5. desai, park - 2005 - recent developments in microencapsulation of food ingredients.pdf

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This article was downloaded by: [b-on: Biblioteca do conhecimento onlineUP]On: 24 April 2012, At: 09:04Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK

Drying Technology: An

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Recent Developments inMicroencapsulation of Food

IngredientsKashappa Goud H. Desai

a& Hyun Jin Park

a

aGraduate School of Biotechnology, Korea

University, Sungbuk-ku, Seoul, South Korea

Available online: 06 Feb 2007

To cite this article:Kashappa Goud H. Desai & Hyun Jin Park (2005): Recent

Developments in Microencapsulation of Food Ingredients, Drying Technology: An

International Journal, 23:7, 1361-1394

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Recent Developments in Microencapsulation ofFood Ingredients

Kashappa Goud H. Desai and Hyun Jin Park*

Graduate School of Biotechnology, Korea University, Sungbuk-ku,Seoul, South Korea

Abstract: Microencapsulation involves the incorporation of food ingredients,enzymes, cells, or other materials in small capsules. Microcapsules offer food pro-cessors a means with which to protect sensitive food components, ensure againstnutritional loss, utilize otherwise sensitive ingredients, incorporate unusual ortime-release mechanisms into the formulation, mask or preserve flavors and aro-mas, and transform liquids into easily handled solid ingredients. Various techni-

ques are employed to form microcapsules, including spray drying, spray chillingor spray cooling, extrusion coating, fluidized-bed coating, liposome entrapment,coacervation, inclusion complexation, centrifugal extrusion, and rotationalsuspension separation. Recent developments in each of these techniques arediscussed in this review. Controlled release of food ingredients at the right placeand the right time is a key functionality that can be provided by microencapsulation.A timely and targeted release improves the effectiveness of food additives, broadensthe application range of food ingredients, and ensures optimal dosage, therebyimproving the cost effectiveness for the food manufacturer. Reactive, sensitive, orvolatile additives (vitamins, cultures, flavors, etc.) can be turned into stable ingre-

dients through microencapsulation. With carefully fine-tuned controlled-releaseproperties, microencapsulation is no longer just an added-value technique, but thesource of totally new ingredients with matchless properties.

Keywords: Microencapsulation; Food ingredients; Controlled release; Spraydrying; Microcapsules

INTRODUCTION

Microencapsulation is defined as a technology of packaging solids,liquids, or gaseous materials in miniature, sealed capsules that can release

Correspondence: Hyun Jin Park, Graduate School of Biotechnology, KoreaUniversity, 1, 5-Ka, Anam-Dong, Sungbuk-ku, Seoul 136701, South Korea;Tel.: 82-2-3290-3450; Fax: 82-2-953-5892; E-mail: [email protected]

Drying Technology, 23: 13611394, 2005Copyright Q 2005 Taylor & Francis, Inc.ISSN: 0737-3937 print/1532-2300 onlineDOI: 10.1081/DRT-200063478

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their contents at controlled rates under specific conditions.[16] Themicroencapsulation technology has been used by the food industry formore than 60 years. In a broad sense, encapsulation technology in foodprocessing includes the coating of minute particles of ingredients (e.g.,acidulants, fats, and flavors) as well as whole ingredients (e.g., raisins,nuts, and confectionary products), which may be accomplished by micro-encapsulation and macro-coating techniques, respectively.[7] Morespecifically, the microcapsule has the ability to preserve a substance inthe finely divided state and to release it as occasion demands.[8] Thesemicrocapsules may range from submicrometer to several millimeters insize and have a multitude of different shapes, depending on the materialsand methods used to prepare them. The food industry applies micro-encapsulation process for a variety of reasons: (1) encapsulation=entrapment can protect the core material from degradation by reducingits reactivity to its outside environment (e.g., heat, moisture, air, andlight), (2) evaporation or transfer rate of the core material to the outsideenvironment is decreased=retarded, (3) the physical characteristics of theoriginal material can be modified and made easier to handle, (4) the pro-duct can be tailor to either release slowly over time or at a certain point(i.e., to control the release of the core material to achieve the propertydelay until the right stimulus), (5) the flavor of the core material canbe masked, (6) the core material can be diluted when only very smallamounts are required, yet still achieve a uniform dispersion in the hostmaterial, and (7) it can be employed to separate components within amixture that would otherwise react with one another.[914]

Various properties of microcapsules that may be changed to suit spe-cific ingredient applications include composition, mechanism of release,particle size, final physical form, and cost. The architecture of microcap-sules is generally divided into several arbitrary and overlapping classifica-

tions (Fig. 1). One such classification is known matrix encapsulation.This is the simplest structure, in which a sphere is surrounded by a wallor membrane of uniform thickness resembling that of a hens egg. In thisdesign, the core material is buried to varying depths inside the shell. Thismicrocapsule has been termed a single-particle structure (Fig. 1A). It isalso possible to design microcapsules that have several distinct coreswithin the same microcapsule or, more commonly, number numerouscore particles embedded in a continuous matrix of wall material. Thistype of design is termed the aggregate structure (Fig. 1B).

In order to improve the properties of food ingredients, immobiliza-tion of food ingredients onto a suitable polymer or addition of antimicro-bial agents are common practices in the food industres.[1517] Forexample, an important bacteria used in the food industry, lactic acid bac-teria, was first immobilized in 1975 on Berl saddles and Lactobacilluslactis was encapsulated in alginate gel beads years later.[18] Seiss andDavis suggested that immobilized lactic acid bacteria could be used to

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continuously produce yogurt.[19] However, the alginate gel beads leakedlarge quantities of cells.

The use of microencapsulated food ingredients allows food ingredi-ents to be carefully tailored to the specific release site through the choiceand microencapsulation variables, specifically, the method and foodingredients-polymer ratio.[7] The total amount of ingestion and thekinetics of release are variables that can be manipulated to achieve thedesired result.[7,9,14] Using innovative microencapsulation technologies,and varying the copolymer ratio, molecular weight of the polymer, etc.,microcapsules can be developed into an optimal food ingredient device. [7]

Microcapsule-based systems increases the life span of food ingredientsand control the release of food ingredients.

Various properties of microcapsules that may be changed to suitspecific ingredient applications include composition, mechanism ofrelease, particle size, final physical form, and cost. Before considering

the properties desired in encapsulated products, the purpose of encapsu-lation must be clear. In designing the encapsulation process, the followingquestions are taken into consideration:

1. What functionality should the encapsulated ingredients provide thefinal product?

2. What kind of coating material should be selected?3. What processing conditions must the encapsulated ingredient survive

before releasing its content?

4. What is optimal concentration of the active ingredient in themicrocapsule?

5. By what mechanism the ingredient be released from themicrocapsules?

6. What are the particle size, density, and stability requirements for theencapsulated ingredient?

7. What are the cost constraints of the encapsulated ingredient?

Figure 1. Schematic diagram of two representative types of microcapsules.

Microencapsulation of Food Ingredients 1363

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Controlled release may be defined as a method by which one or moreactive agents or ingredients are made available at a desired site and timeat a specific rate. With the emergence of controlled-release technology, someheat-, temperature-, or pH-sensitive additives can be used very convenientlyin food systems. Such additives are introduced into the food system mostlyin the form of microcapsules. The additive present in the microcapsule isreleased under the influence of a specific stimulus at a specified stage. Forexample, flavors and nutrients may be released upon consumption, whereassweeteners that are susceptible to heat may be released toward the end ofbaking, thus preventing undesirable caramelization in the baked pro-duct.[2030] Although quite a number of reviews are published on the micro-encapsulation of food ingredients, we have made an attempt here to updatethe recent developments in the microencapsulation of food ingredients.

MICROENCAPSULATION TECHNIQUES

Encapsulation of food ingredients into coating materials can be achievedby several methods. The selection of the microencapsulation process isgoverned by the properties (physical and chemical) of core and coatingmaterials and the intended application of food ingredients. However,the microencapsulation processes that are used to encapsulate food ingre-dients are given in Table 1, which outlines various methods used for thepreparation of microencapsulated food systems. Sophisticated shell mate-rials and technologies have been developed and an extremely wide varietyof functionalities can now be achieved through microencapsulation. Anykind of trigger can be used to prompt the release of the encapsulatedingredient, such as pH change (enteric and anti-enteric coating), mechan-ical stress, temperature, enzymatic activity, time, osmotic force, etc. How-ever, cost considerations in the food industry are much more stringent

than in, for instance, the pharmaceutical or cosmetic industries. Theselection of microencapsulation method and coating materials are inter-dependent. Based on the coating material or method applied, the appro-priate method or coating material is selected. Coating materials, whichare basically film-forming materials, can be selected from a wide varietyof natural or synthetic polymers, depending on the material to be coatedand characteristics desired in the final microcapsules.

The composition of the coating material is the main determinant ofthe functional properties of the microcapsule and of how it may be used

to improve the performance of a particular ingredient. An ideal coatingmaterial should exhibit the following characteristics:

1. Good rheological properties at high concentration and easy work-ability during encapsulation.

2. The ability to disperse or emulsify the active material and stabilize theemulsion produced.

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Table 1. Various microencapsulation techniques and the processes involved ineach technique

No Microencapsulation technique Major steps in encapsulation

1 Spray-drying a. Preparation of the dispersionb. Homogenization of the dispersionc. Atomization of the infeed dispersiond. Dehydration of the atomized particles

2 Spray-cooling a. Preparation of the dispersionb. Homogenization of the dispersionc. Atomization of the infeed dispersion

3 Spray-chilling a. Preparation of the dispersionb. Homogenization of the dispersionc. Atomization of the infeed dispersion

4 Fluidized-bed coating a. Preparation of coating solutionb. Fluidization of core particles.c. Coating of core particles

5 Extrusion a. Preparation of molten coating solutionb. Dispersion of core into molten

polymerc. Cooling or passing of core-coat

mixture through dehydrating liquid6 Centrifugal extrusion a. Preparation of core solution

b. Preparation of coating materialsolution

c. Co-extrusion of core and coatsolution through nozzles

7 Lyophilization a. Mixing of core in a coating solutionb. Freeze-drying of the mixture

8 Coacervation a. Formation of a three-immisciblechemical phases

b. Deposition of the coatingc. Solidification of the coating

9 Centrifugal suspensionseparation

a. Mixing of core in a coating materialb. Pour the mixture over a rotating disc

to obtain encapsulated tiny particlesc. Drying

10 Cocrystallization a. Preparation of supersaturatedsucrose solution

b. Adding of core into supersaturatedsolution

c. Emission of substantial heat aftersolution reaches the sucrosecrystallization temperature

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3. Nonreactivity with the material to be encapsulated both during pro-cessing and on prolonged storage.

4. The ability to seal and hold the active material within its structureduring processing or storage.

5. The ability to completely release the solvent or other materials usedduring the process of encapsulation under drying or other desolventi-zation conditions.

6. The ability to provide maximum protection to the active materialagainst environmental conditions (e.g., oxygen, heat, light, humidity).

7. Solubility in solvents acceptable in the food industry (e.g., water,ethanol).

8. Chemical nonreactivity with the active core materials.9. Inexpensive, food-grade status.

Because no single coating material can meet all of the criteria listedabove, in practice either coating materials are employed in combinationsor modifiers such as oxygen scavengers, antioxidants, chelating agents,and surfactants are added. Some commonly used biocompatible andfood-grade coating materials are listed in Table 2. However, chemicalmodifications of the existing coating materials to manipulate theirproperties are also being considered. Those modified coating materialsexhibit better physical and mechanical properties when compared to indi-vidual coating materials.

Spray-Drying

Spray-drying encapsulation has been used in the food industry since the

late 1950s to provide flavor oils with some protection against degrada-tion=oxidation and to convert liquids to powders. Spray-drying is themost widely used microencapsulation technique in the food industryand is typically used for the preparation of dry, stable food additivesand flavors. The process is economical; flexible, in that it offers substan-tial variation in microencapsulation matrix; adaptable to commonly usedprocessing equipment; and produces particles of good quality. In fact,

Table 1. (Continued)

No Microencapsulation technique Major steps in encapsulation

11 Liposome entrapment a. Microfluidizationb. Ultrasonicationc. Reverse-phase evaporation

12 Inclusion complexation Preparation of complexes by mixing orgrinding or spray-drying

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spray-drying production costs are lower than those associated with mostother methods of encapsulation. One limitation of the spray-drying tech-nology is the limited number of shell materials available. Since almost allspray-drying processes in the food industry are carried out from aqueousfeed formulations, the shell material must be soluble in water at anacceptable level. Typical shell materials include gum acacia, maltodex-

trins, hydrophobically modified starch, and mixtures thereof. Other poly-saccharides (alginate, carboxymethylcellulose, guar gum) and proteins(whey proteins, soy proteins, sodium caseinate) can be used as the wallmaterial in spray-drying, but their usage becomes very tedious andexpensive because of their low solubility in water: the amount of waterin the feed to be evaporated is much larger due to the lower dry mattercontent and the amount of active ingredient in the feed must be reducedaccordingly. In this method, the material for encapsulation is homo-genized with the carrier material at a different ratio. The mixture is then

fed into a spray dryer and atomized with a nozzle or spinning wheel.Water is evaporated by the hot air contacting the atomized material.The microcapsules are then collected after they fall to the bottom ofthe drier.[31]

Rosenberg and Sheu demonstrated the use of whey protein isolate asa wall material for encapsulation of volatiles.[32] They encapsulated ethylbutyrate and ethyl caprylate in whey protein isolate and 1:1 mixture of

Table 2. Coating materials for microencapsulation of functional food additives

Category Coating materialsWidely used

methods References

Carbohydrate Starch,maltodextrins,chitosan,corn syrup solids,dextran, modifiedstarch, cyclodextrins

Spray- andfreeze-drying,extrusion,coacervation,inclusioncomplexation

2024

Cellulose Carboxymethylcellulose,

methyl cellulose,ethylcellulose,

celluloseacetate-phthalate,celluloseacetate-butylate-phthalate

Coacervation,

spray-drying,and edible films

2526

Gum Gum acacia, agar, sodiumalginate, carrageenan

Spray-drying, syringemethod (gel beads)

27

Lipids Wax, paraffin, beeswax,diacylglyerols, oils, fats

Emulsion, liposomes,film formation

2829

Protein Gluten, casein, gelatin,

albumin, peptides

Emulsion, spray-drying 30


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whey protein isolate and lactose. Retention of volatiles was significantlyaffected by wall solids concentration (1030%, w=w), initial ester load(1075%, w=w, of wall solids), and by ester and wall type. Ester retentionin whey protein isolate=lactose was higher than in whey protein isolate.Spray-drying is a food manufacturerfriendly technique because it allowsthe food processor to manipulate the preparation process to improve thequality of the final product. Recently, Shiga et al. prepared flavor-inclusion powder by a spray-drying technique using the combined encap-sulation method of inclusion by b-cyclodextrin and emulsified by gumarabic where d-limonene and ethyl n-hexanoate were used as modelflavors.[33] The effective film-forming property and inclusion complexwere achieved by applying high pressure to the mixture of flavors andb-cyclodextrin slurry using a microfluidizer. It is reported that flavorretention during spray-drying increased due to blending of gum arabicand b-cyclodextrin in the feed liquid. The release rate of flavors wasmanipulated by the blending of maltodextrin in the feed liquid. In orderto evaluate the release kinetics of flavors, the release data were fitted toAvramis equation (Eq. 1).

R expktn 1

where R is the retention of flavors during release, t is time, n is a para-meter representing the release mechanism, and k is the release rate con-stant. Eq. (1) was originally developed the crystal growth of polymers,and has been recently used to represent the time-dependent proteininactivation in amorphous sugar matrices.[34] In Eq. (1), n 1 representsthe first-order reaction, and n 0.54 represents the diffusion-limitingreaction kinetics.[35] Taking a logarithm of both sides of Eq. (1) twiceyields Eq. (2):

lnln R n ln kn ln t 2

From Eq. (2) one can find the parameternas a slope by plotting ln(lnR) vs. lnt, and the release rate constantkfrom the interception at lnt 0.

It is important to protect the flavor loss during drying, becausehigh-temperature air is commonly used in spray-drying. Generally, theretention of flavor in microcapsules is manipulated by varying thespray-drying conditions and compositions of wall material. Recently,Liu et al. adopted new technique where they used emulsified liquid flavor

for spray-drying.[36] Nearly 100% of d-limonene was retained duringspray-drying, independent of the composition of the feed liquid. How-ever, the stability of emulsion droplets markedly affected the retentionof flavors. d-Limonene emulsion was quite stable independent of theemulsifier, while the emulsion of ethyl butyrate was unstable with gumarabic as the emulsifier. The use of a mixture of gum arabic and solublesoybean polysaccharide as the emulsifier improved oiliness, and adjusting

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density of ethyl butyrate and adding gelatin increased the retention ofethyl butyrate during spray-drying.

In recent years, new wall materials for use in spray-drying microen-capsulation have not really emerged. A few exceptions are noteworthy,though. The investigations of other natural gums and their emulsificationand shell properties have been reported. Mesquite gum, for instance, hasbeen shown to give a better stability of the o=w emulsions and higherencapsulation efficiency compared to gum acacia.[37,38] Augustin et al.proposed the use of Maillard reaction products (MRPs) obtained bythe reaction at high temperature between protein and carbohydrate toencapsulate oxidation-sensitive nutrients such as fish oils.[39] The MRPsare known to exhibit antioxidant properties and form a stable and robustshell around the oil phase. The stability of the oil against oxidation wasgreatly improved compared to nonencapsulated spray-dried samples inordinary shell material. More interesting is the recent development ofcomplex shell formulations for spray-drying encapsulation. For instance,aqueous two-phase systems (ATPSs), which result from the phase separ-ation of a mixture of soluble polymers in a common solvent due to thelow entropy of mixing (DSmix) of polymer mixtures, can be used to designdouble-encapsulated ingredients in a single spray-drying step. Millqvist-Fureby et al. encapsulatedEnterococcus fciumin a mixture of polyvinyl-pyrrolidone (PVP) and dextran.[40] While proteins exhibit partitioningbetween the two phases, whole cells tend to concentrate in one of thepolymer phases, which make them ideal candidates for ATPS spray-drying.The structure of the microcapsule, whether PVP is the outer layer anddextran the inner core or vice versa, can be controlled by adjusting the ratioand concentration of the two polymers. Encapsulated E. fcium in spray-dried ATPS showed a survival rate of up to 45% after 4 weeks at roomtemperature. Another example is the preparation and spray-drying of mul-

tiple emulsions, which results a in a double-layered microcapsule, providingbetter protection to sensitive materials such as oxidation-probe flavor oils.Edris and Bergmtahl have encapsulated orange oil by first preparing a tripleemulsion o=w=o=w and then evaporating the outer continuous aqueousphase, which contains sodium caseinate and lactose as shell material, byspray-drying.[41] The process leads to a dry free-flowing powder constitutingof a double o=w=o, in which the inner orange oil phase is dispersed in anaqueous phase, which is itself dispersed in an oil phase encapsulated insodium caseinate and lactose. This double emulsion process is not practi-

cally more complex than a typical spray-drying process that requires anemulsion step anyway. However, preparing a second emulsion implies adilution of the flavor oil, and the much lower payload in the microcapsule(510%) is a drawback compared to typical spray-dried flavor oils, whichhave payloads of around 2025%. The unique protection and delayed-release properties obtained with two layers might compensate for the lowerpayload, but this has still to be demonstrated.


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Chitosan is a hydrophilic, biocompatible, and biodegradable, poly-saccharide of low toxicity. In recent years, it has been used for develop-ment of oral controlled drug delivery systems. It is also a well-knowndietary food additive. Therefore, our research team demonstrated thecross-linked chitosan as a wall material for the encapsulation of vitaminC by a spray-drying technique. Vitamin C, a representative water-solublevitamin, has a variety of biological, pharmaceutical, and dermatologicalfunctions. Vitamin C is widely used in various types of foods as a vitaminsupplement and as an antioxidant. Hence, in previous studies, sustained-release carriers of vitamin C have been prepared by using cross-linkedchitosan as a wall material by spray-drying technique. [4244] The processof the preparation of vitamin Cencapsulated chitosan microcapsules isshown in Fig. 2. Chitosan was cross-linked with nontoxic cross-linkingagent, i.e., tripolyphosphate. Vitamin Cencapsulated chitosan micro-spheres of different size, surface morphology, loading efficiency, and zetapotential with controlled-release property could be obtained by varyingthe manufacturing parameters (inlet temperature, flow rate) and usingthe different molecular weight and concentration of chitosan. VitaminCencapsulated chitosan microcapsules were spherical in shape with asmooth surface as observed by scanning electron microscopy (Fig. 3).Microencapsulation of vitamin C improves and broadens its applicationsin the food industry.

Figure 2. Procedure of preparation of vitamin Cencapsulated chitosanmicrospheres by spray-drying.

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Numerous materials have been used as flavor-encapsulating agentsusing a spray-drying technique. These include proteins, gums, and modi-fied starches.[45] An area of research of increasing interest is the develop-ment of alternative and inexpensive polymers that may be considerednatural, like gum arabic, and that could encapsulate flavors with the

same efficiency as gum arabic.[46] Mesquite gum has been reported as avery good encapsulating agent.[47,48] Beristain and Vernon-Carter notedthat a blend of 60% gum arabic and 40% mesquite gum encapsulated93.5% of orange peel oil.[49] More recently, Beristain et al. reported thata mixture consisting of 40% mesquite gum and 60% maltodextrins wasable to encapsulate 84.6% of the starting oil.[50] Cardamom-based oilmicrocapsules were successfully produced by spray-drying using mesquitegum.[38] The stability against drop coalescence of the emulsions was elev-ated for all the gum:oil ratios studied. High flavor retention (83.6%) was

attained during microencapsulation by spray-drying when a proportionof 4:1 gum:oil was used. This confirmed the interesting emulsifyingproperties and good flavor-encapsulation ability that qualify mesquitegum as an important alternative encapsulating medium. The microcap-sules can be readily used as a food ingredient.

Recent developments have been in the use of new carrier materialsand a newly designed spray dryer. Colloides Naturels and TIC Gums

Figure 3. Scanning electronic microscopic picture of the vitamin C-encapsulatedmicrocapsule.


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have developed new combinations of gum arabic starches to increasethe retention of volatiles and shelf life of microcapsules.[51,52] Risch andReineccius enhanced the retention of orange oil and decreased oxidationby using gum arabic.[53] Bhandari et al. showed that a new type of dryercalled the Leaflish spray dryer, which uses a high air velocity with a tem-perature of 300 to 400C, was effective for encapsulating citral and linalylacetate without degradation.[54] A disadvantage is that a separateagglomeration step is required to prevent separation or to render theobtained powder soluble. A chief advantage is that this technique canbe used for heat-labile materials. Recently, studies on the modificationof spray-drying chamber configurations and atomization along applica-tions of computational fluid dynamic model have been reported tobroaden the applications range of spray-drying methods.[5560]

Spray-Chilling or Spray-Cooling

In spray-chilling and spray-cooling, the core and wall mixtures areatomized into the cooled or chilled air, which causes the wall to solidifyaround the core. Unlike spray-drying, spray-chilling or spray-cooling

does not involve evaporation of water. In spray-cooling, the coatingmaterial is typically some form of vegetable oil or its derivatives. How-ever, a wide range of other encapsulating materials may be employed.These include fat and stearin with melting points of 45122C, as wellas hard mono- and diacylglycerols with melting points of 4565C.[31]

In spray-chilling, the coating material is typically a fractionated or hydro-genated vegetable oil with a melting point in the range of 3242C.[61] Inspray-chilling, there is no mass transfer (i.e., evaporation from the ato-mized droplets); therefore these solidify into almost perfect spheres to

give free-flowing powders. Atomization gives an enormous surface areaand an immediate as well as intimate mixing of these droplets with thecooling medium. Microcapsules prepared by spray-chilling and spray-cooling are insoluble in water due to the lipid coating. Consequently,these techniques tend to be utilized for encapsulating water-soluble corematerials such as minerals, water-soluble vitamins, enzymes, acidulants,and some flavors.[62]

Fluidized-Bed Coating

Originally developed as a pharmaceutical technique, fluidized-bed coat-ing is now increasingly being applied in the food industry to fine-tunethe effect of functional ingredients and additives. The main benefits ofsuch miniature packages, called microcapsules, include increased shelflife, taste masking, ease of handling, controlled release, and improvedaesthetics, taste, and color. Fluidized-bed coating increasingly supplies

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the food industry with a wide variety of encapsulated versions of foodingredients and additives.[63] Compared to pharmaceutical fluidized-bedcoating, food industry fluidized-bed coating is more obliged to cutproduction costs and, therefore, should adopt a somewhat differentapproach to this rather expensive technology. Solid particles are sus-pended in a temperature and humidity-controlled chamber of high-velocity air where the coating material is atomized.[64,65] Typical foodprocessing applications of fluidization include freezing and cooling, dry-ing, puffing, freeze-drying, spray-drying, agglomeration and granulation,classification, and blanching and cooking.[66] Great variations in avail-able wall materials exist. Cellulose derivatives, dextrins, emulsifiers,lipids, protein derivatives, and starch derivatives are examples of typicalcoating systems, and they may be used in a molten state or dissolved in anevaporable solvent. This technique is applicable for hot-melt coatingssuch as hydrogenated vegetable oil, stearines, fatty acids, emulsifiers,and waxes, or solvent-based coatings such as starches, gums, maltodex-trins. For hot melts, cool air is used to harden the carrier, whereas forsolvent-based coatings, hot air is used to evaporate the solvent. Hot-meltingredients release their contents by increasing the temperature or physi-cal breakage, whereas water-soluble coatings release their contents whenwater is added. Fluidized-bed encapsulation can be used to isolate ironfrom ascorbic acid in multivitamins and in small tablets such as childrensvitamins. Many fortified foods, nutritional mixes, and dry mixes, containfluidized-bedencapsulated ingredients. Citric acid, lactic acid, sorbicacid, vitamin C, sodium bicarbonate in baked goods, and salt added topretzels and meats are all encapsulated. Nowadays, the applicabilityand the utility of fluidized-bed coating and other microencapsulationtechniques in the food industry is well recognized, as presented in severalreviews.[6670] There are, however, important factors to be considered in

fluidized-bed coating of food ingredients and additives.Fluidized-bed coating was first developed by D.E. Wurster in the

1950s; hence, the term Wurster process.[70] Today, the fluidized-bedcoating method is being modified by changing the position of the nozzleto be used for coating the solid particles. The different fluidized-bed coat-ing methods are: (1) top-spray, (2) bottom-spray, and (3) tangential-spray. The conventional top-spray method is shown in Fig. 4. The airis passed through a bed of core particles to suspend them in air and coat-ing solution is sprayed countercurrently onto the randomly fluidized

particles. The coated particles travel through the coating zone into theexpansion chamber, and then they fall back into the product containerand continue cycling throughout the process.[71] The top-spray systemhas successfully been used to coat materials as small as 100 mm.[71] How-ever, Thiel and Nguyen demonstrated the possibility of encapsulatingvery fine particles (25mm) by adsorbing them on a coarser carrier, whichis encapsulated by means of conventional fluidized-bed equipment.[72] In


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the top-spray configuration, controlling the distance the droplets travelbefore contacting the substrate is impossible, and coating imperfectionscan occur due to premature droplet evaporation.

The bottom-spray method known as the Wurster system (Fig. 5) iswidely used for coating particles as small as 100 mm. In this method,the particles are recycled through the coating zone at a faster rate andthe fluidization pattern is much more controlled than the top-spraymethod.[73] The typical advantage of this method is that, the path ofthe droplets concurrently toward the core particles is extremely short,

Figure 4. Top-spray fluidized-bed coating.

Figure 5. Bottom-spray fluidized-bed coating.

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so that premature droplet evaporation is almost absent. In addition,coating solution can spread out at the lowest viscosity, producing a verydense film with a superior physical strength. In contrary, Wesdyk et al.reported that particles coated in the bottom spray mode did not displaya uniform film thickness with respect to particle size; larger beads dis-played thicker films compared with smaller beads. The film thicknessvariation could be explained by differences in fluidization patterns. Thisphenomenon did not occur in other configurations.[74]

Recently, a fascinating advancement in fluidized-bed coating tech-nique was reported by Matsuda et al. for the fluidization and coatingof very fine particles.[75] In conventional fluidized-bed coating, whetherit is top-spray, Wurster, or rotational, the basic concept of fluidizationrelies on the compensation of the gravitational force experienced by theparticles by an upward moving air flow, which ensures complete fluidi-zation of the particles. Typical fluidized-bed apparatus can efficientlyprocess particles from 100 mm to a few millimeters. However, for verysmall particles, other forces, such as electrostatic forces, start to playa major role in the movement of the particles in the fluidization cham-ber and prevent adequate fluidization. Colloidal particles have beenused with some success to reduce electrostatic force, but are not muchhelp in the fluidization of very small (submicron) particles in a conven-tional fluidized-bed apparatus. In this innovative process (Fig. 6), how-ever, the gravitational force is multiplied through the use of a rotatingperforated drum that contains the particle. The air flow is then appliedtangentially to the rotation of the drum as compensation for the gravi-tational force, now a multiple (up to 37 g) of the normal gravitationalforce.

The conventional top-spray method remains unique and widely usedtechnique in food industry. This is due to its high versatility, relatively high

batch size, and relative simplicity.[75] Recently, continuous fluidized-bed

Figure 6. Tangential-spray fluidized-bed coating.


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coaters have been developed.[76] With such a continuous fluidized-bedcoating process, manufacturers can adapt the system to their own specificrequirements while maintaining the flexibility needed for a large materialthroughput and wide product ranges, and while providing the coatingquality demanded in the food industry. The efficiency of fluidized-bedtechniques is governed by process variables, ambient variables, and ther-modynamic factors (Table 3). Appropriate modification or combinationsof these variables will yield the desired results.

The use of melted fats, waxes, or emulsifiers as shell materials is arelatively new but very promising and interesting concept. From anindustrial point of view, the inherent advantage of hot-melt fluidized-bed coating lies in the fact that the coating formulation is concentrated(no solvent, as in aqueous-based coating formulation), which meansdramatically shorter processing times. The energy input is also muchlower than with aqueous-based formulation since no evaporation needsto be done. Very few reports have been published on hot-melt coatingby fluidized beds since Jozwiakowsksi et al. described the coating ofsucrose particles with partially hydrogenated cottonseed oil and analyzedthe optimal processing parameters by modified central compositedesign.[77] A number of patent applications, very similar in processingdesigns, have been published using fats and emulsifiers of various meltingpoints and have developed an innovative fluidized-bed process for coat-ing particles with fats and waxes using supercritical carbon dioxide as thesolvent for the coating formulation.[7880] Here, again, minimal energyinput is needed to evaporate the solvent and the process might lead tolower cost-in-use encapsulated ingredients.

Table 3. Different variables influencing fluidized-bed operation

No Variables

1 Process variables1. Inlet air temperature2. Inlet air velocity3. Spray rate4. Solution temperature5. Solution dry matter content

6. Atomization pressure2 Ambient variables

1. Ambient air temperature2. Ambient air relative humidity

3 Thermodynamic1. Outlet air temperature2. Outlet air relative humidity

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APPLICATION OF FLUIDIZED-BED TECHNIQUE

IN FOOD INDUSTRY

This technique is used to encapsulate nutritional substances such asvitamin C, B vitamins, ferrous sulfate, ferrous fumarate, sodium ascor-bate, potassium chloride, and a variety of vitamin=mineral premixes.These encapsulated products are used as nutritional supplements. [81] Inthe case of bakery products, it is also used to encapsulate the leaveningsystem ingredients, as well as vitamin C, acetic acid, lactic acid, potass-ium sorbate, sorbic acid, calcium propionate, and salt.[81,82] In the meatindustry, several food acids have been fluid-bed encapsulated to developcolor and flavor systems. They are also used to achieve a reproducible pHin cured meat products and to shorten their processing time. Fluid-bedencapsulated salt is used in meats to prevent development of rancidity,as well as premature set due to myofibrilar binding.[81]

Extrusion

Encapsulation of food ingredients by extrusion is a relatively new processcompared to spray-drying. Extrusion used in this context is not same asextrusion used for cooking and texturizing of cereal-based products. Actu-ally, extrusion, as applied to flavor encapsulation, is a relatively low-temperature entrapping method, which involves forcing a core material ina molten carbohydrate mass through a series of dies into a bath of dehydrat-ing liquid. The pressure and temperature employed are typically


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core material is removed from the surface in an alcohol bath.[14,51,71,81]

This provides an excellent stability against oxidation and therefore pro-longs the shelf life. The product can be kept for 12 years without anysubstantial quality degradation.[71,81] This technique can be classified asa glass encapsulation system or a controlled-release system, dependingon the polymeric materials used. The polymer matrices and the plastici-zers used can be modified to produce the capsules for controlled releasein food application.[85] However, microcapsules produced from thismethod are commonly designed to be soluble in water by the use ofhigh-molecular-weight hydrophilic polymer. Thus, this encapsulationtechnique is considered unsuitable for subsequent extrusion processingbecause the water in the extruder melt can dissolve the capsules.[86]

Centrifugal Extrusion

Centrifugal extrusion is another encapsulation technique that has beeninvestigated and used by some manufacturers. A number of food-approved

Figure 7. Flow diagram of encapsulation of food flavors by extrusion method.

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coating systems have been formulated to encapsulate products such asflavorings, seasonings, and vitamins. These wall materials include gela-tin, sodium alginate, carrageenan, starches, cellulose derivatives, gumacacia, fats=fatty acids, waxes, and polyethylene glycol. Centrifugalextrusion is a liquid coextrusion process utilizing nozzles consisting ofconcentric orifice located on the outer circumference of a rotating cyl-inder (i.e., head). The encapsulating cylinder or head consists of a con-centric feed tube through which coating and core materials are pumpedseparately to the many nozzles mounted on the outer surface of thedevice. While the core material passes through the center tube, coatingmaterial flows through the outer tube. The entire device is attached to arotating shaft such that the head rotates around its vertical axis. As thehead rotates, the core and coating materials are co-extruded throughthe concentric orifices of the nozzles as a fluid rod of the core sheathedin coating material. Centrifugal force impels the rod outward, causing itto break into tiny particles. By the action of surface tension, the coatingmaterial envelops the core material, thus accomplishing encapsulation.The microcapsules are collected on a moving bed of fine-grained starch,which cushions their impact and absorbs unwanted coating moisture.Particles produced by this method have diameter ranging from 150 to2000 mm.[87]

Lyophilization

Lyophilization, or freeze-drying, is a process used for the dehydration ofalmost all heat-sensitive materials and aromas. It has been used to encap-sulate water-soluble essences and natural aromas as well as drugs. Exceptfor the long dehydration period required (commonly 20 h), freeze-drying

is a simple technique, which is particularly suitable for the encapsulationof aromatic materials. The retention of volatile compounds during thelyophilization is dependent upon the chemical nature of the system. [88]

Coacervation

Coacervation involves the separation of a liquid phase of coatingmaterial from a polymeric solution followed by the coating of that phase

as a uniform layer around suspended core particles. The coating is thensolidified. In general, the batch-type coacervation processes consist ofthree steps and are carried out under continuous agitation.

1. Formation of a three-immiscible chemical phase2. Deposition of the coating3. Solidification of the coating


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In the first step, a three-phase system consisting of a liquid manufac-turing vehicle phase, a core material phase, and a coating material phaseis formed by either a direct addition or in situ separation technique. Inthe direct addition approach, the coating-insoluble waxes, immisciblesolutions, and insoluble liquid polymers are added directly to theliquid-manufacturing vehicle, provided that it is immiscible with theother two phases and is capable of being liquefied. In the in situ separ-ation technique, a monomer is dissolved in the liquid vehicle and is thensubsequently polymerized at the interface. Deposition of the liquid poly-mer coating around the core material is accomplished by controlledphysical mixing of the coating material (while liquid) and the corematerial in the manufacturing vehicle in the liquid phase; this sorptionphenomenon is a prerequisite to effective coating. Continued depositionof the coating is prompted by a reduction in the total free interfacialenergy of the system brought about by a decrease of the coating materialsurface area during coalescence of the liquid polymer droplets. Finally,solidification of the coating is achieved by thermal, cross-linking, or des-olventization techniques and forms a self-sustaining microcapsule. Themicrocapsules are usually collected by filtration or centrifugation,washed with an appropriate solvent, and subsequently dried by standardtechniques such as spray- or fluidized-bed drying to yield free-flowing,discrete particles.[7]

A large numbers of coating materials have been evaluated for coacer-vation microencapsulation but the most studied and well understoodcoating system is probably the gelatin=gum acacia system. However,other coating systems such as gliadin, heparin=gelatin, carrageenan,chitosan, soy protein, polyvinyl alcohol, gelatin=carboxymethylcellulose,B-lactoglobulin=gum acacia, and guar gum=dextran are also studied.[89]

In recent years, modified coacervation processes have also been developed

that can overcome some of the problems encountered during a typicalgelatin=gum acacia complex coacervation process, especially when dealingwith food ingredients; for example, a room-temperature process for theencapsulation of heat-sensitive ingredients such as volatile flavor oils.[90]

In this process, the coating materials are mixed and then phase separation(coacervation) is achieved by adjusting the pH. The newly formed coacer-vate phase is allowed to separate and sediment, most of the supernatantwater is removed, and the flavor oil is then added to the mixture kept at50C and emulsified rapidly. The initial volume of water is restored with

room temperature water, causing a quick drop in the temperature, whichmeans that the flavor oils experience a high temperature for only a fewminutes, compared to several hours for a typical coacervation process.Another process involves the formation of a multilayered coacervatedmicrocapsule.[91] This process consists of multiple coacervation stages inwhich an additional layer of wall material is applied to the microcapsuleat each passage and the final shell layer can reach a thickness up to 100mm.

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The coacervation method has some drawbacks. This process is veryexpensive and rather complex, and cross-linking of the wall materialusually involves glutaraldehyde, which must be carefully used accordingto the countrys legislation. The problems related to harmful chemicalcross-linkers could eventually be solved by using enzymatic cross-linkersinstead. Soper and Thomas, for instance, described a process in which atransglutaminase is used to cross-link the proteins in the shell material.The enzyme is added to the microencapsulation tank at 10C and pH 7and the reaction is carried out over 16 h, after which a hardened shellof coacervate is formed around the flavor oil droplets. [92]

Centrifugal Suspension Separation

Centrifugal suspension is more recent microencapsulation process. Theprocess in principle involves mixing the core and wall materials and thenadding to a rotating disk. The core materials then leave the disk with acoating of residual liquid. The microcapsules are then dried or chilledafter removal from the disk. The whole process can take between a fewseconds to minutes. Solids, liquids, or suspensions of 30 mm to 2mm

can be encapsulated in this manner. Coatings can be 1200 mm in thick-ness and include fats, polyethylene glycol (PEG), diglycerides, and othermeltable substances. Since this is a continuous, high-speed method thatcan coat particles, it is highly suitable for foods. One application is toprotect foods that are sensitive to or readily absorb moisture, such asaspartame, vitamins, or methionine.[93] The preparation process of encap-sulated particles by centrifugal suspension separation is illustrated inFig. 8.

Cocrystallization

Cocrystallization is a new encapsulation process utilizing sucrose as amatrix for the incorporation of core materials. The sucrose syrup is con-centrated to the supersaturated state and maintained at a temperaturehigh enough to prevent crystallization. A predetermined amount of corematerial is then added to the concentrated syrup with vigorous mechanicalagitation, thus providing nucleation for the sucrose=ingredient mixtureto crystallize. As the syrup reaches the temperature at which transform-

ation and crystallization begin, a substantial amount of heat is emitted.Agitation is continued in order to promote and extend transformation=crystallization until the agglomerates are discharged from the vessel.The encapsulated products are then dried to the desired moisture (ifnecessary) and screened to a uniform size. It is very important to properlycontrol the rates of nucleation and crystallization as well as the thermalbalance during the various phases.[94]


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The advantages of this technique include: (1) It can be employed toachieve particle drying. By means of this process, core materials in aliquid form can be converted to a dry powdered form without additionaldrying. (2) Products offer direct tableting characteristics because of theiragglomerated structure and thus offer significant advantages to the candyand pharmaceutical industries. Recently, Beristain et al. encapsulatedorange peel oil by a cocrystallization technique.[95] In their study, encap-sulation capacity of sucrose syrups was found to be greater than 90% fora range of 100 to 250 g oil=kg of sugar. Surface oil, a measurement ofencapsulation efficiency, varied from 3350 to 8880 mg oil=kg solids.Moisture content of the crystals was lower than 10 g=kg, and bulk densitywas greater than 670 kg=m3 for all the cocrystallizates prepared. Sensoryevaluation showed that all of the panelists were able to detect oxidizedflavors in oils without antioxidant added after storage at 35C for oneday. When butylated hydroxyanisole was added to the oil prior to cocrys-tallization, no signs of oxidized flavors were detected after 2 months ofstorage at ambient temperature.

Liposome Entrapment

Liposomes consist of an aqueous phase that is completely surrounded bya phospholipid-based membrane. When phospholipids, such as lecithin,

Figure 8. Representation of rotational suspension separation (A: establishingparticle size for pure coating, and B: encapsulation by suspension separation).

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are dispersed in an aqueous phase, the liposomes form spontaneously.One can have either aqueous or lipid-soluble material enclosed in theliposome. They have been used for delivery of vaccines, hormones,enzymes, and vitamins.[96] They consist of one or more layers of lipidsand thus are nontoxic and acceptable for foods. Permeability, stability,surface activity, and affinity can be varied through size and lipid compo-sition variations. They can range from 25 nm to several microns in diam-eter, are easy to make, and can be stored by freeze-drying. Kirby andGregoriadis have devised a method to encapsulate at high efficiency,which is easy to scale-up and uses mild conditions appropriate forenzymes.[97] It is important to reiterate that large unilamellar vesicles(LUV) are the most appropriate liposomes for the food industry becauseof their high encapsulation efficiency, their simple production methods,and their good stability over time. The great advantage of liposomes overother microencapsulation technologies is the stability liposomes impartto water-soluble material in high water activity application: spray-dryers,extruders, and fluidized beds impart great stability to food ingredients inthe dry state but release their content readily in high water activity appli-cation, giving up all protection properties. Another unique property ofliposomes is the targeted delivery of their content in specific parts of thefoodstuff. For example, it has been shown that liposome-encapsulatedenzymes concentrate preferably in the curd during cheese formation,whereas nonencapsulated enzymes are usually distributed evenly in thewhole milk mixture, which leads to very low (24%) retention of theflavor-producing enzymes in the curd. They have prepared bromelain-loaded liposomes for use as meat-tenderizer to improve stability ofthe enzyme during the processing of the food and subsequently improvethe availability of the enzyme.[98] Benech Kheadr et al. showed thatliposome-entrapped nisin retained higher activity against Listeria inno-cua and had improved stability in cheese production, proving a power-ful tool to inhibit the growth of Listeria I in cheese while not preventingthe detrimental effect of nisin on the actual cheese-ripening process.[99]

Kirby et al. have developed a process to stabilize vitamin C in the aque-ous inner core of liposomes.[100] Encapsulation of vitamin C gave sig-nificant improvements in shelf life (from a few days to up to 2 months),especially in the presence of common food components that would nor-mally speed up decomposition, such as copper ions, ascorbate oxidase,and lysine. Liposomes can also be used to deliver the encapsulated

ingredient at a specific and well-defined temperature: the liposomebilayer is instantly broken down at the transition temperature of thephospholipids, typically around 50C, at which temperature the contentis immediately released.

The most common phospholipid in lectin, phosphatidyl choline, isinsoluble in water and is inexpensively isolated from soy or egg yolk.The composition of the phospholipids and the process used determine


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if a single layer or multiple layers are formed. Fatty acids also make upliposomes and their degree of saturation is dependent on the source. Ani-mal sources provide more saturated fatty acids. They influence the tran-sition temperature, which is the conversion from a gel to the more leakyliquid form. The main issues in liposome encapsulation for the foodindustry are (1) the scaling up of the microencapsulation process atacceptable cost-in-use levels and (2) the delivery form of the liposome-encapsulated ingredients. The development of a cost-effective dryingmethod for liposome microcapsules and development of a dry liposomeformulation that readily reconstitutes upon rehydration would ensurea promising future to liposome encapsulation of food ingredients. Therecent advances in liposome technology have most probably solvedthe first issue: microfluidization has been shown to be an effective,cost-effective, and solvent-free continuous method for the productionof liposomes with high encapsulation efficiency. The method can processa few hundred liters per hour of aqueous liposomes on a continuousbasis.[101,102] The other issue concerns the aqueous form in which the lipo-somes are usually delivered. Most of the time, if not always, liposome for-mulations are kept in relatively dilute aqueous suspensions and this mightbe a very serious drawback for the large-scale production, storage, andshipping of encapsulated food ingredients.

Inclusion Complexation

Molecular inclusion is another means of achieving encapsulation. Unlikeother processes discussed to this point, this technique takes place at amolecular level; b-cyclodextrin is typically used as the encapsulatingmedium.b-Cyclodextrin is a cyclic derivative of starch made up of seven

glucopyranose units. They are prepared from partially hydrolyzed starch(maltodextrin) by an enzymatic process. The external part of the cyclo-dextrin molecule is hydrophilic, whereas the internal part is hydrophobic.The guest molecules, which are apolar, can be entrapped into the apolarinternal cavity through a hydrophobic interaction.[103] This internalcavity of about 0.65 nm diameter permits the inclusion of essential oilcompounds and can take up one or more flavor volatile molecules.[13]

In this method, the flavor compounds are entrapped inside the hollowcenter of ab-cyclodextrin molecule. The chemical structure and geometry

ofb-cyclodextrin are shown in Fig. 9.b-Cyclodextrin molecules form inclusion complexes with compounds

that can fit dimensionally into their central cavity. These complexes areformed in a reaction that takes place only in the presence of water. Mole-cules that are less polar than water (i.e., most flavor substances) and havesuitable molecular dimensions to fit inside the cyclodextrin interior canbe incorporated into the molecule. There are three methods to produce

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the flavor-b-cyclodextrin complex. In the first method, b-cyclodextrin isdissolved in water to form an aqueous solution, and the flavors are addedto form an inclusion complex in crystalline form. The crystal obtainedis then separated and dried. In the second method, b-cyclodextrin isdissolved in a lesser amount of water than in the first method to form

a concentrated suspension, and the flavors are mixed to form an inclusioncomplex in crystalline form. The complex then must be separated anddried. In the third method, b-cyclodextrin is dissolved in a muchlower water content to form a paste, and the flavors are mixed duringkneading to form an inclusion complex. This method is superior to theformer two because it does not require further separation and drying.[103]

A cyclodextrin-complexation method has been patented using a ball millwith a charge of cyclodextrin and a guest molecule. This process needslittle water, preferably 2560% moisture by weight. The inclusion

capacity of 1 g of b-cyclodextrin is not more than 97 mg of lemon oil.Among all existing microencapsulation methods, molecular inclusionof flavor volatiles in b-cyclodextrin molecules is the most effective forprotecting the aromas. Encapsulating flavors in this way can providebetter protection from volatilization during extrusion. However, the useof b-cyclodextrin for food application is very limited, possibly due toregulatory requirements in a number of countries.[86]

Figure 9. Molecular structure and microstructure ofb-cyclodextrin.[79]


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Table4.

Encapsulatedfoodingredientsandthe

irapplicationinfoodindus

try

No.

Categoryof

food

ingredients

Examples

Preferredmodeof

enca

psulation

Applications

1

Acidulants

Lacticacid,glucono

-d-lactone,

vitaminC,acetic

acid,

potassiumsorbate,sorbicacid,

calciumpropiona

te,

andsodiumchlor

ide

Fluidized-b

edcoating,

extrusion

1.

Usedtoassistinthedevelopment

ofcolorandflavorinmeatemuls

ions,

drysa

usageproducts,uncooked

processedmeats,andmeatcontaining

produ

cts.

2.

Bakingindustryusestableacidsa

nd

bakingsodainwetanddrymixes

to

contro

lthereleaseofcarbondiox

ide

duringprocessingandsubsequent

baking.

2

Flavoringagents

Citrusoil,mintoils,

onionoils,garlic

oils,

spiceoleoresins

Inclusioncomplexation,

extrusion

,centrifugal

extrusion

,spray-drying

1.

Totra

nsformliquidflavoringsinto

stable

andfreeflowingpowders,which

areea

siertohandleandincorporate

intoa

dryfoodsystem.

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3

Sweeteners

Sugars,nutritive

orartificialsugars:

aspartame

Cocrystalliza

tion,

fluidized-b

edcoating

1.Toreducethehygroscopicity,improve

flowability,andprolongsweetness

perception.

4

Colorants

Annatto,

b-carotene,

turmeric

Extrusion,emulsion

1.Encaps

ulatedcolorsareeasierto

handle

andofferimprovedsolubility,

stabilitytooxidation,andcontrol

overstratificationfromdryblends.

5

Lipids

Fishoil,

linolenicacid,

ricebrainoil,

eggwhitepowder,

sardineoil,

palmiticacid,

sealblubberoil

Spray-drying

,freeze-drying,

vacuum-drying

1.Topreventoxidativedegradation

during

processingandstorage.

6

Vitaminsand

minerals

Fat-soluble:

vitaminA,

D,

E,a

ndK.

Water-soluble:vita

minC,

vitaminB1,vitaminB2,

vitaminB6,vitaminB12,

niacin,

folicacid

Coacervation,

inclusioncomplexation,

spray-dryi

ng,

liposomeentrapment

1.Toreduceoff-flavors.

2.Topermittime-releaseofnutrients

.

3.Toenh

ancethestabilitytoextremesin

temperatureandmoisture.

4.Toreduceeachnutrientinteraction

otheringredients.

7

Enzymesand

microorganisms

Lipase,invertase,

Brevibacteriumline

ns,

Penicilliumroquefo

rti

Coacervation,

spraymethod,

liposomeentrapment

1.Toimp

rovethestability.

2.Toreducetheripeningtime.

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ENCAPSULATED INGREDIENTS AND APPLICATIONS

Microencapsulation can potentially offer numerous benefits to the mate-rials being encapsulated. Various properties of active agents may bechanged by encapsulation. For example, handling and flow propertiescan be improved by converting liquid to a solid encapsulated from.Hygroscopic materials can be protected from moisture. Some of theencapsulated food ingredients and their applications are summarized inTable 4.

CONCLUSIONS

The use of microencapsulated food ingredients for controlled-releaseapplications is a promising alternative to solve the major problem of foodingredients faced by food industries. The challenges are to select theappropriate microencapsulation technique and encapsulating material.Despite the wide range of encapsulated products that have beendeveloped, manufactured, and successfully marketed in the pharmaceuti-cal and cosmetic industries, microencapsulation has found a compara-tively much smaller market in the food industry. The technology is stillfar from being fully developed and has yet to become a conventional toolin the food technologists repertoire for several reasons. First of all,the development time is rather long and requires multidisciplinarycooperation. Secondly, the low margins typically achieved in food ingre-dients and the relative inertia of well-established corporations are aneffective deterrent to the development and implementation of novel tech-nologies that could result in truly unique food products, whether formore effective production, food fortification, neutraceuticals, improvedorganoleptic properties, or development of novelty food products. How-ever, the most important aspect of R&D, from the very first lab-benchtests, is an understanding of the industrial constraints and requirementsto make a microencapsulation process viable, from the transition tofull-scale production to the marketing of the final product.

ACKNOWLEDGEMENT

This study was supported by a grant of the Korea Health 21 R and DProject, Ministry of Health and Welfare, Republic of Korea (A050376).

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