Journal of Food Engineering 112 (2012) 29–37

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Journal of Food Engineering

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Preparation and characterization of non-aqueous extracts from chilli (Capsicumannuum L.) and their microencapsulates obtained by spray-drying

Andrea Yazmin Guadarrama-Lezama a, Lidia Dorantes-Alvarez a, Maria Eugenia Jaramillo-Flores a,César Pérez-Alonso b, Keshavan Niranjan c, Gustavo Fidel Gutiérrez-López a, Liliana Alamilla-Beltrán a,⇑a Departamento de Graduados e Investigación en Alimentos, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Carpio y Plan de Ayala s/n, CP 11340 México,DF, Mexicob Facultad de Química, Universidad Autónoma del Estado de México, Paseo Tollocan esq. Paseo Colón s/n, CP 50120 Toluca, Estado de México, Mexicoc Department of Food and Nutritional Sciences, University of Reading, Whiteknights, P.O. Box 226, Reading G66AP, UK

a r t i c l e i n f o a b s t r a c t

Article history:Received 16 November 2011Received in revised form 1 March 2012Accepted 10 March 2012Available online 30 March 2012

Keywords:ChilliCarotenoidsNon-aqueous extractAntioxidant activityMicroencapsulates

0260-8774/$ - see front matter � 2012 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.jfoodeng.2012.03.032

⇑ Corresponding author. Tel.: +52 5557296000x624E-mail address: liliana.alamilla@gmail.com (L. Alam

Antimicrobial, antioxidant, and pro-vitamin properties have been attributed to Capsicum based on thecarotenoid and polyphenolic compound content. The aim of this study was to obtain and characterizenon-aqueous extracts of Capsicum annuum L. (chilli) using three different oils (corn, sunflower, and saf-flower) as well as their microencapsulates. Corn extract showed better antioxidant activity and totalcarotenoid content (as b-carotene) than sunflower and safflower extracts. The extracts were encapsulatedby spray-drying with a biopolymers:extract-solution ratio of 4:1 (w/w). The biopolymers were gumArabic and maltodextrin. In addition, the encapsulation efficiency, mean particle size, morphology, wateractivity, moisture content, and stability were evaluated for the microcapsules. The retention of antioxi-dant activity after encapsulation varied from 76% to 80% of its activity in the oily extract, whereas thepreservation of carotenoids in microcapsules was between 84% and 86%.

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1. Introduction

Capsicum annuum L. (chilli) is widely used for culinary andindustrial purposes due to its characteristic flavour and colour(Topuz et al., 2009). Antimicrobial, antioxidant/free-radical, andpro-vitamin properties have been attributed to C. annuum, givenits content of polyphenolic compounds and carotenoids(Acero-Ortega et al., 2005; Hornero-Mendez et al., 2000; Topuzand Ozdemir, 2007). Chillies are good sources of carotenoids;approximately 25 different carotenoids have been identified inC. annuum L. grossum Sendt, including b-carotene, a-carotene,b-cryptoxanthin, zeaxanthin, luteine, capsanthin, capsorubin,and cryptocapsin, which are the most abundant components(Collera-Zúñiga et al., 2005). Provitamin A, carotenoids (b-carotene, a-carotene, and b-cryptoxanthin), and xanthophyllsmay be important for the prevention of age-related macular degen-eration and cataracts (Matsufuji et al., 1998; Seddon et al., 1994).The antioxidant activity of the carotenoid pigments is due to thefollowing characteristics of their structure: (a) the polyene carbonchain, which permits the incorporation of free radicals by additionmechanisms, which slows propagation, and (b) functional groupson the b-rings, such as keto groups as well as the esterified form,

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64.illa-Beltrán).

which potentiate the antioxidant activity (Pérez-Gálvez andMínguez-Mosquera, 2002). Therefore, the use of chilli peppers asingredients could be a useful alternative for designing functionalfoods that contain high antioxidant activity. More recently, therehas been interest in extracting bioactive compounds, such ascarotenoids from vegetables and fruits, because of the potentialof these substances as functional ingredients in food formulationsand nutritional supplements (Marete et al., 2009). Because of theirhydrophobic nature, carotenoids are generally extracted fromplant materials using organic solvents (Craft, 1992). The carote-noids in Capsicum are commonly extracted with hexane becauseof the low-polarity nature of these compounds. Recently, Richinset al. (2010) compared two methods for carotenoids extractionfrom Capsicum: the first by using hexane, and the second by meansof supercritical fluid extraction (SFE) with CO2. The efficiency ofextraction by SFE was 31% greater than that obtained with hexane.In order to improve this result, ethanol was used in addition to SFEfor recovering the carotenoids. Although new methods for extrac-tion of bioactive compounds have been developed, the use ofsolvents, which cannot be consumed, has not been totally eradi-cated. Solvents used for carotenoid extraction must be removedfrom the extracts before they can be included in foods, which re-quires an additional step in the process. Therefore, new methodsfor extraction and preservation of the antioxidant properties ofcarotenoids are needed. In this context, the use of edible oils as

30 A.Y. Guadarrama-Lezama et al. / Journal of Food Engineering 112 (2012) 29–37

extraction media may be a novel option for non-aqueous extrac-tion processes that have potential advantages in health, safety,and ecologically-related issues. To date, the use of edible oils asnon-polar dissolvents for the extraction of carotenoids from Capsi-cum has not been explored. Once carotenoids are extracted, isom-erization (Xianquan et al., 2005) and oxidative reactions may occuras a consequence of the exposure of carotenoids to ambient tem-perature and oxygen as well as the presence of unsaturated doublebonds in the molecular structure of carotenoids, which causes mol-ecule fractioning and the production of apocarotenoids (Maokaet al., 2001) or epoxides. For this reason, the extracts must becarefully handled. However, one possible approach for minimizingor inhibiting deteriorative reactions of carotenoids in extracts ofCapsicum is by protecting the extracts in microcapsules.

Microencapsulation through spray-drying is an effective tech-nique that allows for the protection of food ingredients, such ascarotenoids (Rocha et al., 2012) and polyphenols (Fang and Bhan-dari, 2010), from chemical deterioration and environmental factorsby converting liquids into functional powders that can be incorpo-rated into various formulations. This protection was performedusing wall materials, such as sugars, gums, proteins, natural andmodified polysaccharides, lipids, and synthetic polymers (Gharsa-llaoui et al., 2007; Fang and Bhandari, 2010; Rocha et al., 2012).It has been reported that both protein and lipid fractions that arepart of the molecular structure of gum Arabic provide emulsifyingproperties, film formation, low viscosity and high water solubility(Yadav et al., 2007). Similarly, it has been postulated that morehydrophobic polypeptide chains adsorbed at the surface of the oildroplets with hydrophilic carbohydrate blocks attached to thechain protruding out into solution can provide a stronger stericbarrier that prevents droplet aggregation and coalescence (Islamet al., 1997). Maltodextrin exhibits various favourable characteris-tics, including high hydrosolubility, low emulsifying capacity, lowretention of volatiles, and high protection against oxidation (Buffoand Reineccius, 2000). During microencapsulation by spray-drying,dry particles are obtained in the form of powders or agglomeratesthat can enhance the shelf-life of food products (Soottitantawatet al., 2005). Based on these studies, the objective of this workwas to explore the extraction of carotenoids from chilli peppersby using non-aqueous media, such as edible oils, and the preserva-tion of the extracted compounds in the form of microcapsules,which could be used as an ingredient in food processing.

2. Materials and methods

2.1. Materials

The C. annuum L. grossum Sendt (chilli) used for this work aswell as the corn (Maceite�), sunflower (Patrona�) and safflower(Oleico�) oils were purchased from a local market in Mexico City,Mexico. The wall materials used for microencapsulation weregum Arabic, food grade E 414 (Distribuidora Química LEFE S.A deC.V., Mexico City, Mexico) and maltodextrin 20 DE (CPI Ingredien-tes S.A de C.V, State of Mexico, Mexico). Potassium persulfate(K2S2O8) and 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid(ABTS) radical were purchased from Sigma Chemical Company,St. Louis, MO, USA.

2.2. Methods

2.2.1. Extraction of carotenoids from C. annuum L. grossum Sendt(chilli)

Dried chilli peppers were selected and manually cleaned toeliminate foreign matter. The stems were also removed prior todry grinding. The resulting powder was sieved using a 25 mesh

(Tyler Standard Sieve Series, Mentor, Ohio, USA). Extraction wasperformed using corn, sunflower, and safflower oils at three differ-ent temperatures (60, 70, and 80 �C) and two mixing times (5 and10 min). In all cases, the chilli powder and oil was mixed at a 1:2(w/v) ratio, respectively, at 1100 rpm in a Thermomix (TM 31, Vor-werk, Spain). Refined and comestible oils were used for extraction.Corn, sunflower, and safflower oils have 12%, 10%, and 7.4%saturated fatty acids, respectively; palmitic and stearic acids arepresent in the highest concentration in the four oils. In addition,these oils contain 88%, 90%, and 92.6% unsaturated fatty acids,respectively, with oleic and linoleic being the most abundant.The obtained extracts were filtered through cheesecloth and subse-quently centrifuged (Allegra™ X-12R Beckman Coulter, USA) at3700 rpm for 15 min to separate the solids and to obtain thenon-aqueous extracts of chilli (NAEC). The NAEC were stored inamber glass recipients at 10 �C for further use.

2.2.2. Determination of antioxidant activity of NAEC using the2,20-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS)�+

methodThe antioxidant activity of the extracts was determined by

diluting 200 lL NAEC with 800 lL of acetone (Fermont, México).Of this solution, 10 lL was reacted with 990 lL of ABTS�+ radical,and the absorbance was measured at 734 nm (Pastrana-Bonillaet al., 2003). All measurements were performed in triplicate, andthe average ± standard deviation (SD) was reported. The percentinhibition was calculated as follows:

%Inhibition ¼ Ast0 � Astf

Ast0 �Adt0�Adtf

Adt0

h i� � ð1Þ

where Ast0 and Astf are the absorbance of sample at initial and finaltimes; Adt0 and Adtf are the absorbance of dissolvent at initial andfinal times.

A standard curve was constructed using different concentra-tions of Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carbox-ylic acid; Sigma Chemical Company, St. Louis, MO, USA). Theresults were presented as lmol Trolox/mL. The antioxidant activitydetermined for pure oils were subtracted from the antioxidantactivity of the extracts.

2.2.3. The Folin testThe Folin test for NAEC and NAEC microcapsules was determined

using the Folin–Ciocalteau reagent (Sun et al., 2007). The reagentwas diluted 10 times with deionized water. Each NAEC was dilutedat a ratio of 1:5 with ethanol, and a 0.1 mL aliquot was mixed with0.75 mL of the diluted Folin–Ciocalteau reagent. After the reactionsolution had been incubated at room temperature (RT) for 5 min,0.75 mL (60 g/L) sodium bicarbonate solution was added and thor-oughly mixed. The mixture was incubated at RT for 90 min and thenfiltered by using a 0.45 lm syringe filter (Corning, Germany). Theabsorbance of the solution was then determined at 750 nm. Gallicacid was used as standard reference and the results were expressedas gallic acid equivalents (lg) per mL of extract.

2.2.4. Extraction of carotenoids with fatty acidsCarotenoid extracts of chilli powder were obtained through

homogenization with stearic and oleic acids at 70 �C for 5 min toevaluate carotenoid affinity with saturated or unsaturated fattyacids. This temperature of extraction was selected due to the factthat stearic acid is in a solid state below 70 �C.

2.2.5. Preparation of oil-in-water (o/w) emulsions and the spray-drying process

Gum Arabic (GA; 10 g) and maltodextrin (MD; 10 g) weredissolved in 100 mL of distilled water using a mixer (Stir-Pak

A.Y. Guadarrama-Lezama et al. / Journal of Food Engineering 112 (2012) 29–37 31

Laboratory Stirrer, Cole Palmer Instrument Co., Model 4554-00,USA). This solution was stored at 10 �C overnight to ensure com-plete rehydration of the polymers (Pérez-Alonso et al., 2008). Threeoil-in-water (o/w) emulsions were prepared by adding each of thethree different non-aqueous extracts prepared with corn, sun-flower, and safflower oil drop-by-drop to the biopolymeric solu-tion, while homogenizing the solution with an Ultra-Turrax(M45, USA) at 10,000 rpm, with U = 0.05 (relation of the volumeof the dispersed phase to the total volume of the emulsion) and abiopolymers:extract ratio of 4:1. Once the oil was added, homoge-nization was continued for an additional 3 min. An ice bath wasused during the preparation of the emulsions with the goal ofmaintaining temperature under 30 �C in order to avoid instabilityof the system (Koberstein-Hadja and Dickinson, 1996). The emul-sion was fed into the spray-dryer (Mobile Minor™ 2000, GEA Niro,Denmark) using a peristaltic pump (Watson-Marlow 520S, USA).The spraying system was a pneumatic nozzle with parallelarrangement in respect to the air flow. The inlet and outlet temper-atures of drying air used for the microencapsulation were160 ± 2 �C and 70 ± 2 �C, respectively, and an air pressure of0.4 kg/cm2 was used for spraying. The liquid feed rate was13.3 mL/min. The microencapsulated NAEC were collected andplaced into plastic bags, hermetically sealed, and stored at25 ± 2 �C in the absence of light until further characterization anal-yses were performed.

2.2.6. Evaluation of antioxidant activity and Folin test ofmicroencapsulated NAEC

Two grams of microcapsules were dissolved in 3 mL of bidis-tilled water at 50 �C by stirring for 3 min in a Vortex (Maxi MixII, Barnstead Thermolyne, USA) followed by the addition of10 mL of hexane–isopropanol (3:1) (Hardas et al., 2000). The mix-ture was vortexed for an additional 5 min and centrifuged at3600 rpm for 15 min at 10 �C. The mixture NAEC-solvent phasewas separated using a Pasteur pipette and placed into a 50 mLround-bottom flask. The solvent was evaporated to a final volumeof 2 mL at 50 �C using a rotary vacuum evaporator (Buchi R-210/R-215, Flawil, Switzerland). Antioxidant activity and the Folin testwere determined by using the ABTS�+ free radical scavengingmethod described in Section 2.2.2 and the Folin test describedin Section 2.2.3.

2.2.7. Determination of total carotenoid content in NAEC andmicroencapsulated NAEC

The carotenoid content (CT) as well as red (CR) and yellow(CY) isochromatic fractions were spectrophotometrically deter-mined using the method proposed by Hornero-Méndez andMínguez-Mosquera (2001). This method consists of reading theabsorbance of the carotenoid solutions, which were obtained bymixing 0.4 mL of NAEC with 2 mL of acetone, at 472 and 508 nm.In the case of microencapsulated NAEC, the first step was toseparate the oil fraction (containing carotenoids) from the biopoly-mers (GA and MD) as described in Section 2.2.6. Removal of thehexane:isopropanol was performed by gasing out using nitrogen.The oil fraction was finally diluted with acetone and its absorbanceat 472 and 508 nm was evaluated. In this work, total carotenoidcontent is expressed as b-carotene content.

2.2.8. Evaluation of water activity and moisture content ofmicroencapsulated NAEC

The water activity of the microcapsules was determined usingan Aqualab (Decagon Devices, Model 4 TE, USA) at 25 �C. Moisturecontent of the microcapsules was determined gravimetricallyusing the official AOAC method (AOAC, 1995).

2.2.9. Morphology of microcapsules by scanning electron microscopy(SEM)

The morphology and appearance of the surface of microcap-sules of NAEC obtained by spray-drying were examined with ascanning electron microscope (SEM; Jeol, Model JSM-5800LV,Japan). Samples of microcapsules of NAEC were sprayed with apaintbrush to a metal die, which had a two-sided adhesive carbontape attached to it (Ted Pella, Redding, California, USA). The sam-ples were subsequently coated with gold ions (Rosenberg andYoung, 1993) using a magnetron sputter coater (Denton Vacuum,Model Desk II, USA) at 13.3 kPa and 15 mA. The coated sampleswere then observed using SEM, which was operated at an acceler-ating voltage of 15 kV (Jafari et al., 2007), and the correspondingimages were captured.

2.2.10. Determination of extractable and non-extractable NAEC inmicrocapsules

In order to determine the non-extractable fraction of NAEC,which was the percent of encapsulated NAEC, 2 g of microcapsuleswere added to 20 mL of hexane. Agitation was performed for 5 minto avoid transfer of the NAEC from the internal part to the outerpart of the microcapsules. Once agitation concluded, the powderand the solvent were separated by filtration through grade 1 What-man filter paper and the residual solid was washed out with 5 mLof solvent. The filtered solution was transferred to a round-bottomflask for complete evaporation of the solvent using the rotary vac-uum evaporator (Buchi R-210/R-215, Flawil, Switzerland). Theresidual solids were dissolved following the procedure describedin Section 2.2.6, which included complete evaporation of the sol-vent to determine the amount of encapsulated NAEC or non-extractable fraction (Drusch and Berg, 2008; Calvo et al., 2010).The percent of encapsulated NAEC was calculated using:

Eo ¼ AT � AS

AT x100 ð2Þ

where AT and AS are the total content of NAEC and the content ofextractable portion of encapsulated NAEC, respectively.

2.2.11. Encapsulation efficiency (EE)The EE was calculated as the ratio between the initial content of

total carotenoid present in the capsules and the total carotenoidcontent in the extract used to produce them. The EE was analysedbased on b-carotene as a target chemical compound that has beenreported as the major component in chilli (Collera-Zúñiga et al.,2005). The total carotenoid content in extracts and microcapsules(as b-carotene content) was determined using the procedure de-scribed in Section 2.2.7.

2.2.12. Determination of the mean particle size of microcapsulesA particle size analyzer (Mastersizer 2000, Malvern Instruments

Ltd., Malvern, Worcestershire, UK) was used to determine theSauter mean diameter (d3,2) of the particles (Jafari et al., 2007).

2.2.13. Stability tests for microencapsulatesThe stability of microencapsulated NAEC was determined by

measuring the antioxidant activity (Section 2.2.6) and water activ-ity (Section 2.2.8) of the microcapsules after 60 d of storage at20 ± 5 �C.

2.2.14. Statistical analysisA one-way analysis of variance (ANOVA) with 2a = 0.05 signifi-

cance level was applied to all results. The Tukey’s test was used tocompare differences between mean values of individual samples(Minitab 15.0 software, Minitab� Inc., USA).

32 A.Y. Guadarrama-Lezama et al. / Journal of Food Engineering 112 (2012) 29–37

3. Results and discussion

3.1. Extraction conditions, antioxidant activity, and Folin test

Data of antioxidant activities from all extraction conditions areshown in Table 1. The best extraction of carotenoids and optimalantioxidant activity in the extracts was obtained when extractionwas conducted at 60 �C for 5 min while mixing at 1100 rpm. Thehighest temperatures (70 and 80 �C) and longer extraction timeshad a negative effect on the antioxidant activity of NAEC. The typeof oil used for the extractions influenced the antioxidant activityand exhibited different affinities for the carotenoids (Table 2).The extract obtained with corn oil at 60 �C and 5 min had signifi-cantly (p 6 0.05) higher antioxidant activity (78.5 ± 0.7 lmol-Trol-ox/mL) than the sunflower and safflower oil extracts (67.3 ± 1.1and 51.7 ± 0.1 lmol-Trolox/mL, respectively). Similar results wereobserved for the yellow and red fractions and total carotenoid con-tent for oily extracts of corn, sunflower, and safflower, respectively(Table 2). The antioxidant activities found for pure oils were20.9 ± 0.8, 17.8 ± 0.5, and 13.1 ± 0.6 lmol-Trolox/mL for corn, sun-flower and safflower oils, respectively, and were subtracted fromthe antioxidant activity values reported for the extracts.

Carotenoids are non-polar compounds that are soluble in non-polar solvents, oils, and fats. These are present in plants in freeform or esterified (most of them). The hydrophobicity, stability,and antioxidant activity of the carotenoids depend on the type offatty acid to which the carotenoid is esterified (Ramakrishnanand Francis, 1979; Schweiggert et al., 2007; HongFei et al., 2010).However, capsanthin as well as its various esters inhibit the oxida-tion process in a similar manner to unesterified capsanthin, sug-gesting that the radical scavenging ability is not influenced byesterification (Matsufuji et al., 1998). The composition, degree ofunsaturation, and the length of the fatty acid chains of different oilshave a strong influence on their affinity by carotenoids, and there-fore the extracts obtained with each type of oil have a differentcomposition of carotenoids and consequently a different antioxi-dant activity. Corn oil, which contains a higher proportion of satu-rated fatty acids (12%) compared to sunflower and safflower oils(10% and 7.4%, respectively), is a better media for extracting carote-noids with antioxidant activity.

The antioxidant activity of chilli extracts prepared using stearicacid (18C-saturated acid) as extractive media was 90.2 ± 2.5 lmol-Trolox/mL, whereas extracts prepared with oleic acid (18C-unsatu-rated acid) had an antioxidant activity of 63.1 ± 3.5 lmol-Trolox/

Table 1Conditions of extraction, antioxidant activity, and Folin test of NAEC.

Oils used for extraction Temperature (�C) Time (min)

Corn 60 560 1070 570 1080 580 10

Sunflower 60 560 1070 570 1080 580 10

Safflower 60 560 1070 570 1080 580 10

Statistical analysis was performed by the type of oil used, and different le

mL. These results suggested that saturated fatty acids had a betteraffinity for carotenoids and exhibited enhanced stability comparedto extracts obtained by using unsaturated fatty acids, despite bothtypes having hydrocarbon chains of 18 carbon atoms. Carotenoidsconsist of a skeleton of 40 unsaturated carbon atoms, which provideshydrophobic specificity, and differences in the antioxidant activity ofextracts may be due to a higher chemical affinity of carotenoids forsaturated fatty acids than for unsaturated fatty acids in the oils. Thismay be due to differences in the molecular conformation ofsaturated and unsaturated fatty acids, which have one or more rigidtorsions in their hydrocarbon chains due to the inability to presentbond rotation. In the case of saturated fatty acids, the extended form(linear) configuration prevails because this structure has the lowestenergy (Lehninger et al., 1995; Kaneko et al., 1998).

Hyeon and Young (2008) evaluated the antioxidant activity ofseed and pericarp of red pepper. Extraction was performed with70% ethanol for 3 h, and antioxidant activity was measured usingvarious chemical assays, including the ABTS�+ method. The seedshowed a radical scavenging activity of 29% at 1000 lg/mL extract,while pericarp had 51% activity. In our study, the NAEC of corn,sunflower, and safflower oils showed 90%, 75%, and 60% radicalscavenging by ABTS�+, respectively. The values observed by Hyeonand Young (2008) were lower than those obtained with NAEC,which may be due to the different mechanisms of action that phe-nolic compounds, flavonoids, and carotenoids have in the presenceof the ABTS radical. The NAEC were obtained at moderate temper-ature and extraction time (60 �C and 5 min), which further reducedthe possibility of compound degradation and represents a techno-logical advantage for food-related applications, since volatile sol-vents were not used for the extraction.

Table 1 shows the results of the Folin test and antioxidant activ-ity, which demonstrated that the highest temperature used forextraction (80 �C) and longer time to homogenization (10 min)caused a negative effect on the compounds detected. The highestantioxidant activity was observed in extracts made with corn oil.Therefore, the compounds detected by the Folin reagent play animportant role in the antioxidant activity of non-aqueous extractsof chilli.

3.2. Antioxidant activity, carotenoid content, and Folin test ofmicroencapsulated NAEC

All microencapsulated NAEC collected from the drier retained76–80% of the antioxidant activity of the respective extracts (Table

Antioxidant Activity ofNAEC (lmol Trolox/mL)

Folin test of NAEC expressedas (lg gallic acid/mL)

78.5 ± 0.7a 57.3 ± 0.7a

83.1 ± 2.0a 63.5 ± 0.6b

68.2 ± 1.6b 40.6 ± 0.4c

55.9 ± 0.5c 55.8 ± 1.4a

61.3 ± 2.3d 45.7 ± 0.4d

52.2 ± 2.4e 47.4 ± 1.8d

67.3 ± 1.1a 50.3 ± 0.4a

60.9 ± 0.4b 57.9 ± 0.8b

43.7 ± 2.5c 36.4 ± 1.4c

46.3 ± 1.8c 40.2 ± 1.9c

51.4 ± 2.0d 35.6 ± 0.3c

38.4 ± 0.2e 26.6 ± 0.5d

51.7 ± 0.1a 32.3 ± 0.1a

36.9 ± 0.9b 27.9 ± 0.4b

47.1 ± 1.0c 30.8 ± 0.7a

35.4 ± 0.4b 37.2 ± 0.3c

48.3 ± 0.3c 32.8 ± 0.2a

42.1 ± 0.6d 18.3 ± 0.4d

tters in the same column indicate significant difference at p 6 0.05.

Table 2Red fraction, yellow fraction, and total carotenoid content as determined by b-carotene (lg/mL) content of NAEC by oil type.

Corn Sunflower Safflower

Red fraction (CR)a 72.0 ± 0.5a 68.4 ± 0.6b 64.4 ± 1.0b

Yellow fraction (CY)a 159.1 ± 1.8c 153.1 ± 0.4c 144.3 ± 0.5d

Total carotenoid content as b-carotene (lg/mL)

231.1 ± 2.3e 221.4 ± 1.1f 208.6 ± 6.0f

Statistical analysis was performed by the type of oil used for extraction, and dif-ferent letters indicate significant difference at p 6 0.05.

a Isochromatic families are CR: capsanthin and capsorubin; CY: zeaxanthin, b-cryptoxanthin, and b-carotene.

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3). A similar retention of antioxidant activity (82%) was reportedfor encapsulated beetroot juice processed by spray-drying (Pitaluaet al., 2010) when GA was used as an encapsulant agent.

The carotenoid content of the microencapsulated NAEC isshown in Table 3; approximately 80% of the total carotenoid con-tent was preserved, which suggests that this process is a goodmethod for conserving carotenoid content. In microencapsulatedNAEC of corn, sunflower, and safflower oils, the content of phenoliccompounds and compounds detected with Folin reagent repre-sented only 7.01%, 6.57%, and 4.64% of the total, respectively. Theseresults suggest that phenolics compounds and other compoundsdetected by Folin reagent are more susceptible to degradation dur-ing the microencapsulation process.

3.3. Water activity and moisture content of microencapsulated NAEC

The water activity and moisture content of the microcapsules ispresented in Table 3. The average water activity of the microcap-sules was between 0.15 and 0.19, and the moisture content was3.95–5.10% (dry base). No significant difference was found in wateractivity (p P 0.05). Among the parameters that determine the sta-bility of encapsulated bioactive compounds are moisture contentand water activity; therefore, it is important to understand andhave good control of these parameters during the processing andstorage of powders. Reineccius (2004) reported that when mois-ture content reaches values lower than 7%, water diffusion throughthe food matrix decreases, which reduces the effect of moisturecontent on the physical and chemical characteristics of the solidmatrix of microencapsulated oils and the accessibility of oxygento oil through the porous network. On the other hand, low valuesof water activity (p 6 0.5) have been associated with decreaseddegradation of components of the food powder. In our study, thewater that was available to carry out reactions of degradation bychemical-enzymatic mechanisms was low, and consequently thedegradation of the components of the microencapsulated NAECwas also low.

Table 3Characteristics of microencapsulated NAEC obtained from three different extracts.

Corn

Antioxidant activity (%)a 80.5 ± 3.1Red fraction (CR)b 60.3 ± 0.5Yellow fraction (CY)b 139.9 ± 0.0Total carotenoid content as b-carotene (lg/mL) 200.3 ± 0.6Moisture content (%) 4.0 ± 0.0Water activity (aw) 0.15 ± 0.0Encapsulated NAEC (%) 90.7 ± 0.5Encapsulation efficiency (%) 86.6 ± 1.4Sauter diameter (d3,2) (lm) 11.8 ± 1.5

Statistical analysis was performed by the type of oil used for extraction, and different lea Values based on the antioxidant activity with respect to the non-aqueous extracts.b Isochromatic families are CR: capsanthin and capsorubin; CY: zeaxanthin, b-cryptoxa

3.4. Morphology of microcapsules by SEM and mean particle size

Samples were examined by SEM order to determine the pres-ence of fractures, cracks, or any other possible defects that couldexpose unencapsulated NAEC, since any fracture may lead to thedegradation and oxidation of the exposed encapsulated material.In all cases, the SEM images showed the presence of semi-sphericalmicrocapsules, which showed dents and rough surfaces, but noevidence of fracture (Fig. 1).

The existence of different morphologies and surface irregulari-ties is a function of the composition of the feed, droplet size, andtemperature during the drying process (Handscomb and Kraft,2010). In some cases, shrinkage of the particle followed by anincipient expansion may induce changes in the size of particlesand broken shells (Alamilla-Beltrán et al., 2005). The typical shapeof spray-dried particles is spherical, with a mean size of10–100 mm (Fang and Bhandari, 2010). In the NAEC microcap-sules, no fractures were observed, which may be due to the lowdrying temperature as well as viscoelastic and film-formingproperties provided by the GA (Jiménez-Avalos et al., 2005;Gharsallaoui et al., 2007) that allow for better physical protectionand retention of carotenoids (Table 3). In addition, the irregularityon the surface of the microcapsules may be desirable in termsof enhanced dispersibility and rehydration of the powders(Pérez-Alonso et al., 2009).

The Sauter (d3,2) diameter for the different types of microcap-sules is shown in Table 3. The highest value of d3,2 was observedfor the microcapsules obtained with safflower oil (approximately12 lm). Jafari et al., 2007 studied emulsions of d-limonene and fishoil with Hi-Cap and WPC as wall materials and reported that par-ticle size could be related to the amount of extractable oil. Theyalso found that it is possible to have more extractable oil on thesurface of large particles than on small particles; however, in theNAEC microcapsules, no significant differences (p 6 0.05) werefound in particle size of the fraction of non-encapsulated oil. There-fore, the mean particle size is an important factor in terms of qual-ity and the possible application of the microcapsules. The spanvalues for the microcapsules of NAEC were 2.47 ± 0.2, 2.21 ± 0.3,and 1.73 ± 0.2 using corn, sunflower, and safflower oils for extrac-tion, respectively. In all cases, the low span values indicated amonodisperse distribution of mean size particle (Jiménez-Alvaradoet al., 2009).

Although microcapsules made with safflower oil extract had atendency towards monodispersity (Fig. 2), they had the highestmean particle size, which may be due to the fact that this oil mod-ified the characteristics of the surface of particles undergoing dry-ing as well as size and viscosity of the emulsion. Tcholakova et al.(2011) found that the Sauter diameter (d3,2) increased in emulsionsas the viscosity of the oily phase increased (hexadecane, mineraloils, and silicone oils, which had different values of viscosity).

Sunflower Safflower

a 80.0 ± 3.1a 76.5 ± 3.1b

c 58.8 ± 0.6c 53.3 ± 0.2d

4e 126.9 ± 1.1f 122.4 ± 0.9f

g 185.8 ± 0.5h 175.8 ± 0.7i

5j 5.0 ± 0.1k 3.9 ± 0.03j

1l 0.18 ± 0.01l 0.19 ± 0.01l

m 90.4 ± 0.6m 91.6 ± 0.6m

n 83.9 ± 1.5n 84.2 ± 1.0n

o 11.1 ± 1.4o 12.7 ± 0.5o

tters indicate a significant difference at p 6 0.05.

nthin, and b-carotene expressed as lg/mL of extract.

Fig. 1. Scanning electron microscopy (SEM) micrographs of the microcapsules obtained from extracts using (a) corn oil, (b) sunflower oil, and (c) safflower oil.

34 A.Y. Guadarrama-Lezama et al. / Journal of Food Engineering 112 (2012) 29–37

The viscosity of the refined oils, which constitute the oil phase ofemulsions, was found to be 51.44 (25 �C), 48.98 (25 �C), and 52(30 �C) cP for corn, sunflower, and safflower oils, respectively(Abromovic and Klofutar, 1998; Khtoon and Krishna, 1998; Rogerset al., 2011).

Fig. 2. Distribution of particle size for the microcapsules obtained from extractsusing corn oil, sunflower oil, and safflower oil.

3.5. Encapsulated NAEC and encapsulation efficiency

Two wall materials were chosen based on a consideration ofimportant characteristics, such as solubility and the capacity toprotect against oxidation. In order to select the wall material formicroencapsulation, the optimal mixture of GA and MD was firstlydetermined, and different ratios of core:wall material were tested.It has been reported that when the concentration of oil in an emul-sion preparation is 5%, better homogenization and high encapsu-lated oil were are obtained (Martins and Kieckbusch, 2009).

Emulsions and microcapsules were prepared in 1:1, 2:1, and 1:2(GA–MD) ratios at a final concentration of 20% solids and 5% oilyphase. The results showed that a ratio of 1:2 (GA–MD) preserved90% of the antioxidant activity of the extract, while a ratio of2:1(GA–MD) only preserved approximately 77% of the activity.However, the uncapsulated NAEC at a ratio of 1:2 was 49.3% andratio of 2:1 was 17%, which is unfavorable in terms of NAECconservation, since greater exposure increases the susceptibility

A.Y. Guadarrama-Lezama et al. / Journal of Food Engineering 112 (2012) 29–37 35

to degradation. At a ratio of 1:1 (GA–MD), 80% of the antioxidantactivity was preserved, while approximately 86% of the extractwas encapsulated and therefore less prone to degradation by envi-ronmental factors. Therefore, this ratio of wall materials was usedto encapsulate the extracts. Spray-drying is generally performed at180–220 �C, and 60–80 �C is used for inlet and outlet air tempera-tures, respectively (Sabliov and Astete, 2008; Tonon et al., 2011).Based on this range of temperatures, we performed the microen-capsulation of NAEC at two different temperatures. Using inlet/outlet drying air temperatures of 170/90 �C, respectively, the pow-der recovery efficiency was very low, and a high concentration ofencrusted product on the wall of the drying camera occurred. Thus,to perform this work, the lower temperatures (160/70 �C) were se-lected. Atomizer pressures from 0.2 to 1 kg/cm2 were also tested,and we found that when the nozzle pressure was 1 kg/cm2, thedrops were projected on the walls of the drying chamber with alow recovery of powders. In contrast, when 0.4 kg/cm2 of pressurewas used, higher yields were obtained in the recovery of powders.

Suitable antioxidant activities were obtained when a blend ofGA and MD 20DE was used at a 1:1 ratio according to the prepara-tion in Section 2.2.5. The NAEC (core) can be delivered by differenttransport mechanisms through the layers of the encapsulatingmaterials that provide the structure for the capsules as well asby aqueous solubilization of wall materials. The product obtainedhas high antioxidant activity and carotenoids, so it could be usedin nutraceutical foods and possibly as a natural antimicrobial(Careaga et al., 2003).

The non-extractable fraction of NAEC, which was evaluated as apercentage of encapsulated NAEC, was between 90% and 91% formicroencapsulates of the three different non-aqueous extracts(corn, sunflower, and safflower), and approximately 9–10% forthe extractable fraction of NAEC (Table 3). No significant differ-ences were found between the values of EE among the different ex-tracts (p P 0.05). The amount of extractable oil depends on theemulsion process, drying air temperatures, and physicochemicalcharacteristics of the wall material, which were kept constant. Itis possible that the content of saturated fatty acids induced differ-ent arrangements among the components of the wall materialsduring microcapsule development. Another factor that affects thecontent of non-encapsulated oil is the porosity of the wall materialand the method of extraction used. Drusch and Berg (2008) foundthat the amount of non-encapsulated oil was slightly higher formicroencapsulation at drying temperatures (inlet/outlet) of 210/90 �C compared to 160/60 �C. The EE was 83–86% for the threedifferent encapsulates in relation to total carotenoid content (Table3). The EE and extractable portion of NAEC and NAEC microcap-sules was based on total carotenoid content (expressed as b-caro-tene) as the target chemical component.

Rocha et al. (2012) found that the EE of lycopene microencapsu-lation was 21–29% using modified starch as the wall material.Rodriguez-Huezo et al. (2004) reported that the microencapsula-tion efficiency was between 25.6% and 87.5% for emulsions con-taining carotenoids using GA, gellan gum, and MD as wallmaterials.

3.6. Stability tests for microencapsulates

The preservation of the antioxidant activity and water activityof microencapsulated NAEC was evaluated after 60 d of storage,which is the average time for consumption of a food powder, at20 ± 5 �C (Davoodi et al., 2007). As shown in Table 4, the microcap-sules retained approximately 72%, 68%, and 61% of the initial anti-oxidant activity for corn, sunflower, and safflower extracts,respectively, after 60 d of storage. These results only representeda loss of 8.5%, 12%, and 15% of the antioxidant activity, respectively,compared to the original microencapsulated NAEC that was

evaluated at time zero. The yellow and red fractions as well as totalcarotenoid content are shown in Table 4. Total carotenoid contentin the microencapsulated NAEC decreased by 22.1%, 22.7%, and27.6% for NAEC prepared with corn, sunflower, and safflower oils,respectively, during the storage period. The carotenoids frommicrocapsules of NAEC prepared with corn oil had the highest anti-oxidant activity, which may be due to different fatty acid composi-tion of the oils. Corn oil has a higher proportion (12.2%) ofsaturated fatty acids compared to sunflower (10%) and safflower(7.42%) oils, according to Mexican Standard References (NMX-F-030-SCFI-2005; NMX-F-265-SCFI-2005; NMX-161-SCFI-2007),which makes it less susceptible to degradation by oxidation. Theoxidation of fatty acids is a chain reaction due to various factors,such as temperature, light, and the presence of metals. Once thisreaction is initiated in the fatty acids, it continues in the carote-noids (co-oxidation) (Takahashi et al., 2003). Saturated fatty acidsare more stable than polyunsaturated and monounsaturated fattyacids, suggesting that carotenoids are oxidated more rapidly bypolyunsaturated oils than by monounsaturated oils, and much lessrapidly by saturated fatty acids. Therefore, the only way by whichcarotenoids can undergo greater oxidation in oil containing moresaturated fatty acids is if the saturated oils were oxidated beforecontacting the carotenoids (Omara-Alwala et al., 1985; Bezbradicaet al., 2005; Sachindra and Mahendrakar, 2005). Changes in antiox-idant activity and total carotenoid content in the stored microcap-sules could also be related to degradation reactions of lipids andcarotenoids by complex mechanisms of co-oxidation (Takahashiet al., 2003) or to the presence of MD (D-glucose) and GA (thathas a protein portion), which may trigger the Maillard reaction thatusually occurs during food processing and storage (Pitalua et al.,2010).

Corn oil has good oxidative stability, which is partially attrib-uted to the nonrandom distribution of fatty acids on triglycerides.It has been determined that 98% of the fatty acids esterified in thesn-2 position of corn oil triglycerides are unsaturated, leaving theouter sn-1 and sn-3 positions with possibilities of binding satu-rated fatty acids and the unsaturated acids that may still be presentin the oil. Therefore, since the outer positions of the triglyceridesare more reactive, the polyunsaturated fatty acids in the sn-2 posi-tion present a certain degree of protection from oxidation (O’Brien,2004).

The extractable fraction of the oil phase, which has greaterexposure to oxygen, was more susceptible to the oxidation pro-cesses than the encapsulated fraction (Shimada et al., 1991;Velasco et al., 2000) which is less exposed to oxygen, in the NAECmicrocapsules prepared with sunflower and safflower oils. Theopposite was observed for microcapsules prepared with corn oil,even though a similar percentage of non-encapsulated oil waspresent for the three types of NAEC microcapsules. This observa-tion could be due to the above mentioned lower proportion ofunsaturated fatty acids present in corn oil compared with sun-flower and safflower oils.

The loss of antioxidant activity and total carotenoid content ofthe microencapsulates may be directly related to the amount ofextractable or non-encapsulated oil containing carotenoids in themicrocapsules, which is exposed to oxygen and causes oxidationof carotenoids. In addition, the presence of open pores in the wallof microcapsules allows accessibility of oxygen to NAEC structures.Márquez-Ruiz et al. (2003) reported that the extractable oil frac-tion in matrices containing an oily phase is affected by numerousvariables, but in some cases, the extractable oil was more proneto oxidation than the non-extractable fraction.

The delivery and controlled release of carotenoids from micro-capsules are decisive in understanding the effects of the activeagent for a particular application and impact their availability.The release of bioactives from capsules is affected by the chemical

Table 4Characteristics of NAEC microcapsules after storage for 60 d at 20 ± 5 �C.

Corn Sunflower Safflower

Antioxidant activity (%)a 72.0 ± 0.8a 68.1 ± 2.2a 61.3 ± 3.4b

Red fraction (CR)b 59.2 ± 0.1c 54.3 ± 0.03c 51.3 ± 0.04c

Yellow fraction (CY)b 96.8 ± 1.2d 89.3 ± 0.5e 75.9 ± 0.5f

Total carotenoid content asb-carotene (lg/mL)

156.0 ± 3.9g 143.6 ± 0.1h 127.2 ± 1.0i

Water activity (aw) 0.17 ± 0.01l 0.18 ± 0.01l 0.15 ± 0.0l

Moisture content (%) 3.06 ± 0.3m 5.50 ± 0.2n 5.02 ± 0.07n

Statistical analysis was performed by the type of oil used for extraction, and dif-ferent letters indicate a significant difference at p 6 0.05.

a Values based on the antioxidant activity with respect to the non-aqueousextracts.

b Isochromatic families are CR: capsanthin and capsorubin; CY: zeaxanthin,b-cryptoxanthin, and b-carotene expressed as lg/mL of extract.

36 A.Y. Guadarrama-Lezama et al. / Journal of Food Engineering 112 (2012) 29–37

structure of the wall materials and active agent, concentration ofencapsulated antioxidant, environmental conditions (temperature,pH, and release media), and particle size and its morphology (Leeand Ying, 2008). Active compounds with antioxidant activity, suchas the non-aqueous extracts of Capsicum, may be of potential appli-cation in the food industry; however, their use depends on the re-lease mechanism. One of the methods for achieving controlledrelease in foods is microencapsulation, which has been reportedto release the active agent by diffusion, biodegradation, swelling,or osmotic pressure (Pothakamury and Barbosa-Cánovas, 1995;Sabliov and Astete, 2008). The release of microencapsulated NAECcan occur by a diffusion process through the polymeric material aswell as solubilization of wall material; however, application of thistechnology would depend on the specific use or consumption ofthe microcapsules (Lee and Ying, 2008).

4. Conclusions

In this study, we obtained non-aqueous extracts of Capsicumwith high antioxidant activity by using edible vegetable oils asextraction media, thus avoiding the use of volatile solvents thatare potentially harmful to the environment. Corn oil provided thehighest yields during the extraction, and the microcapsules ob-tained with this oil were the most stable. The encapsulation ofnon-aqueous extracts by spray-drying allowed for the protectionof active agents of the extracts against oxidative and deteriorationprocesses. Approximately 80% of the antioxidant activity of thenon-aqueous extracts was preserved in the microencapsulates.The microcapsules did not contain fractures, and this finding mayhave contributed to the protective action against oxidation. Themicrocapsules obtained could be included as functional ingredi-ents in a diverse range of food products and may have utility asa possible natural antimicrobial agent.

Acknowledgements

The authors thank the financial support for this work from theNational Polytechnic Institute (IPN-Mexico) through the ProjectsSIP 20121026, SIP 20121754, and the PIFI Program as well as fromthe Institute of Science and Technology of Mexico Citys Govern-ment (ICYTDF) through the Project PICS08-15. Author Guadarrama-Lezama received a study grant from the Mexican National Councilfor Science and Technology (CONACYT).

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