laboratory to pilot and industrial scale Food Chemistry 150 193ndash198

Fincan M Dejmek P (2002) In situ visualization of the effect of a pulsed electric field on plant tissue Journal of Food Engineering 55 223ndash230

Fincan M De-Vito F Dejmek P (2004) Pulsed electric field treatment for solidndashliquid extraction of red beetroot pigment Journal of Food Engineer-ing 64 381ndash388

Gamli F (2014) A review of application of pulsed electric field in the produc-tion of liquidsemi-liquid food materials Advance Research in Agriculture and Veterinary Science 1 54ndash61

Garcia J L Castro M D (2003) Where is microwave-based analytical equipment for solid sample pre-treatment going Trends in Analytical Chemistry 22 90ndash98

Gardossi L Poulsen P B Ballesteros A Hult K Svedas V K Vasic-Racki D Carrea G Magnusson A Schmid A Wohlgemuth R Halling P J (2010) Guidelines for reporting of biocatalytic reactions Trends in Bio-technology 28 171ndash180

Ghafoor K Choi Y H Jeon J Y Jo I H (2009) Optimization of ultra-sound-assisted extraction of phenolic compounds antioxidants and anthocyanins from grape (Vitis vinifera) seeds Journal of Agricultural and Food Chemistry 57 4988ndash4994

Ghafoor K Hui T Choi Y H (2011) Optimization of ultrasound-assisted extraction of total anthocyanins from grape peel Journal of Food Bio-chemistry 35 735ndash746

Ghafoor K Park J Choi Y H (2010) Optimization of supercritical carbon dioxide extraction of bioactive compounds from grape peel (Vitis labrusca B) by using response surface methodology Innovative Food Science and Emerging Technologies 11 485ndash490

Giannuzzo A N Boggetti H J Nazareno M A Mishima H T (2003) Supercritical fluid extraction of naringin from the peel of citrus paradise Phytochemical Analysis 14 221ndash223

Gomez-Garcia R Martinez-Avila G C G Aguilar C N (2012) Enzyme-assisted extraction of antioxidative phenolics from grape (Vitis vinifera L) residues 3 Biotech 2 297ndash300

Goulas V Manganaris G A (2012) Exploring the phytochemical content and the antioxidant potential of citrus fruits grown in Cyprus Food Chemistry 131 39ndash47

Guccedillu-Ustundag O Mazza G Balsevich J (2007) Pressurized low polar-ity water extraction of saponins from cow cockle seed Journal of Food Engineering 80 619ndash630

Guo C Yang J Wei J Li Y Xu J Jaing Y (2003) Antioxidant activities of peel pulp and seed fractions of common fruits as determined by FRAP assay Nutrition Research 23 1719ndash1726

Haar L Gallagher J S Kell G S (1984) National Bureau of StandardsNational Research Council Steam Tables Hemisphere Publishing Bristol PA

Handa S S Khanuja S P S Longo G Rakesh D D (2008) Extraction Technologies for Medicinal and Aromatic Plants United Nations Indus-trial Development Organization and the International Centre for Science and High Technology Trieste Italy No 66

Hanmoungjai P Pyle D L Niranjan K (2001) Enzymatic process for extracting oil and protein from rice bran Journal of the American Oil Chemistsrsquo Society 78 817ndash821

Hawthorne S B Grabanski C B Martin E Miller D J (2000) Com-parisons of soxhlet extraction pressurized liquid extraction supercritical fluid extraction and subcritical water extraction for environmental solids

recovery selectivity and effects on sample matrix Journal of Chromatog-raphy A 892 421ndash433

Hawthorne S B Yang Y Miller D J (1994) Extraction of organic pollut-ants from environmental solids with sub- and supercritical water Analyti-cal Chemistry 66 2912ndash2920

Heinz V Toepfl S Knorr D (2003) Impact of temperature on lethality and energy efficiency of apple juice pasteurization by pulsed electric fields treat-ment Innovative Food Science and Emerging Technologies 4 167ndash175

Herrera M C Luque-de-Castro M D (2004) Ultrasound-assisted extrac-tion for the analysis of phenolic compounds in strawberries Analytical and Bioanalytical Chemistry 379 1106ndash1112

Hielsher (2013) Ultrasonically assisted catalytic extraction Heilscher Ultra-sonics gmbh Teltow Germany httpwwwhielschercom

Hiri N Ioannou I Paris C Ghoul M Mihoubi B N (2016) Comparison of the efficiency of different extraction methods on antioxidants of Mal-tease orange peel Journal of Food Science 3 1ndash13

Howard L Pandjaitan N (2008) Pressurized liquid extraction of flavonoids from spinach Journal of Food Science 73 C151ndashC157

Hui T Ghafoor K Choi Y H (2009) Optimization of microwave-assisted extraction of active components from Chinese quince using response sur-face methodology Journal of the Korean Society for Applied Biological Chemistry 52 694ndash701

Ibanez E Herrero M Mendiola J A Castro-Puyana M (2012) Extraction and characterization of bioactive compounds with health benefits from marine resources macro and micro algae cyanobacteria and inverte-brates In Hayes M (ed) Marine Bioactive Compounds Sources Char-acterization and Applications Springer New York NY pp 55ndash98

Ibanez E Kubatova A Senorans F J Cavero S Reglero G Hawthorne S B (2003) Subcritical water extraction of antioxidant compounds from rosemary plants Journal of Agricultural and Food Chemistry 51 375ndash382

Ibanez E Oca A De-Murga G Lopez-Sebastian S Tabera J Reglero G (1999) Supercrtical fluid extraction and fractionation of different pre-processed rosemary plants Journal of Agricultural and Food Chemistry 47 1400ndash1404

Inczedy J Lengyel T Ure A M (1998) Supercritical Fluid Chromatogra-phy and Extraction Compendium of Analytical Nomenclature (Definitive Rules 1997) Blackwell Science Oxford UK

Iniguez-Covarrubias G Lange S E Rowell R M (2001) Utilization of byproducts from the tequila industry part 1 agave bagasse as a raw mate-rial for animal feeding and fiber board production Bioresource Technol-ogy 77 25ndash32

Irving D (2012) We are already up-scaling VMT Food Technology 16 11ndash13

Jain T (2009) Microwave assisted extraction for phytoconstituents ndash an over-view Asian Journal of Research in Chemistry 2 19ndash25

Janositz A Knorr D (2010) Microscopic visualization of pulsed electric field induced changes on plant cellular level Innovative Food Science and Emerging Technologies 11 592ndash597

Japon-Lujana R Luque-de-Castro M D (2006) Superheated liquid extrac-tion of oleuropein and related biophenols from olive leaves Journal of Chromatography A 1136 185ndash191

Jiang S T Shao P Pan L J Zhao Y Y (2006) Molecular distillation for recovering tocopherol and fatty acid methyl esters from rapeseed oil deo-dorizer distillate Biosystems Engineering 93 383ndash391

Joshi V K Kumar A Kumar V (2012) Antimicrobial antioxidant and phy-tochemicals from fruit and vegetable wastes a review International Jour-nal of Food and Fermentation Technology 2 123ndash136

Ju Z Y Howard L R (2003) Effects of solvent and temperature on pressurized liquid extraction of anthocyanins and total phenolics from dried red grape skin Journal of Agricultural and Food Chemistry 51 5207ndash5213

Kassama L S Shi J Mittal G S (2008) Optimization of supercritical fluid extraction of lycopene from tomato skin with central composite rotatable design model Separation and Purification Technology 60 278ndash284

Kaufmann B Christen P (2002) Recent extraction techniques for natural products microwave-assisted extraction and pressurized solvent extrac-tion Phytochemical Analysis 13 105ndash113

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Ketenoglu O Tekin A (2015) Applications of molecular distillation tech-nique in food products Italian Journal of Food Science 27 277ndash281

Khajenoori M Haghighi-Asl A Hormozi F (2009) Proposed models for subcritical water extraction of essential oils Chinese Journal of Chemical Engineering 17 359ndash365

Khorassani M A Taylor L T (2004) Sequential fractionation of grape seeds into oils polyphenols and procyanidins via a single system employing CO2-based fluids Journal of Agricultural and Food Chemistry 52 2440ndash2444

Ko M J Kwon H L Chung M S (2016) Pilot-scale subcritical water extraction of flavonoids from satsuma mandarin (Citrus unshiu Marko-vich) peel Innovative Food Science and Emerging Technologies 38 175ndash181

Kronholm J Hartonen K Riekkola M L (2007) Analytical extractions with water at elevated temperatures and pressures Trends in Analytical Chemistry 26 396ndash412

Kubatova A Lagadec A J M Miller D J Hawthorne S B (2001) Selec-tive extraction of oxygenates from savoury and peppermint using subcriti-cal water Flavour and Fragrance Journal 16 64ndash73

Lafka T I Sinanoglou V Lazos E S (2007) On the extraction and antioxi-dant activity of phenolic compounds from winery wastes Food Chemistry 104 1206ndash1214

Landbo A K Meyer A S (2001) Enzyme-assisted extraction of antioxida-tive phenols from black currant juice press residues (Ribes nigrum) Jour-nal of Agricultural and Food Chemistry 49 3169ndash3177

Lang Q Wai C M (2001) Supercritical fluid extraction in herbal and natu-ral product studiesmdasha practical review Talanta 53 771ndash782

Laroze L Soto C Zuniga M E (2010) Phenolic antioxidants extraction from raspberry wastes assisted by-enzymes Electronic Journal of Biotech-nology 13 1ndash11 doi 102225vol13-issue6-fulltext-12

Latif S Anwar F (2009) Physicochemical studies of hemp (Cannabis sativa) seed oil using enzyme-assisted cold-pressing European Journal of Lipid Science and Technology 111 1042ndash1048

Lebovka N I Bazhal M I Vorobiev E (2002) Estimation of characteristic damage time of food materials in pulsed-electric fields Journal of Food Engineering 54 337ndash346

Lebovka N I Praporscic I Vorobiev E (2004) Effect of moderate ther-mal and pulsed electric field treatments on textural properties of carrots potatoes and apples Innovative Food Science amp Emerging Technologies 5 9ndash16

Letellier M Budzinski H (1999) Microwave assisted extraction of organic compounds Analusis 27 259ndash270

Li B B Smith B Hossain M M (2006) Separation and purification in the food industry extraction of phenolics from citrus peels II Enzyme-assisted extraction method Separation and Purification Technology 48 189ndash196

Liazid A Guerrero R F Cantos E Palma M Barroso C G (2011) Microwave assisted extraction of anthocyanins from grape skins Food Chemistry 124 1238ndash1243

Liong K K Wells P A Foster N R (1991) Diffusion in supercritical fluids The Journal of Supercritical Fluids 4 91ndash108

Llorach R Espin J C Tomas-Barberan F A Ferreres F (2002) Artichoke (Cynara scolymus L) byproducts as a potential source of health-promot-ing antioxidant phenolics Journal of Agricultural and Food Chemistry 50 3458ndash3464

Lopez N Puertolas E Condon S Alvarez I Raso J (2008) Effects of pulsed electric fields on the extraction of phenolic compounds during the fermentation of must of Tempranillo grapes Innovative Food Science and Emerging Technologies 9 477ndash482

Lopez N Puertolas E Condon S Raso J Alvarez I (2009) Enhancement of the extraction of betanine from red beetroot by pulsed electric fields Journal of Food Engineering 90 60ndash66

Louli V Ragoussis N Magoulas K (2004) Recovery of phenolic anti-oxidants from wine industry by-products Bioresource Technology 92 201ndash208

Lu J Xu Y Yang M Fu X Luo F Li Z (2015) Optimization of ultrasound-assisted extraction of flavonoids from Cryptotaenia japonica

Hassk evaluation of antioxidant activity Journal of Agricultural Science 7 138ndash146

Luque-de-Castro M D Garcia-Ayuso L E (1998) Soxhlet extraction of solid materials an outdated technique with a promising innovative future Analytica Chimica Acta 369 1ndash10

Luque-de-Castro M D Jimenez-Carmona M M (1998) Potential of water for continuous automated sample leaching Trends in Analytical Chemis-try 17 441ndash447

Luthria D L (2008) Influence of experimental conditions on the extraction of phenolic compounds from parsley (Petroselinum crispum) flakes using a pressurized liquid extractor Food Chemistry 107 745ndash752

Lutisan J Cvengros J Micov M (2002) Heat and mass transfer in the evaporating film of a molecular evaporator Chemical Engineering Journal 85 225ndash234

Maier T Goppert A Kammerer D R Schieber A Carle R (2008) Opti-mization of a process for enzyme-assisted pigment extraction from grape (Vitis vinifera L) pomace European Food Research and Technology 227 267ndash275

Mandal V Mohan Y Hemalatha S (2007) Microwave assisted extraction ndash an innovative and promising extraction tool for medicinal plant research Pharmacognosy Reviews 1 7ndash18

Marja P K Anu I H Heikki J V Jussi-Pekka R Kalevi P Tytti S K Marina H (1999) Antioxidant activity of plant extracts containing phenolic compounds Journal of Agricultural and Food Chemistry 47 3954ndash3962

Mason T J Paniwnyk L Lorimer J P (1996) The uses of ultrasound in food technology Ultrasonics Sonochemistry 3 253ndash260

Mazza G Pronyk C (2015) Pressurized Low Polarity Water Extraction Apparatus and Methods of Use Patent No US 9084948 B2

Mchugh T Toepfl S (2016) Pulsed electric field processing for fruits and vegetables Food Technology 70 73ndash75

Meyer A S Jepsen S M Sorensen N S (1998) Enzymatic release of anti-oxidants for human low-density lipoprotein from grape pomace Journal of Agricultural and Food Chemistry 46 2439ndash2446

Miki W Nakahara K Fujii T Nagami K Arai K (1999) Process for Pro-ducing Essential Oil via Treatment With Supercritical Water and Essen-tial Oil Obtained by Treatment with Supercritical Water Int Patent App WO9953002A1

Mohammed E A Ayman A H E (2012) Pulsed electric fields for food processing technology In Eissa A A (ed) Structure and Function of Food Engineering Intech Open Rijeka Croatia pp 275ndash301

Mortazavi S V Eikani M H Mirzaei H Jafari M Golmohammad F (2010) Extraction of essential oils from Bunium persicum Boiss using superheated water Food and Bioproducts Processing 88 222ndash226

Muller G Frey W Sack M Schultheiss C Mayer H G Sigler J Kern M Gunther U (2007) Karlsruhe electroporation system KEA the success story of a technology transfer in the industry Research Center Karlsruhe-Nachrichten 39 153ndash158

Murga R Ruiz R Beltran S Cabezas J L (2000) Extraction of natu-ral complex phenols and tannins from grape seeds by using supercritical mixtures of carbon dioxide and alcohol Journal of Agricultural and Food Chemistry 48 3408ndash3412

Mushtaq M Sultana B Bhatti H N Asghar M (2015) RSM based opti-mized enzyme-assisted extraction of antioxidant phenolics from underuti-lized watermelon (Citrullus lanatus Thunb) rind Journal of Food Science and Technology 52 5048ndash5056

Nagendra K P Yang B Shi J Yu C Zhao M Xue S Jiang Y (2010) Enhanced antioxidant and antityrosinase activities of longan fruit pericarp by ultra-high-pressure assisted extraction processing Journal of Pharma-ceutical and Biomedical Analysis 51 471ndash477

Ndiomu D P Simpson C F (1988) Some applications of supercritical fluid extraction Analytica Chimica Acta 213 237ndash243

Nieto A Borrull F Pocurull E Marce R M (2010) Pressurized liquid extraction a useful technique to extract pharmaceuticals and personal-care products from sewage sludge Trends in Analytical Chemistry 29 752ndash764

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Niranjan K Hanmoungjai P (2004) Enzyme-aided aqueous extraction In Dunford N T Dunford H B (eds) Nutritionally Enhanced Edible Oil Processing AOCS Publishing Illinois

Oliveira D A Salvador A A Smania A Smania E F A Maraschin M Ferreira S R S (2013) Antimicrobial activity and composition profile of grape (Vitis vinifera) pomace extracts obtained by supercritical fluids Journal of Biotechnology 164 423ndash432

Ollanketo M Peltoketo A Hartonen K Hiltunen R Riekkola M L (2002) Extraction of sage (Salvia officinalis L) by pressurized hot water and conventional methods antioxidant activity of the extracts European Food Research and Technology 215 158ndash163

Olmedo R Nepote V Grosso N R (2014) Antioxidant activity of frac-tions from oregano essential oils obtained by molecular distillation Food Chemistry 156 212ndash219

Ong E S Len S M (2003) Pressurized hot water extraction of berberine baicalein and glycyrrhizin in medicinal plants Analytica Chimica Acta 482 81ndash89

Ordonez R M Cardozo M L Zampini I C Isla M I (2010) Evaluation of antioxidant activity and genotoxicity of alcoholic and aqueous bever-ages and pomace derived from ripe fruits of Cyphomandra betacea sendt Journal of Agricultural and Food Chemistry 58 331ndash337

Pare J J R Belanger J M R Stafford S S (1994) Microwave-assisted process (MAPtrade) a new tool for the analytical laboratory Trends in Ana-lytical Chemistry 13 176ndash184

Pascual-Marti M C Salvador A Chafer A Berna A (2001) Supercritical fluid extraction of resveratrol from grape skin of Vitis vinifera and deter-mination by HPLC Talanta 54 735ndash740

Patist A Bates D (2008) Ultrasonic innovations in the food industry from the laboratory to commercial production Innovative Food Science and Emerging Technologies 9 147ndash154

Pavlic B Naffati A Hojan T Vladic J Zekovic Z Vidovic S (in press) Microwave assisted extraction of wild apple fruit dustmdashproduction of polyphenol rich extracts from filter tea factory by-products Journal of Food Process Engineering doi 101111jfpe12508

Pawlowski T M Poole C F (1998) Extraction of chiabendazole and car-bendazim from foods using pressurized hot (subcritical) water for extrac-tion a feasibility study Journal of Agricultural and Food Chemistry 46 3124ndash3132

Petigny L Perino S Minuti M Visinoni F Wajsman J Chemat F (2014) Molecular sciences simultaneous microwave extraction and separation of volatile and non-volatile organic compounds of boldo leaves from lab to industrial scale International Journal of Molecular Sciences 15 7183ndash7198

Petigny L Perino-Issartier S Wajsman J Chemat F (2013) Batch and continuous ultrasound assisted extraction of boldo leaves (Peumus boldus Mol) International Journal of Molecular Sciences 14 5750ndash5764

Pilodist (2014) Thin Film Evaporation httpwwwpilodistdedistillation-by-thin-film-evaporation

Pinelo M Arnous A Meyer A S (2006) Upgrading of grape skins sig-nificance of plant cell wall structural components and extraction tech-niques for phenol release Trends in Food Science amp Technology 17 579ndash590

Pizzichemi M (2007) Application of pulsed electric fields to food treatment Nuclear Physics B 172 314ndash316

Posada L R Shi J Kakudaa Y Xueb S J (2007) Extraction of tocotrien-ols from palm fatty acid distillates using molecular distillation Separation and Purification Technology 57 220ndash229

Puertolas E Lopez N Saldana G Alvarez I Raso J (2010) Evaluation of phenolic extraction during fermentation of red grapes treated by a continuous pulsed electric fields process at pilot-plant scale Journal of Food Engineering 119 1063ndash1070

Puri M Sharma D Barrow C J (2012) Enzyme-assisted extraction of bio-actives from plants Trends in Biotechnology 30 37ndash44

Rajha H N Ziegler W Louka N Hobaika Z Vorobiev E Boechzelt H G Maroun R G (2014) Effect of the drying process on the intensification of phenolic compounds recovery from grape pomace using accelerated solvent extraction International Journal of Molecular Sciences 15 18640ndash18658

Ranveer R C Patil S N Sahoo A K (2013) Effect of different parameters on enzyme-assisted extraction of lycopene from tomato processing waste Food and Bioproducts Processing 91 370ndash375

Raverchon E Marco I D (2006) Review supercritical fluid extraction and fractionation of natural matter Journal of Supercritical Fluids 38 146ndash166

Raynie D E (2006) Modern extraction techniques Analytical Chemistry 78 3997ndash4004


Reichardt C (2003) Solvents and Solvent Effects in Organic Chemistry Wiley-VCH Publishers Germany

Richter B E Jones B A Ezzell J L Porter N L Avdalovic N Pohl C (1996) Accelerated solvent extraction a technology for sample prepara-tion Analytical Chemistry 68 1033ndash1039

Rodriguez R Jimenez A Fernandez-Bolanos J Guillen R Heredia A (2006) Dietary fibre from vegetable products as source of functional ingredients Trends in Food Science amp Technology 17 3ndash15

Rosenthal A Pyle D L Niranjan K (1996) Aqueous and enzymatic pro-cesses for edible oil extraction Enzyme and Microbial Technology 19 402ndash420

Rosenthal A Pyle D L Niranjan K Gilmour S Trinca L (2001) Com-bined effect of operational variables and enzyme activity on aqueous enzy-matic extraction of oil and protein from soybean Enzyme and Microbial Technology 28 499ndash509

Rovio S Hartanen K Holm Y Hiltunen R Riekkola M L (1999) Extraction of clove using pressurized hot water Flavour and Fragrance Journal 14 399ndash404

Sanchez-Zapata E Fuentes-Zaragoza E Fernandez-Lopez J Sendra E Sayas E Navarro C Perez-Alvarez J A (2009) Preparation of die-tary fiber powder from tiger nut (Cyperus esculentus) milk (ldquohorchatardquo) byproducts and its physicochemical properties Journal of Agricultural and Food Chemistry 57 7719ndash7725

Santos D T Veggi P C Angela M Meireles A (2012) Optimization and economic evaluation of pressurized liquid extraction of phenolic com-pounds from jabuticaba skins Journal of Food Engineering 108 444ndash445

Saravana P S Cho Y J Park Y B Woo H C Chun B S (2016) Struc-tural antioxidant and emulsifying activities of fucoidan from Saccharina japonica using pressurized liquid extraction Carbohydrate Polymers 153 518ndash525

Schieber A Stintzing F C Carle R (2001) By-products of plant food processing as a source of functional compoundsmdashrecent developments Trends in Food Science amp Technology 12 401ndash413

Sessa M Casazza A A Perego P Tsao R Ferrari G Donsigrave F (2012) Exploitation of polyphenolic extracts from grape marc as natural anti-oxidants by encapsulation in lipid-based nano delivery systems Food and Bioprocess Technology 6 2609ndash2620

Shang Y F Cha K H Lee E H Pan C H Um B H (2016) Optimiza-tion bio accessibility of tricin and antioxidative activity of extract from black bamboo leaves Free Radicals and Antioxidants 6 64ndash71

Sharma A Khare S K Gupta M N (2002) Enzyme-assisted aqueous extraction of peanut oil Journal of the American Oil Chemistsrsquo Society 79 215ndash218

Shi J Kakuda Y Zhou X Mittal G Pan Q (2007a) Correlation of mass transfer coefficient in the extraction of plant oil in a fixed bed for super-critical CO2 Journal of Food Engineering 78 33ndash40

Shi J Kassana L S Kakuda Y (2007b) Supercritical fluid technology for extraction of bioactive components In Shi J (ed) Functional Food Ingredients and Nutraceuticals Processing Technology CRC Press Boca Raton FL pp 3ndash44

Shi J Mittal G Kim E Xue S J (2007c) Solubility of carotenoids in supercritical CO2 Food Reviews International 23 341ndash371

Shi J Yi C Ye X Xue S Jiang Y Ma Y Liu D (2009) Effects of supercritical CO2 fluid parameters on chemical composition and yield of carotenoids extracted from pumpkin LWT ndash Food Science and Technol-ogy 43 39ndash44

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Shi J Yi C Ye X Xue S Jiang Y Maa Y Liu D (2010) Effects of supercritical CO2 fluid parameters on chemical composition and yield of carotenoids extracted from pumpkin LWT ndash Food Science and Technol-ogy 43 39ndash44

Shui G Leong L P (2006) Residue from star fruit as valuable source for functional food ingredients and antioxidant nutraceuticals Food Chem-istry 97 277ndash284

Sihvonen M Jarvenpaa E Hietaniemi V Huopalahti R (1999) Advances in supercritical carbon dioxide technologies Trends in Food Science amp Technology 10 217ndash222

Silva L V Nelson D L Drummond M F B Dufosse L Gloria M B A (2005) Comparison of hydrodistillation methods for the deodorization of turmeric Food Research International 38 1087ndash1096

Singh R P Murthy K N C Jayaprakasha G K (2002) Studies on the anti-oxidant activity of pomegranate (Punica granatum) peel and seed extracts using in vitro models Journal of Agricultural and Food Chemistry 50 81ndash86

Singh R K Sarker B C Kumbhar B K Agrawal Y C Kulshreshtha M K (1999) Response surface analysis of enzyme-assisted oil extraction factors for sesame groundnut and sunflower seeds Journal of Food Science and Technology 36 511ndash514

Sitzmann W Munch E W (1988) The elcrack procedure a new procedure for the processing of animal raw materials The Meat Meal Industry 40 22ndash28

Someya S Yoshiki Y Okubo K (2002) Antioxidant compounds from bananas (Musa cavendish) Food Chemistry 88 411ndash417

Soto-Ayala R Luque-de-Castro M D (2001) Continuous subcritical water extraction as a useful tool for isolation of edible essential oil Food Chem-istry 75 109ndash113

Sowbhagya H Chitra V (2010) Enzyme-assisted extraction of flavorings and colorants from plant materials Critical Reviews in Food Science and Nutrition 50 146ndash161

Suslick K S Doktycz S J (1990) The effects of ultrasound on solids In Mason T J (eds) Advances in Sonochemistry Vol 1 JAI Press New York NY pp 197ndash230

Tabaraki R Ghadiri F (2016) Comparative study of extraction methods for pistachio hull antioxidants by multiple assays Journal of Applied Chem-istry 37 19ndash29

Technoforce (2014) Short Path (Molecular) Distillation Units httpwwwtechnoforcenetshort-path-molecular-distillation-unitshtml

Temelli F Guclu-Ustundag O (2005) Supercritical Technologies for Further Processing of Edible Oils Baileyrsquos Industrial Oil and Fat Products John Wiley amp Sons Inc Texas

Thirugnanasambandham K Sivakumar V (2017) Microwave assisted extraction process of betalain from dragon fruit and its antioxidant activi-ties Journal of the Saudi Society of Agricultural Sciences 16 41ndash48

Toepfl S Heinz V Knorr D (2007) High intensity pulsed electric fields applied for food preservation Chemical Engineering and Processing 46 537ndash546

Toepfl S Mathys A Heinz V Knorr D (2006) Review potential of high hydrostatic pressure and pulsed electric fields for energy efficiency and environmentally friendly food processing Food Reviews International 22 405ndash423

UIC GmbH (2014) Thin Film Evaporation httpwwwuic-gmbhdeenbasicsthin-film-evaporationhtml

Vallverdu-Queralt A Odriozola-Serrano I Oms-Oliu G Lameula-Raven-tos R M Elez-Mortinez P Martin-Belloso O (2013) Impact of high

intensity pulsed electric fields on carotenoids profile of tomato juices made of moderate intensity pulsed electric field treated tomatoes Food Chem-istry 141 3131ndash3138

Vankar P S (2004) Essential oils and fragrances from natural sources Reso-nance 9 30ndash41

Vilkhu K Mawson R Simons L Bates D (2008) Applications and oppor-tunities for ultrasound assisted extraction in the food industry a review Innovative Food Science and Emerging Technologies 9 161ndash169

Vinatoru M Toma M Filip P Achim T Stan N Mason T J Mocanu P Livezeanu G Lazurca D (1998) Ultrasonic Reactor Dedicated to the Extraction of Active Principles from Plants Romanian Patent No 98-01014

Vorobiev E Jemai A B Bouzrara H Lebovka N I Bazhal M I (2005) Pulsed electric field assisted extraction of juice from food plants In Bar-bosa-Canovas G Tapia M S Cano M P (eds) Novel Food Processing Technologies CRC Press New York NY pp 105ndash130

Vorobiev E Lebovka N I (2006) Extraction of intercellular components by pulsed electric fields In Raso J Heinz V (eds) Pulsed Electric Field Tech-nology for the Food Industry Fundamentals and Applications Springer New York NY pp 153ndash194

Wang Y You J Yu Y Qu C Zhang H Ding L Zhang H Li X (2008) Analysis of ginsenosides in Panax ginseng in high pressure microwave-assisted extraction Food Chemistry 110 161ndash167

Wang L Weller C L (2006) Recent advances in extraction of nutraceuticals from plants Trends in Food Science amp Technology 17 300ndash312

Wijngaard H Brunton N (2009) The optimization of extraction of antioxi-dants from apple pomace by pressurized liquids Journal of Agricultural and Food Chemistry 57 10625ndash10631

Xu G H Chen J C Liu D H Zhang Y H Jiang P Ye X Q (2008) Minerals phenolic compounds and antioxidant capacity of citrus peel extract by hot water Journal of Food Science 73 C11ndashC18

Xu X Jacobsen C Nielsen N S Heinrich M T Zhou D (2002) Purification and deodorization of structured lipids by short path dis-tillation European Journal of Lipid Science and Technology 104 745ndash755

Yang B Jiang Y Zhao M Shi J Wang L (2008) Effects of ultrasonic extraction on the physical and chemical properties of polysaccharides from longan fruit pericarp Polymer Degradation and Stability 93 268ndash272

Yi C Shi J Xue S J Jiang Y M Li D (2009) Effects of supercritical fluid extraction parameters on lycopene yield and antioxidant activity Food Chemistry 113 1088ndash1094

Yu H B Ding L F Wang Z Shi L X (2014) Study on extraction of poly-phenol from grape peel microwave-assisted activity Advanced Materials Research 864ndash867 520ndash525

Zhang G Y Liu J Liu Y F (2013) Concentration of omega-3 polyunsatu-rated fatty acids from oil of Schizochytrium limacinum by molecular distil-lation optimization of technological conditions Industrial amp Engineering Chemistry Research 52 3918ndash3925

Zheng X Wang X Lan Y Shi J Xue S J Liu C (2009) Application of response surface methodology to optimize microwave-assisted extraction of silymarin from milk thistle seeds Separation and Purification Technol-ogy 70 34ndash40

Zougagh M Valcarcel M and Rios A (2004) Supercritical fluid extraction A critical review of its analytical usefulness Trends in Analytical Chemis-try 23 399ndash 405

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unit delivers several unutilizable waste materials which comprises mainly seeds peel and stones Among them the fruit peel exhib-ited significant antioxidant activity which is around 2- to 27-fold higher than fruit pulp (Someya et al 2002 Guo et al 2003 Goulas and Manganaris 2012) The inexpensive source of antioxidants was reported to be obtained from by-products of several fruits viz star fruit (Shui and Leong 2006) grapes (Lafka et al 2007) citrus fruits (Xu et al 2008) and pomegranate (Singh et al 2002)

The crude extracts obtained from several plant materials were the rich source of phenolic compounds and they have potential applica-tion as preservatives and also used in development of several func-tional foods and nutraceuticals (Marja et al 1999) Therefore the consumption of antioxidant rich foods will scavenge the formation of free radicals and it also helps in preventing the oxidative stress-related diseases (Joshi et al 2012) Fruits and vegetables found to possess several non-digestible components and phytoconstituents in the form of antioxidants which significantly contribute towards the several added health benefits These antioxidants are nowadays widely used as functional ingredients in many processed foods The marketing trend in this field is quiet competitive and therefore the development of new type of quality ingredients is a big challenge for the food processing industries

The term lsquoby-productrsquo means reusuable plant wastes which are having a good market value (Sanchez-Zapata et al 2009) Globally the large amounts of plant wastes were generated from several food processing industries which were estimated to be around 800 000 tyear (Ayala-Zavala et al 2010) The wastes obtained from such industries are highly perishable and they will pose serious environ-mental problems to society (Arvanitoyannis and Varzakas 2008) Table 1 shows the by-products generated from fruits and vegetables processing industries and these by-products comprises mainly of skins seeds stems leaves wastewaters and unusable pulp which are normally discarded after processing (Ajila et al 2007) These by-products amount contributes to more than 40 for plant foods such as artichoke asparagus cactus pear fruit mango orange papaya pineapple red chicory and tiger nuts

The plant by-products are considered to be one of the cheap sources of several antioxidants The extraction of antioxidants from such plant by-products is very much essential for developing

functional food products Higher antioxidant extraction methods are available for use at a commercial level These methods were found to be safe eco-friendly and possess non-carcinogenic effect when compared to synthetic methods The productionrecovery of high-value compounds such as antioxidants is increasingly being considered through the biorefinery concept Bozell and Petersen (2010) Therefore in this review the recent methods in extraction of antioxidants from plant by-products processing industries were discussed and commercial method of antioxidants extraction at a large-scale level and also comparative efficacy of different extraction methods were highlighted The process systems along with industrial applications for non-conventional method of antioxidants were dis-cussed Therefore the food industry can choose the efficient method of extracting functional components from several plant by-products on a large-scale basis and they can deliver several functional food products to the market

Methods of Extraction of Antioxidants

Extraction is a separation process used for separating solutes ie bioactive constituents from solutions using specific solvents by adopting standard procedures (Handa et al 2008) The main pur-pose of this extraction method is to separate the soluble solutes from the plant by-products for performing the efficient extraction process The crude extracts obtained by using these methods con-tain complex mixtures of several plant metabolites viz alkaloids glycosides phenolics terpenoids and flavonoids These extracts are quiet being used as a medicinal agent in the form of tinctures and fluid extracts There are several methods that are available to effi-ciently extract antioxidants from plant by-products of processing industries and these methods are discussed with their commercial applications

Conventional extraction techniquesClassicalconventional extraction techniques are being used at a small scale level to extract bioactive components from several plant materials These techniques are usually based on the extraction effi-ciency of different solvents which are being used for this purpose It

Table 1 Amount of by-products generated from fruit and vegetable processing industry

Fruitvegetable By-products Edible part Reference

Agave 40 (rind and pith) 60 Iniguez-Covarrubias et al (2001)Apple 11 (pulp and seed core) 89 Ayala-Zavala et al (2010)Artichoke Around 60 (outer bracts receptacles and stems) 40 Llorach et al (2002)Asparagus Up to 40ndash50 (spear) 50ndash60 Rodriguez et al (2006)Banana Up to 30 (peel) 70 Schieber et al (2001)Cactus pear cladodes 20 (spines glochids and peel) 80 Bensadon et al (2010)Cactus pear fruit 45 (spines glochids peel and unusable pulp) 65 Bensadon et al (2010)Carrot 30ndash40 (pomace) 60ndash70 Schieber et al (2001)Cyphomandra betacea 15ndash35 (skin pulp and seeds) 65ndash85 Ordonez et al (2010)Guava 10ndash15 (peel and seeds) 85ndash90 Schieber et al (2001)Mandarin 16 (peels) 84 Ayala-Zavala et al (2010)Mango 135 (seeds) 11 (peels) and 179 (unusable pulp) 58 Ayala-Zavala et al (2010)Orange 66 (peel) 44 Li et al (2006)Papaya 65 (seeds) 85 (peels) and 321 (unusable pulp) 53 Ayala-Zavala et al (2010)Passion fruit gt75 (rind and seeds) 25 Schieber et al (2001)Pineapple 91 (core) 135 (peels) 149 (top) and 145 (pulp) 48 Ayala-Zavala et al (2010)Potato 15ndash40 (peel) 60ndash85 Schieber et al (2001)Tomato 3ndash7 (peel and seeds) 93ndash97 Schieber et al (2001)Tiger nuts (lsquoChufarsquo) Up to 60 (solid and liquid wastes) 40 Sanchez-Zapata et al (2009)

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