Recent Developments in Microencapsulation of Food Ingredients

Drying Technology, 23: 1361–1394, 2005 

Copyright Q 2005 Taylor & Francis, Inc. 

ISSN: 0737-3937 print/1532-2300 online 

DOI: 10.1081/DRT-200063478 

Recent Developments in Microencapsulation of 

Food 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 processors 

a means with which to protect sensitive food components, ensure against 

nutritional loss, utilize otherwise sensitive ingredients, incorporate unusual or 

time-release mechanisms into the formulation, mask or preserve flavors and aromas, 

and transform liquids into easily handled solid ingredients. Various techniques 

are employed to form microcapsules, including spray drying, spray chilling 

or spray cooling, extrusion coating, fluidized-bed coating, liposome entrapment, 

coacervation, inclusion complexation, centrifugal extrusion, and rotational 

suspension separation. Recent developments in each of these techniques are 

discussed in this review. Controlled release of food ingredients at the right place 

and the right time is a key functionality that can be provided by microencapsulation. 

A timely and targeted release improves the effectiveness of food additives, broadens 

the application range of food ingredients, and ensures optimal dosage, thereby 

improving the cost effectiveness for the food manufacturer. Reactive, sensitive, or 

volatile additives (vitamins, cultures, flavors, etc.) can be turned into stable ingredients 

through microencapsulation. With carefully fine-tuned controlled-release 

properties, microencapsulation is no longer just an added-value technique, but the 

source of totally new ingredients with matchless properties. 

Keywords: Microencapsulation; Food ingredients; Controlled release; Spray 

drying; 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, Korea 

University, 1, 5-Ka, Anam-Dong, Sungbuk-ku, Seoul 136–701, South Korea; 

Tel.: 82-2-3290-3450; Fax: 82-2-953-5892; E-mail: hjpark@korea.ac.kr

1362 Desai and Park 

their contents at controlled rates under specific conditions. [1–6] The 

microencapsulation technology has been used by the food industry for 

more than 60 years. In a broad sense, encapsulation technology in food 

processing 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 microencapsulation 

and macro-coating techniques, respectively. [7] More 

specifically, the microcapsule has the ability to preserve a substance in 

the finely divided state and to release it as occasion demands. [8] These 

microcapsules may range from submicrometer to several millimeters in 

size and have a multitude of different shapes, depending on the materials 

and methods used to prepare them. The food industry applies microencapsulation 

process for a variety of reasons: (1) encapsulation= 

entrapment can protect the core material from degradation by reducing 

its reactivity to its outside environment (e.g., heat, moisture, air, and 

light), (2) evaporation or transfer rate of the core material to the outside 

environment is decreased=retarded, (3) the physical characteristics of the 

original material can be modified and made easier to handle, (4) the product 

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 property 

delay until the right stimulus), (5) the flavor of the core material can 

be masked, (6) the core material can be diluted when only very small 

amounts are required, yet still achieve a uniform dispersion in the host 

material, and (7) it can be employed to separate components within a 

mixture that would otherwise react with one another. [9–14] 

Various properties of microcapsules that may be changed to suit specific 

ingredient applications include composition, mechanism of release, 

particle size, final physical form, and cost. The architecture of microcapsules 

is generally divided into several arbitrary and overlapping classifications 

(Fig. 1). One such classification is known matrix encapsulation. 

This is the simplest structure, in which a sphere is surrounded by a wall 

or membrane of uniform thickness resembling that of a hen’s egg. In this 

design, the core material is buried to varying depths inside the shell. This 

microcapsule has been termed a single-particle structure (Fig. 1A). It is 

also possible to design microcapsules that have several distinct cores 

within the same microcapsule or, more commonly, number numerous 

core particles embedded in a continuous matrix of wall material. This 

type of design is termed the aggregate structure (Fig. 1B). 

In order to improve the properties of food ingredients, immobilization 

of food ingredients onto a suitable polymer or addition of antimicrobial 

agents are common practices in the food industres. [15–17] For 

example, an important bacteria used in the food industry, lactic acid bacteria, 

was first immobilized in 1975 on Berl saddles and Lactobacillus 

lactis was encapsulated in alginate gel beads years later. [18] Seiss and 

Davis suggested that immobilized lactic acid bacteria could be used to

Microencapsulation of Food Ingredients 1363 

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

continuously produce yogurt. [19] However, the alginate gel beads leaked 

large quantities of cells. 

The use of microencapsulated food ingredients allows food ingredients 

to be carefully tailored to the specific release site through the choice 

and microencapsulation variables, specifically, the method and food 

ingredients-polymer ratio. [7] The total amount of ingestion and the 

kinetics of release are variables that can be manipulated to achieve the 

desired 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 ingredients 

and control the release of food ingredients. 

Various properties of microcapsules that may be changed to suit 

specific ingredient applications include composition, mechanism of 

release, particle size, final physical form, and cost. Before considering 

the properties desired in encapsulated products, the purpose of encapsulation 

must be clear. In designing the encapsulation process, the following 

questions are taken into consideration: 

1. What functionality should the encapsulated ingredients provide the 

final 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 the 

microcapsule? 

5. By what mechanism the ingredient be released from the 

microcapsules? 

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

encapsulated ingredient? 

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


Controlled release may be defined as a method by which one or more 

active agents or ingredients are made available at a desired site and time 

at a specific rate. With the emergence of controlled-release technology, some 

heat-, temperature-, or pH-sensitive additives can be used very conveniently 

in food systems. Such additives are introduced into the food system mostly 

in the form of microcapsules. The additive present in the microcapsule is 

released under the influence of a specific stimulus at a specified stage. For 

example, flavors and nutrients may be released upon consumption, whereas 

sweeteners that are susceptible to heat may be released toward the end of 

baking, thus preventing undesirable caramelization in the baked product. 

[20–30] Although quite a number of reviews are published on the microencapsulationoffoodingredients,wehavemadeanattemptheretoupdate 

the recent developments in the microencapsulation of food ingredients. 

MICROENCAPSULATION TECHNIQUES 

Encapsulation of food ingredients into coating materials can be achieved 

by several methods. The selection of the microencapsulation process is 

governed by the properties (physical and chemical) of core and coating 

materials and the intended application of food ingredients. However, 

the microencapsulation processes that are used to encapsulate food ingredients 

are given in Table 1, which outlines various methods used for the 

preparation of microencapsulated food systems. Sophisticated shell materials 

and technologies have been developed and an extremely wide variety 

of functionalities can now be achieved through microencapsulation. Any 

kind of trigger can be used to prompt the release of the encapsulated 

ingredient, such as pH change (enteric and anti-enteric coating), mechanical 

stress, temperature, enzymatic activity, time, osmotic force, etc. However, 

cost considerations in the food industry are much more stringent 

than in, for instance, the pharmaceutical or cosmetic industries. The 

selection of microencapsulation method and coating materials are interdependent. 

Based on the coating material or method applied, the appropriate 

method or coating material is selected. Coating materials, which 

are basically film-forming materials, can be selected from a wide variety 

of natural or synthetic polymers, depending on the material to be coated 

and characteristics desired in the final microcapsules. 

The composition of the coating material is the main determinant of 

the functional properties of the microcapsule and of how it may be used 

to improve the performance of a particular ingredient. An ideal coating 

material should exhibit the following characteristics: 

1. Good rheological properties at high concentration and easy workability 

during encapsulation. 

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

emulsion produced.


Table 1. Various microencapsulation techniques and the processes involved in 

each technique 

No Microencapsulation technique Major steps in encapsulation 

1 Spray-drying a. Preparation of the dispersion 

b. Homogenization of the dispersion 

c. Atomization of the infeed dispersion 

d. Dehydration of the atomized particles 

2 Spray-cooling a. Preparation of the dispersion 



3 Spray-chilling a. Preparation of the dispersion 



4 Fluidized-bed coating a. Preparation of coating solution 

b. Fluidization of core particles. 

c. Coating of core particles 

5 Extrusion a. Preparation of molten coating solution 

b. Dispersion of core into molten 

polymer 

c. Cooling or passing of core-coat 

mixture through dehydrating liquid 

6 Centrifugal extrusion a. Preparation of core solution 

b. Preparation of coating material 

solution 

c. Co-extrusion of core and coat 

solution through nozzles 

7 Lyophilization a. Mixing of core in a coating solution 

b. Freeze-drying of the mixture 

8 Coacervation a. Formation of a three-immiscible 

chemical phases 

b. Deposition of the coating 

9 Centrifugal suspension 

separation 

c. Solidification of the coating 

a. Mixing of core in a coating material 

b. Pour the mixture over a rotating disc 

to obtain encapsulated tiny particles 

c. Drying 

10 Cocrystallization a. Preparation of supersaturated 

sucrose solution 

b. Adding of core into supersaturated 

solution 

c. Emission of substantial heat after 

solution reaches the sucrose 

crystallization temperature 

(Continued)


Table 1. (Continued) 

No Microencapsulation technique Major steps in encapsulation 

11 Liposome entrapment a. Microfluidization 

b. Ultrasonication 

c. Reverse-phase evaporation 

12 Inclusion complexation Preparation of complexes by mixing or 

grinding or spray-drying 

3. Nonreactivity with the material to be encapsulated both during processing 

and on prolonged storage. 

4. The ability to seal and hold the active material within its structure 

during processing or storage. 

5. The ability to completely release the solvent or other materials used 

during the process of encapsulation under drying or other desolventization 

conditions. 

6. The ability to provide maximum protection to the active material 

against 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 listed 

above, in practice either coating materials are employed in combinations 

or modifiers such as oxygen scavengers, antioxidants, chelating agents, 

and surfactants are added. Some commonly used biocompatible and 

food-grade coating materials are listed in Table 2. However, chemical 

modifications of the existing coating materials to manipulate their 

properties are also being considered. Those modified coating materials 

exhibit better physical and mechanical properties when compared to individual 

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 degradation=oxidation 

and to convert liquids to powders. Spray-drying is the 

most widely used microencapsulation technique in the food industry 

and is typically used for the preparation of dry, stable food additives 

and flavors. The process is economical; flexible, in that it offers substantial 

variation in microencapsulation matrix; adaptable to commonly used 

processing equipment; and produces particles of good quality. In fact,


Table 2. Coating materials for microencapsulation of functional food additives 

Category Coating materials 

Carbohydrate Starch,maltodextrins, 

chitosan, 

corn syrup solids, 

dextran, modified 

starch, cyclodextrins 

Cellulose Carboxymethylcellulose, 

methyl cellulose, 

ethylcellulose, 

celluloseacetate-phthalate, 

celluloseacetatebutylate-phthalate 

Gum Gum acacia, agar, sodium 

alginate, carrageenan 

Lipids Wax, paraffin, beeswax, 

diacylglyerols, oils, fats 

Protein Gluten, casein, gelatin, 

albumin, peptides 

Widely used 

methods References 

Spray- and 

freeze-drying, 

extrusion, 

coacervation, 

inclusion 

complexation 

Coacervation, 

spray-drying, 

and edible films 

20–24 

25–26 

Spray-drying, syringe 27 

method (gel beads) 

Emulsion, liposomes, 28–29 

film formation 

Emulsion, spray-drying 30 

spray-drying production costs are lower than those associated with most 

other methods of encapsulation. One limitation of the spray-drying technology 

is the limited number of shell materials available. Since almost all 

spray-drying processes in the food industry are carried out from aqueous 

feed formulations, the shell material must be soluble in water at an 

acceptable level. Typical shell materials include gum acacia, maltodextrins, 

hydrophobically modified starch, and mixtures thereof. Other polysaccharides 

(alginate, carboxymethylcellulose, guar gum) and proteins 

(whey proteins, soy proteins, sodium caseinate) can be used as the wall 

material in spray-drying, but their usage becomes very tedious and 

expensive because of their low solubility in water: the amount of water 

in the feed to be evaporated is much larger due to the lower dry matter 

content and the amount of active ingredient in the feed must be reduced 

accordingly. In this method, the material for encapsulation is homogenized 

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 of 

the drier. [31] 

Rosenberg and Sheu demonstrated the use of whey protein isolate as 

a wall material for encapsulation of volatiles. [32] They encapsulated ethyl 

butyrate and ethyl caprylate in whey protein isolate and 1:1 mixture of


whey protein isolate and lactose. Retention of volatiles was significantly 

affected by wall solids concentration (10–30%, w=w), initial ester load 

(10–75%,w=w, of wall solids), and by ester and wall type. Ester retention 

in whey protein isolate=lactose was higher than in whey protein isolate. 

Spray-drying is a food manufacturer–friendly technique because it allows 

the food processor to manipulate the preparation process to improve the 

quality of the final product. Recently, Shiga et al. prepared flavorinclusion 

powder by a spray-drying technique using the combined encapsulation 

method of inclusion by b-cyclodextrin and emulsified by gum 

arabic where d-limonene and ethyl n-hexanoate were used as model 

flavors. [33] The effective film-forming property and inclusion complex 

were achieved by applying high pressure to the mixture of flavors and 

b-cyclodextrin slurry using a microfluidizer. It is reported that flavor 

retention during spray-drying increased due to blending of gum arabic 

and b-cyclodextrin in the feed liquid. The release rate of flavors was 

manipulated by the blending of maltodextrin in the feed liquid. In order 

to evaluate the release kinetics of flavors, the release data were fitted to 

Avrami’s equation (Eq. 1). 

R ¼ exp½ ðktÞ n Š ð1Þ 

where R is the retention of flavors during release, t is time, n is a parameter 

representing the release mechanism, and k is the release rate constant. 

Eq. (1) was originally developed the crystal growth of polymers, 

and has been recently used to represent the time-dependent protein 

inactivation in amorphous sugar matrices. [34] In Eq. (1), n ¼ 1 represents 

the first-order reaction, and n ¼ 0.54 represents the diffusion-limiting 

reaction kinetics. [35] Taking a logarithm of both sides of Eq. (1) twice 

yields Eq. (2): 

lnð ln RÞ ¼n ln k þ n ln t ð2Þ 

From Eq. (2) one can find the parameter n as a slope by plotting ln( ln 

R) vs.lnt, and the release rate constant k from the interception at ln t ¼ 0. 

It is important to protect the flavor loss during drying, because 

high-temperature air is commonly used in spray-drying. Generally, the 

retention of flavor in microcapsules is manipulated by varying the 

spray-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 during 

spray-drying, independent of the composition of the feed liquid. However, 

the stability of emulsion droplets markedly affected the retention 

of flavors. d-Limonene emulsion was quite stable independent of the 

emulsifier, while the emulsion of ethyl butyrate was unstable with gum 

arabic as the emulsifier. The use of a mixture of gum arabic and soluble 

soybean polysaccharide as the emulsifier improved oiliness, and adjusting


density of ethyl butyrate and adding gelatin increased the retention of 

ethyl butyrate during spray-drying. 

In recent years, new wall materials for use in spray-drying microencapsulation 

have not really emerged. A few exceptions are noteworthy, 

though. The investigations of other natural gums and their emulsification 

and shell properties have been reported. Mesquite gum, for instance, has 

been shown to give a better stability of the o=w emulsions and higher 

encapsulation efficiency compared to gum acacia. [37,38] Augustin et al. 

proposed the use of Maillard reaction products (MRPs) obtained by 

the reaction at high temperature between protein and carbohydrate to 

encapsulate oxidation-sensitive nutrients such as fish oils. [39] The MRPs 

are known to exhibit antioxidant properties and form a stable and robust 

shell around the oil phase. The stability of the oil against oxidation was 

greatly improved compared to nonencapsulated spray-dried samples in 

ordinary shell material. More interesting is the recent development of 

complex shell formulations for spray-drying encapsulation. For instance, 

aqueous two-phase systems (ATPSs), which result from the phase separation 

of a mixture of soluble polymers in a common solvent due to the 

low entropy of mixing (DS mix) of polymer mixtures, can be used to design 

double-encapsulated ingredients in a single spray-drying step. Millqvist- 

Fureby et al. encapsulated Enterococcus fæcium in a mixture of polyvinylpyrrolidone 

(PVP) and dextran. [40] While proteins exhibit partitioning 

between the two phases, whole cells tend to concentrate in one of the 

polymer phases, which make them ideal candidates for ATPS spray-drying. 

The structure of the microcapsule, whether PVP is the outer layer and 

dextran the inner core or vice versa, can be controlled by adjusting the ratio 

and concentration of the two polymers. Encapsulated E. fæcium in spraydried 

ATPS showed a survival rate of up to 45% after4weeksatroom 

temperature. Another example is the preparation and spray-drying of multiple 

emulsions, which results a in a double-layered microcapsule, providing 

better protection to sensitive materials such as oxidation-probe flavor oils. 

Edris and Bergmtahl have encapsulated orange oil by first preparing a triple 

emulsion o=w=o=w and then evaporating the outer continuous aqueous 

phase, which contains sodium caseinate and lactose as shell material, by 

spray-drying. [41] The process leads to a dry free-flowing powder constituting 

of a double o=w=o, in which the inner orange oil phase is dispersed in an 

aqueous phase, which is itself dispersed in an oil phase encapsulated in 

sodium caseinate and lactose. This double emulsion process is not practically 

more complex than a typical spray-drying process that requires an 

emulsion step anyway. However, preparing a second emulsion implies a 

dilution of the flavor oil, and the much lower payload in the microcapsule 

(5–10%) is a drawback compared to typical spray-dried flavor oils, which 

have payloads of around 20–25%. The unique protection and delayedrelease 

properties obtained with two layers might compensate for the lower 

payload, but this has still to be demonstrated.


Chitosan is a hydrophilic, biocompatible, and biodegradable, polysaccharide 

of low toxicity. In recent years, it has been used for development 

of oral controlled drug delivery systems. It is also a well-known 

dietary food additive. Therefore, our research team demonstrated the 

cross-linked chitosan as a wall material for the encapsulation of vitamin 

C by a spray-drying technique. Vitamin C, a representative water-soluble 

vitamin, has a variety of biological, pharmaceutical, and dermatological 

functions. Vitamin C is widely used in various types of foods as a vitamin 

supplement and as an antioxidant. Hence, in previous studies, sustainedrelease 

carriers of vitamin C have been prepared by using cross-linked 

chitosan as a wall material by spray-drying technique. [42–44] The process 

of the preparation of vitamin C–encapsulated chitosan microcapsules is 

shown in Fig. 2. Chitosan was cross-linked with nontoxic cross-linking 

agent, i.e., tripolyphosphate. Vitamin C–encapsulated chitosan microspheres 

of different size, surface morphology, loading efficiency, and zeta 

potential with controlled-release property could be obtained by varying 

the manufacturing parameters (inlet temperature, flow rate) and using 

the different molecular weight and concentration of chitosan. Vitamin 

C–encapsulated chitosan microcapsules were spherical in shape with a 

smooth surface as observed by scanning electron microscopy (Fig. 3). 

Microencapsulation of vitamin C improves and broadens its applications 

in the food industry. 

Figure 2. Procedure of preparation of vitamin C–encapsulated chitosan 

microspheres by spray-drying.


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

microcapsule. 

Numerous materials have been used as flavor-encapsulating agents 

using a spray-drying technique. These include proteins, gums, and modified 

starches. [45] An area of research of increasing interest is the development 

of alternative and inexpensive polymers that may be considered 

natural, like gum arabic, and that could encapsulate flavors with the 

same efficiency as gum arabic. [46] Mesquite gum has been reported as a 

very good encapsulating agent. [47,48] Beristain and Vernon-Carter noted 

that a blend of 60% gum arabic and 40% mesquite gum encapsulated 

93.5% of orange peel oil. [49] More recently, Beristain et al. reported that 

a mixture consisting of 40% mesquite gum and 60% maltodextrins was 

able to encapsulate 84.6% of the starting oil. [50] Cardamom-based oil 

microcapsules were successfully produced by spray-drying using mesquite 

gum. [38] The stability against drop coalescence of the emulsions was elevated 

for all the gum:oil ratios studied. High flavor retention (83.6%) was 

attained during microencapsulation by spray-drying when a proportion 

of 4:1 gum:oil was used. This confirmed the interesting emulsifying 

properties and good flavor-encapsulation ability that qualify mesquite 

gum as an important alternative encapsulating medium. The microcapsules 

can be readily used as a food ingredient. 

Recent developments have been in the use of new carrier materials 

and a newly designed spray dryer. Colloides Naturels and TIC Gums


have developed new combinations of gum arabic starches to increase 

the retention of volatiles and shelf life of microcapsules. [51,52] Risch and 

Reineccius enhanced the retention of orange oil and decreased oxidation 

by using gum arabic. [53] Bhandari et al. showed that a new type of dryer 

called the Leaflish spray dryer, which uses a high air velocity with a temperature 

of 300 to 400 C, was effective for encapsulating citral and linalyl 

acetate without degradation. [54] A disadvantage is that a separate 

agglomeration step is required to prevent separation or to render the 

obtained powder soluble. A chief advantage is that this technique can 

be used for heat-labile materials. Recently, studies on the modification 

of spray-drying chamber configurations and atomization along applications 

of computational fluid dynamic model have been reported to 

broaden the applications range of spray-drying methods. [55–60] 

Spray-Chilling or Spray-Cooling 

In spray-chilling and spray-cooling, the core and wall mixtures are 

atomized into the cooled or chilled air, which causes the wall to solidify 

around the core. Unlike spray-drying, spray-chilling or spray-cooling 

does not involve evaporation of water. In spray-cooling, the coating 

material is typically some form of vegetable oil or its derivatives. However, 

a wide range of other encapsulating materials may be employed. 

These include fat and stearin with melting points of 45–122 C, as well 

as hard mono- and diacylglycerols with melting points of 45–65 C. [31] 

In spray-chilling, the coating material is typically a fractionated or hydrogenated 

vegetable oil with a melting point in the range of 32–42 C. [61] In 

spray-chilling, there is no mass transfer (i.e., evaporation from the atomized 

droplets); therefore these solidify into almost perfect spheres to 

give free-flowing powders. Atomization gives an enormous surface area 

and an immediate as well as intimate mixing of these droplets with the 

cooling medium. Microcapsules prepared by spray-chilling and spraycooling 

are insoluble in water due to the lipid coating. Consequently, 

these techniques tend to be utilized for encapsulating water-soluble core 

materials such as minerals, water-soluble vitamins, enzymes, acidulants, 

and some flavors. [62] 

Fluidized-Bed Coating 

Originally developed as a pharmaceutical technique, fluidized-bed coating 

is now increasingly being applied in the food industry to fine-tune 

the effect of functional ingredients and additives. The main benefits of 

such miniature packages, called microcapsules, include increased shelf 

life, taste masking, ease of handling, controlled release, and improved 

aesthetics, taste, and color. Fluidized-bed coating increasingly supplies


the food industry with a wide variety of encapsulated versions of food 

ingredients and additives. [63] Compared to pharmaceutical fluidized-bed 

coating, food industry fluidized-bed coating is more obliged to cut 

production costs and, therefore, should adopt a somewhat different 

approach to this rather expensive technology. Solid particles are suspended 

in a temperature and humidity-controlled chamber of highvelocity 

air where the coating material is atomized. [64,65] Typical food 

processing applications of fluidization include freezing and cooling, drying, 

puffing, freeze-drying, spray-drying, agglomeration and granulation, 

classification, and blanching and cooking. [66] Great variations in available 

wall materials exist. Cellulose derivatives, dextrins, emulsifiers, 

lipids, protein derivatives, and starch derivatives are examples of typical 

coating systems, and they may be used in a molten state or dissolved in an 

evaporable solvent. This technique is applicable for hot-melt coatings 

such as hydrogenated vegetable oil, stearines, fatty acids, emulsifiers, 

and waxes, or solvent-based coatings such as starches, gums, maltodextrins. 

For hot melts, cool air is used to harden the carrier, whereas for 

solvent-based coatings, hot air is used to evaporate the solvent. Hot-melt 

ingredients release their contents by increasing the temperature or physical 

breakage, whereas water-soluble coatings release their contents when 

water is added. Fluidized-bed encapsulation can be used to isolate iron 

from ascorbic acid in multivitamins and in small tablets such as children’s 

vitamins. Many fortified foods, nutritional mixes, and dry mixes, contain 

fluidized-bed–encapsulated ingredients. Citric acid, lactic acid, sorbic 

acid, vitamin C, sodium bicarbonate in baked goods, and salt added to 

pretzels and meats are all encapsulated. Nowadays, the applicability 

and the utility of fluidized-bed coating and other microencapsulation 

techniques in the food industry is well recognized, as presented in several 

reviews. [66–70] 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-bed 

coating method is being modified by changing the position of the nozzle 

to be used for coating the solid particles. The different fluidized-bed coating 

methods are: (1) top-spray, (2) bottom-spray, and (3) tangentialspray. 

The conventional top-spray method is shown in Fig. 4. The air 

is passed through a bed of core particles to suspend them in air and coating 

solution is sprayed countercurrently onto the randomly fluidized 

particles. The coated particles travel through the coating zone into the 

expansion chamber, and then they fall back into the product container 

and continue cycling throughout the process. [71] The top-spray system 

has successfully been used to coat materials as small as 100 mm. [71] However, 

Thiel and Nguyen demonstrated the possibility of encapsulating 

very fine particles (2–5 mm) by adsorbing them on a coarser carrier, which 

is encapsulated by means of conventional fluidized-bed equipment. [72] In


Figure 4. Top-spray fluidized-bed coating. 

the top-spray configuration, controlling the distance the droplets travel 

before contacting the substrate is impossible, and coating imperfections 

can occur due to premature droplet evaporation. 

The bottom-spray method known as the Wurster system (Fig. 5) is 

widely used for coating particles as small as 100 mm. In this method, 

the particles are recycled through the coating zone at a faster rate and 

the fluidization pattern is much more controlled than the top-spray 

method. [73] The typical advantage of this method is that, the path of 

the droplets concurrently toward the core particles is extremely short, 

Figure 5. Bottom-spray fluidized-bed coating.


so that premature droplet evaporation is almost absent. In addition, 

coating solution can spread out at the lowest viscosity, producing a very 

dense film with a superior physical strength. In contrary, Wesdyk et al. 

reported that particles coated in the bottom spray mode did not display 

a uniform film thickness with respect to particle size; larger beads displayed 

thicker films compared with smaller beads. The film thickness 

variation could be explained by differences in fluidization patterns. This 

phenomenon did not occur in other configurations. [74] 

Recently, a fascinating advancement in fluidized-bed coating technique 

was reported by Matsuda et al. for the fluidization and coating 

of very fine particles. [75] In conventional fluidized-bed coating, whether 

it is top-spray, Wurster, or rotational, the basic concept of fluidization 

relies on the compensation of the gravitational force experienced by the 

particles by an upward moving air flow, which ensures complete fluidization 

of the particles. Typical fluidized-bed apparatus can efficiently 

process particles from 100 mm to a few millimeters. However, for very 

small particles, other forces, such as electrostatic forces, start to play 

a major role in the movement of the particles in the fluidization chamber 

and prevent adequate fluidization. Colloidal particles have been 

used with some success to reduce electrostatic force, but are not much 

help in the fluidization of very small (submicron) particles in a conventional 

fluidized-bed apparatus. In this innovative process (Fig. 6), however, 

the gravitational force is multiplied through the use of a rotating 

perforated drum that contains the particle. The air flow is then applied 

tangentially to the rotation of the drum as compensation for the gravitational 

force, now a multiple (up to 37 g) of the normal gravitational 

force. 

The conventional top-spray method remains unique and widely used 

technique 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.


coaters have been developed. [76] With such a continuous fluidized-bed 

coating process, manufacturers can adapt the system to their own specific 

requirements while maintaining the flexibility needed for a large material 

throughput and wide product ranges, and while providing the coating 

quality demanded in the food industry. The efficiency of fluidized-bed 

techniques is governed by process variables, ambient variables, and thermodynamic 

factors (Table 3). Appropriate modification or combinations 

of these variables will yield the desired results. 

The use of melted fats, waxes, or emulsifiers as shell materials is a 

relatively new but very promising and interesting concept. From an 

industrial point of view, the inherent advantage of hot-melt fluidizedbed 

coating lies in the fact that the coating formulation is concentrated 

(no solvent, as in aqueous-based coating formulation), which means 

dramatically shorter processing times. The energy input is also much 

lower than with aqueous-based formulation since no evaporation needs 

to be done. Very few reports have been published on hot-melt coating 

by fluidized beds since Jozwiakowsksi et al. described the coating of 

sucrose particles with partially hydrogenated cottonseed oil and analyzed 

the optimal processing parameters by modified central composite 

design. [77] A number of patent applications, very similar in processing 

designs, have been published using fats and emulsifiers of various melting 

points and have developed an innovative fluidized-bed process for coating 

particles with fats and waxes using supercritical carbon dioxide as the 

solvent for the coating formulation. [78–80] Here, again, minimal energy 

input is needed to evaporate the solvent and the process might lead to 

lower cost-in-use encapsulated ingredients. 

Table 3. Different variables influencing fluidized-bed operation 

No Variables 

1 Process variables 

1. Inlet air temperature 

2. Inlet air velocity 

3. Spray rate 

4. Solution temperature 

5. Solution dry matter content 

6. Atomization pressure 

2 Ambient variables 

1. Ambient air temperature 

2. Ambient air relative humidity 

3 Thermodynamic 

1. Outlet air temperature 

2. Outlet air relative humidity


APPLICATION OF FLUIDIZED-BED TECHNIQUE 

IN FOOD INDUSTRY 

This technique is used to encapsulate nutritional substances such as 

vitamin C, B vitamins, ferrous sulfate, ferrous fumarate, sodium ascorbate, 

potassium chloride, and a variety of vitamin=mineral premixes. 

These encapsulated products are used as nutritional supplements. [81] In 

the case of bakery products, it is also used to encapsulate the leavening 

system ingredients, as well as vitamin C, acetic acid, lactic acid, potassium 

sorbate, sorbic acid, calcium propionate, and salt. [81,82] In the meat 

industry, several food acids have been fluid-bed encapsulated to develop 

color and flavor systems. They are also used to achieve a reproducible pH 

in cured meat products and to shorten their processing time. Fluid-bed 

encapsulated 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 process 

compared to spray-drying. Extrusion used in this context is not same as 

extrusion used for cooking and texturizing of cereal-based products. Actually, 

extrusion, as applied to flavor encapsulation, is a relatively lowtemperature 

entrapping method, which involves forcing a core material in 

a molten carbohydrate mass through a series of dies into a bath of dehydrating 

liquid. The pressure and temperature employed are typically


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

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

This provides an excellent stability against oxidation and therefore prolongs 

the shelf life. The product can be kept for 1–2 years without any 

substantial quality degradation. [71,81] This technique can be classified as 

a glass encapsulation system or a controlled-release system, depending 

on the polymeric materials used. The polymer matrices and the plasticizers 

used can be modified to produce the capsules for controlled release 

in food application. [85] However, microcapsules produced from this 

method are commonly designed to be soluble in water by the use of 

high-molecular-weight hydrophilic polymer. Thus, this encapsulation 

technique is considered unsuitable for subsequent extrusion processing 

because the water in the extruder melt can dissolve the capsules. [86] 

Centrifugal Extrusion 

Centrifugal extrusion is another encapsulation technique that has been 

investigated and used by some manufacturers. A number of food-approved


coating systems have been formulated to encapsulate products such as 

flavorings, seasonings, and vitamins. These wall materials include gelatin, 

sodium alginate, carrageenan, starches, cellulose derivatives, gum 

acacia, fats=fatty acids, waxes, and polyethylene glycol. Centrifugal 

extrusion is a liquid coextrusion process utilizing nozzles consisting of 

concentric orifice located on the outer circumference of a rotating cylinder 

(i.e., head). The encapsulating cylinder or head consists of a concentric 

feed tube through which coating and core materials are pumped 

separately to the many nozzles mounted on the outer surface of the 

device. While the core material passes through the center tube, coating 

material flows through the outer tube. The entire device is attached to a 

rotating shaft such that the head rotates around its vertical axis. As the 

head rotates, the core and coating materials are co-extruded through 

the concentric orifices of the nozzles as a fluid rod of the core sheathed 

in coating material. Centrifugal force impels the rod outward, causing it 

to break into tiny particles. By the action of surface tension, the coating 

material 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 to 

2000 mm. [87] 

Lyophilization 

Lyophilization, or freeze-drying, is a process used for the dehydration of 

almost all heat-sensitive materials and aromas. It has been used to encapsulate 

water-soluble essences and natural aromas as well as drugs. Except 

for the long dehydration period required (commonly 20 h), freeze-drying 

is a simple technique, which is particularly suitable for the encapsulation 

of aromatic materials. The retention of volatile compounds during the 

lyophilization is dependent upon the chemical nature of the system. [88] 

Coacervation 

Coacervation involves the separation of a liquid phase of coating 

material from a polymeric solution followed by the coating of that phase 

as a uniform layer around suspended core particles. The coating is then 

solidified. In general, the batch-type coacervation processes consist of 

three steps and are carried out under continuous agitation. 

1. Formation of a three-immiscible chemical phase 

2. Deposition of the coating 

3. Solidification of the coating


In the first step, a three-phase system consisting of a liquid manufacturing 

vehicle phase, a core material phase, and a coating material phase 

is formed by either a direct addition or in situ separation technique. In 

the direct addition approach, the coating-insoluble waxes, immiscible 

solutions, and insoluble liquid polymers are added directly to the 

liquid-manufacturing vehicle, provided that it is immiscible with the 

other two phases and is capable of being liquefied. In the in situ separation 

technique, a monomer is dissolved in the liquid vehicle and is then 

subsequently polymerized at the interface. Deposition of the liquid polymer 

coating around the core material is accomplished by controlled 

physical mixing of the coating material (while liquid) and the core 

material in the manufacturing vehicle in the liquid phase; this sorption 

phenomenon is a prerequisite to effective coating. Continued deposition 

of the coating is prompted by a reduction in the total free interfacial 

energy of the system brought about by a decrease of the coating material 

surface area during coalescence of the liquid polymer droplets. Finally, 

solidification of the coating is achieved by thermal, cross-linking, or desolventization 

techniques and forms a self-sustaining microcapsule. The 

microcapsules are usually collected by filtration or centrifugation, 

washed with an appropriate solvent, and subsequently dried by standard 

techniques such as spray- or fluidized-bed drying to yield free-flowing, 

discrete particles. [7] 

A large numbers of coating materials have been evaluated for coacervation 

microencapsulation but the most studied and well understood 

coating 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 typical 

gelatin=gum acacia complex coacervation process, especially when dealing 

with food ingredients; for example, a room-temperature process for the 

encapsulation 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 coacervate 

phase is allowed to separate and sediment, most of the supernatant 

water is removed, and the flavor oil is then added to the mixture kept at 

50 C and emulsified rapidly. The initial volume of water is restored with 

room temperature water, causing a quick drop in the temperature, which 

means that the flavor oils experience a high temperature for only a few 

minutes, compared to several hours for a typical coacervation process. 

Another process involves the formation of a multilayered coacervated 

microcapsule. [91] This process consists of multiple coacervation stages in 

which an additional layer of wall material is applied to the microcapsule 

at each passage and the final shell layer can reach a thickness up to 100 mm.


The coacervation method has some drawbacks. This process is very 

expensive and rather complex, and cross-linking of the wall material 

usually involves glutaraldehyde, which must be carefully used according 

to the country’s legislation. The problems related to harmful chemical 

cross-linkers could eventually be solved by using enzymatic cross-linkers 

instead. Soper and Thomas, for instance, described a process in which a 

transglutaminase is used to cross-link the proteins in the shell material. 

The enzyme is added to the microencapsulation tank at 10 C and pH 7 

and the reaction is carried out over 16 h, after which a hardened shell 

of coacervate is formed around the flavor oil droplets. [92] 

Centrifugal Suspension Separation 

Centrifugal suspension is more recent microencapsulation process. The 

process in principle involves mixing the core and wall materials and then 

adding to a rotating disk. The core materials then leave the disk with a 

coating of residual liquid. The microcapsules are then dried or chilled 

after removal from the disk. The whole process can take between a few 

seconds to minutes. Solids, liquids, or suspensions of 30 mm to2mm 

can be encapsulated in this manner. Coatings can be 1–200 mm in thickness 

and include fats, polyethylene glycol (PEG), diglycerides, and other 

meltable substances. Since this is a continuous, high-speed method that 

can coat particles, it is highly suitable for foods. One application is to 

protect foods that are sensitive to or readily absorb moisture, such as 

aspartame, vitamins, or methionine. [93] The preparation process of encapsulated 

particles by centrifugal suspension separation is illustrated in 

Fig. 8. 

Cocrystallization 

Cocrystallization is a new encapsulation process utilizing sucrose as a 

matrix for the incorporation of core materials. The sucrose syrup is concentrated 

to the supersaturated state and maintained at a temperature 

high enough to prevent crystallization. A predetermined amount of core 

material is then added to the concentrated syrup with vigorous mechanical 

agitation, thus providing nucleation for the sucrose=ingredient mixture 

to crystallize. As the syrup reaches the temperature at which transformation 

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 (if 

necessary) and screened to a uniform size. It is very important to properly 

control the rates of nucleation and crystallization as well as the thermal 

balance during the various phases. [94]


Figure 8. Representation of rotational suspension separation (A: establishing 

particle size for pure coating, and B: encapsulation by suspension separation). 

The advantages of this technique include: (1) It can be employed to 

achieve particle drying. By means of this process, core materials in a 

liquid form can be converted to a dry powdered form without additional 

drying. (2) Products offer direct tableting characteristics because of their 

agglomerated structure and thus offer significant advantages to the candy 

and pharmaceutical industries. Recently, Beristain et al. encapsulated 

orange peel oil by a cocrystallization technique. [95] In their study, encapsulation 

capacity of sucrose syrups was found to be greater than 90% for 

a range of 100 to 250 g oil=kg of sugar. Surface oil, a measurement of 

encapsulation efficiency, varied from 3350 to 8880 mg oil=kg solids. 

Moisture content of the crystals was lower than 10 g=kg, and bulk density 

was greater than 670 kg=m 3 for all the cocrystallizates prepared. Sensory 

evaluation showed that all of the panelists were able to detect oxidized 

flavors in oils without antioxidant added after storage at 35 C for one 

day. When butylated hydroxyanisole was added to the oil prior to cocrystallization, 

no signs of oxidized flavors were detected after 2 months of 

storage at ambient temperature. 

Liposome Entrapment 

Liposomes consist of an aqueous phase that is completely surrounded by 

a phospholipid-based membrane. When phospholipids, such as lecithin,


are dispersed in an aqueous phase, the liposomes form spontaneously. 

One can have either aqueous or lipid-soluble material enclosed in the 

liposome. They have been used for delivery of vaccines, hormones, 

enzymes, and vitamins. [96] They consist of one or more layers of lipids 

and thus are nontoxic and acceptable for foods. Permeability, stability, 

surface activity, and affinity can be varied through size and lipid composition 

variations. They can range from 25 nm to several microns in diameter, 

are easy to make, and can be stored by freeze-drying. Kirby and 

Gregoriadis have devised a method to encapsulate at high efficiency, 

which is easy to scale-up and uses mild conditions appropriate for 

enzymes. [97] It is important to reiterate that large unilamellar vesicles 

(LUV) are the most appropriate liposomes for the food industry because 

of their high encapsulation efficiency, their simple production methods, 

and their good stability over time. The great advantage of liposomes over 

other microencapsulation technologies is the stability liposomes impart 

to water-soluble material in high water activity application: spray-dryers, 

extruders, and fluidized beds impart great stability to food ingredients in 

the dry state but release their content readily in high water activity application, 

giving up all protection properties. Another unique property of 

liposomes is the targeted delivery of their content in specific parts of the 

foodstuff. For example, it has been shown that liposome-encapsulated 

enzymes concentrate preferably in the curd during cheese formation, 

whereas nonencapsulated enzymes are usually distributed evenly in the 

whole milk mixture, which leads to very low (2–4%) retention of the 

flavor-producing enzymes in the curd. They have prepared bromelainloaded 

liposomes for use as meat-tenderizer to improve stability of 

the enzyme during the processing of the food and subsequently improve 

the availability of the enzyme. [98] Benech Kheadr et al. showed that 

liposome-entrapped nisin retained higher activity against Listeria innocua 

and had improved stability in cheese production, proving a powerful 

tool to inhibit the growth of Listeria I in cheese while not preventing 

the detrimental effect of nisin on the actual cheese-ripening process. [99] 

Kirby et al. have developed a process to stabilize vitamin C in the aqueous 

inner core of liposomes. [100] Encapsulation of vitamin C gave significant 

improvements in shelf life (from a few days to up to 2 months), 

especially in the presence of common food components that would normally 

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 liposome 

bilayer is instantly broken down at the transition temperature of the 

phospholipids, typically around 50 C, at which temperature the content 

is immediately released. 

The most common phospholipid in lectin, phosphatidyl choline, is 

insoluble in water and is inexpensively isolated from soy or egg yolk. 

The composition of the phospholipids and the process used determine


if a single layer or multiple layers are formed. Fatty acids also make up 

liposomes and their degree of saturation is dependent on the source. Animal 

sources provide more saturated fatty acids. They influence the transition 

temperature, which is the conversion from a gel to the more leaky 

liquid form. The main issues in liposome encapsulation for the food 

industry are (1) the scaling up of the microencapsulation process at 

acceptable cost-in-use levels and (2) the delivery form of the liposomeencapsulated 

ingredients. The development of a cost-effective drying 

method for liposome microcapsules and development of a dry liposome 

formulation that readily reconstitutes upon rehydration would ensure 

a promising future to liposome encapsulation of food ingredients. The 

recent advances in liposome technology have most probably solved 

the first issue: microfluidization has been shown to be an effective, 

cost-effective, and solvent-free continuous method for the production 

of liposomes with high encapsulation efficiency. The method can process 

a few hundred liters per hour of aqueous liposomes on a continuous 

basis. [101,102] The other issue concerns the aqueous form in which the liposomes 

are usually delivered. Most of the time, if not always, liposome formulations 

are kept in relatively dilute aqueous suspensions and this might 

be a very serious drawback for the large-scale production, storage, and 

shipping of encapsulated food ingredients. 

Inclusion Complexation 

Molecular inclusion is another means of achieving encapsulation. Unlike 

other processes discussed to this point, this technique takes place at a 

molecular level; b-cyclodextrin is typically used as the encapsulating 

medium. 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 cyclodextrin 

molecule is hydrophilic, whereas the internal part is hydrophobic. 

The guest molecules, which are apolar, can be entrapped into the apolar 

internal cavity through a hydrophobic interaction. [103] This internal 

cavity of about 0.65 nm diameter permits the inclusion of essential oil 

compounds and can take up one or more flavor volatile molecules. [13] 

In this method, the flavor compounds are entrapped inside the hollow 

center of a b-cyclodextrin molecule. The chemical structure and geometry 

of b-cyclodextrin are shown in Fig. 9. 

b-Cyclodextrin molecules form inclusion complexes with compounds 

that can fit dimensionally into their central cavity. These complexes are 

formed in a reaction that takes place only in the presence of water. Molecules 

that are less polar than water (i.e., most flavor substances) and have 

suitable molecular dimensions to fit inside the cyclodextrin interior can 

be incorporated into the molecule. There are three methods to produce


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

the flavor-b-cyclodextrin complex. In the first method, b-cyclodextrin is 

dissolved in water to form an aqueous solution, and the flavors are added 

to form an inclusion complex in crystalline form. The crystal obtained 

is then separated and dried. In the second method, b-cyclodextrin is 

dissolved in a lesser amount of water than in the first method to form 

a concentrated suspension, and the flavors are mixed to form an inclusion 

complex in crystalline form. The complex then must be separated and 

dried. In the third method, b-cyclodextrin is dissolved in a much 

lower water content to form a paste, and the flavors are mixed during 

kneading to form an inclusion complex. This method is superior to the 

former two because it does not require further separation and drying. [103] 

A cyclodextrin-complexation method has been patented using a ball mill 

with a charge of cyclodextrin and a guest molecule. This process needs 

little water, preferably 25–60% 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 inclusion 

of flavor volatiles in b-cyclodextrin molecules is the most effective for 

protecting the aromas. Encapsulating flavors in this way can provide 

better protection from volatilization during extrusion. However, the use 

of b-cyclodextrin for food application is very limited, possibly due to 

regulatory requirements in a number of countries. [86]

1386 

Table 4. Encapsulated food ingredients and their application in food industry 

Preferred mode of 

encapsulation Applications 

Category of food 

ingredients Examples 

No. 

1. Used to assist in the development 

of color and flavor in meat emulsions, 

dry sausage products, uncooked 

processed meats, and meat containing 

products. 

2. Baking industry use stable acids and 

baking soda in wet and dry mixes to 

control the release of carbon dioxide 

during processing and subsequent 

Fluidized-bed coating, 

extrusion 

1 Acidulants Lactic acid, glucono-d-lactone, 

vitamin C, acetic acid, 

potassium sorbate, sorbic acid, 

calcium propionate, 

and sodium chloride 

baking. 

1. To transform liquid flavorings into 

stable and free flowing powders, which 

are easier to handle and incorporate 

into a dry food system. 

Inclusion complexation, 

extrusion, centrifugal 

extrusion, spray-drying 

2 Flavoring agents Citrus oil, mint oils, 

onion oils, garlic oils, 

spice oleoresins

3 Sweeteners Sugars, nutritive 

Cocrystallization, 

1. To reduce the hygroscopicity, improve 

or artificial sugars: 

fluidized-bed coating flowability, and prolong sweetness 

aspartame 

perception. 

4 Colorants Annatto, b-carotene, turmeric Extrusion, emulsion 1. Encapsulated colors are easier to 

handle and offer improved solubility, 

stability to oxidation, and control 

over stratification from dry blends. 

5 Lipids Fish oil, linolenic acid, 

Spray-drying, freeze-drying, 1. To prevent oxidative degradation 

rice brain oil, 

vacuum-drying 

during processing and storage. 

egg white powder, 

sardine oil, 

palmitic acid, 

1. To reduce off-flavors. 

2. To permit time-release of nutrients. 

3. To enhance the stability to extremes in 

temperature and moisture. 

4. To reduce each nutrient interaction 

Coacervation, 

inclusion complexation, 

spray-drying, 

liposome entrapment 

seal blubber oil 

Fat-soluble: 

vitamin A, D, E, and K. 

Water-soluble: vitamin C, 

vitamin B1, vitamin B2, 

vitamin B6, vitamin B12, 

niacin, folic acid 

Lipase, invertase, 

Brevibacterium linens, 

Penicillium roqueforti 

6 Vitamins and 

minerals 

other ingredients. 

1. To improve the stability. 

2. To reduce the ripening time. 

Coacervation, 

spray method, 

liposome entrapment 

7 Enzymes and 

microorganisms 

1387


ENCAPSULATED INGREDIENTS AND APPLICATIONS 

Microencapsulation can potentially offer numerous benefits to the materials 

being encapsulated. Various properties of active agents may be 

changed by encapsulation. For example, handling and flow properties 

can be improved by converting liquid to a solid encapsulated from. 

Hygroscopic materials can be protected from moisture. Some of the 

encapsulated food ingredients and their applications are summarized in 

Table 4. 

CONCLUSIONS 

The use of microencapsulated food ingredients for controlled-release 

applications is a promising alternative to solve the major problem of food 

ingredients faced by food industries. The challenges are to select the 

appropriate microencapsulation technique and encapsulating material. 

Despite the wide range of encapsulated products that have been 

developed, manufactured, and successfully marketed in the pharmaceutical 

and cosmetic industries, microencapsulation has found a comparatively 

much smaller market in the food industry. The technology is still 

far from being fully developed and has yet to become a conventional tool 

in the food technologist’s repertoire for several reasons. First of all, 

the development time is rather long and requires multidisciplinary 

cooperation. Secondly, the low margins typically achieved in food ingredients 

and the relative inertia of well-established corporations are an 

effective deterrent to the development and implementation of novel technologies 

that could result in truly unique food products, whether for 

more effective production, food fortification, neutraceuticals, improved 

organoleptic properties, or development of novelty food products. However, 

the most important aspect of R&D, from the very first lab-bench 

tests, is an understanding of the industrial constraints and requirements 

to make a microencapsulation process viable, from the transition to 

full-scale production to the marketing of the final product. 

ACKNOWLEDGEMENT 

This study was supported by a grant of the Korea Health 21 R and D 

Project, Ministry of Health and Welfare, Republic of Korea (A050376). 

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