encapsulation review

Trends in Food Science & Technology 21 (2010) 510e523

Review

* Corresponding author.

0924-2244/$ - see front matter � 2010 Elsevier Ltd. All rights reserved.doi:10.1016/j.tifs.2010.08.003

Encapsulation of

polyphenols e

a review

Zhongxiang Fanga,b,* and
Bhesh Bhandaria
aSchool of Land, Crop and Food Sciences,

The University of Queensland, Brisbane,

Qld 4072, AustraliabSchool of Biosystems Engineering and Food Science,

Zhejiang University, Hangzhou 310029, China

(School of Land, Crop and Food Sciences, The

University of Queensland, Brisbane, Qld 4072,

Australia. Tel.: D61 7 33469187;

e-mail: [email protected])

Research on and the application of polyphenols, have recently

attracted great interest in the functional foods, nutraceutical and

pharmaceutical industries, due to their potential health benefits

to humans. However, the effectiveness of polyphenols depends

on preserving the stability, bioactivity and bioavailability of the

active ingredients. The unpleasant taste of most phenolic com-

pounds also limits their application. The utilization of encapsu-

lated polyphenols, instead of free compounds, can effectively

alleviate these deficiencies. The technologies of encapsulation

of polyphenols, including spray drying, coacervation, liposome

entrapment, inclusion complexation, cocrystallization, nanoen-

capsulation, freeze drying, yeast encapsulation and emulsion,

are discussed in this review. Current research, developments

and trends are also discussed.

IntroductionMicroencapsulation, developed approximately 60 years

ago, is defined as a technology of packaging solids, liquids,or gaseous materials in miniature, sealed capsules that canrelease their contents at controlled rates under specific con-ditions (Desai & Park, 2005; Vilstrup, 2001). The packagedmaterials can be pure materials or a mixture, which are alsocalled coated material, core material, actives, fill, internal

phase or payload. On the other hand, the packaging mate-rials are called coating material, wall material, capsule,membrane, carrier or shell, which can be made of sugars,gums, proteins, natural and modified polysaccharides,lipids and synthetic polymers (Gibbs, Kermasha, Alli, &Mulligan, 1999; Mozafari, 2006)

Microcapsules are small vesicles or particulates that mayrange from sub-micron to several millimeters in size(Dziezak, 1998). Many morphologies can be produced forencapsulation, but two major morphologies are more com-monly seen (Fig. 1): one is mononuclear capsules, whichhave a single core enveloped by a shell, while the otheris aggregates, which have many cores embedded in a matrix(Schrooyen, van der Meer, & De Kruif, 2001). Their spe-cific shapes in different systems are influenced by the pro-cess technologies, and by the core and wall materials fromwhich the capsules are made.

Various techniques are used for encapsulation. In gen-eral, three steps are involved in the encapsulation of bioac-tive agents: (i) the formation of the wall around the materialto be encapsulated; (ii) ensuring that undesired leakagedoes not occur; (iii) ensuring that undesired materials arekept out (Gibbs et al., 1999; Mozafari et al., 2008). Thecurrent encapsulation techniques include spray drying,spray cooling/chilling, extrusion, fluidized bed coating, co-acervation, liposome entrapment, inclusion complexation,centrifugal suspension separation, lyophilization, cocrystal-lization and emulsion, etc. (Augustin & Hemar, 2009;Desai & Park, 2005; Gibbs et al., 1999).

The main objective of encapsulation is to protect thecore material from adverse environmental conditions,such as undesirable effects of light, moisture, and oxygen,thereby contributing to an increase in the shelf life of theproduct, and promoting a controlled liberation of the encap-sulate (Shahidi & Han, 1993). In the food industry, themicroencapsulation process can be applied for a varietyof reasons, which have been summarized by Desai andPark (2005) as follows: (i) protection of the core materialfrom degradation by reducing its reactivity to its outside en-vironment; (ii) reduction of the evaporation or transfer rateof the core material to the outside environment; (iii) mod-ification of the physical characteristics of the original mate-rial to allow easier handling; (iv) tailoring the release of thecore material slowly over time, or at a particular time; (v) tomask an unwanted flavor or taste of the core material; (vi)dilution of the core material when only small amounts are

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http://dx.doi.org/10.1016/j.tifs.2010.08.003



Wall material

Core material

Wall material

Core material

Fig. 1. Two major forms of encapsulation: mononuclear capsule (left)and aggregate (right).

511Z. Fang, B. Bhandari / Trends in Food Science & Technology 21 (2010) 510e523

required, while achieving uniform dispersion in the hostmaterial; (vii) to help separate the components of the mix-ture that would otherwise react with one another. Food in-gredients of acidulants, flavoring agents, sweeteners,colorants, lipids, vitamins and minerals, enzymes andmicroorganisms, are encapsulated using different technolo-gies (Desai & Park, 2005).

Recently, research and application of polyphenols havebeen areas of great interest in the functional foods, nutra-ceutical and pharmaceutical industries (Manach, Scalbert,Morand, Remesy, & Jimenez, 2004; Scalbert, Manach,Morand, Remesy, & Jimenez, 2005). Polyphenols consti-tute one of the most numerous and ubiquitous groups ofplant metabolites, and are an integral part of both humanand animal diets which possess a high spectrum of biolog-ical activities, including antioxidant, anti-inflammatory, an-tibacterial, and antiviral functions (Bennick, 2002; Haslam,1996; Quideau & Feldman, 1996). A large body of preclin-ical research and epidemiological data suggests that plantpolyphenols can slow the progression of certain cancers, re-duce the risks of cardiovascular disease, neurodegenerativediseases, diabetes, or osteoporosis, suggesting that plantpolyphenols might act as potential chemopreventive andanti-cancer agents in humans (Arts & Hollman, 2005;Scalbert, Johnson, & Saltmarsh, 2005; Scalbert, Manachet al., 2005; Surh, 2003).

Unfortunately, the concentrations of polyphenols thatappear effective in vitro are often of an order of magnitudehigher than the levels measured in vivo. The effectivenessof nutraceutical products in preventing diseases dependson preserving the bioavailability of the active ingredients(Bell, 2001). This is a big challenge, as only a small propor-tion of the molecules remain available following oral ad-ministration, due to insufficient gastric residence time,low permeability and/or solubility within the gut, as wellas their instability under conditions encountered in foodprocessing and storage (temperature, oxygen, light), or inthe gastrointestinal tract (pH, enzymes, presence of othernutrients), all of which limit the activity and potentialhealth benefits of the nutraceutical components, includingpolyphenols (Bell, 2001). The delivery of these compoundstherefore requires product formulators and manufacturersto provide protective mechanisms that can maintain the ac-tive molecular form until the time of consumption, and de-liver this form to the physiological target within theorganism (Chen, Remondetto, & Subirade, 2006). Somephysicochemical characteristics and food properties of the

major polyphenols from different plant sources are presentin Table 1, which shows their limited stability and condi-tioned solubility. Another unfortunate trait of polypheonlsis their potential unpleasant taste, such as astringency(Table 1), which needs to be masked before incorporationinto food products (Haslam & Lilley, 1988).

The utilization of encapsulated polyphenols instead offree compounds can overcome the drawbacks of their insta-bility, alleviate unpleasant tastes or flavors, as well as im-prove the bioavailability and half-life of the compound invivo and in vitro. There have been a number of recent re-views or mini-reviews on the encapsulation of foods orfood ingredients (Augustin & Hemar, 2009; Desai &Park, 2005; de Vos, Faas, Spasojevic, & Sikkema, 2010;Flanagan & Singh, 2006; Gouin, 2004; Jafari, Assadpoor,He, & Bhandari, 2008; Khaled & Jagdish, 2007;McClements, Decker, Park, & Weiss, 2009; Mozafari,2005; Mozafari, 2006; Mozafari et al., 2008; Peter &Given, 2009). This review focuses on the encapsulationof the more widely used polyphenols, discussing theireffectiveness, variations, developments and trends.

Spray dryingSpray drying encapsulation has been used in the food in-

dustry since the late 1950s. Because spray drying is an eco-nomical, flexible, continuous operation, and producesparticles of good quality, it is the most widely used micro-encapsulation technique in the food industry and is typi-cally used for the preparation of dry, stable food additivesand flavors (Desai & Park, 2005). For encapsulation pur-poses, modified starch, maltodextrin, gum or other sub-stances are hydrated to be used as the wall materials. Thecore material for encapsulation is homogenized with thewall materials. The mixture is then fed into a spray dryerand atomized with a nozzle or spinning wheel. Water isevaporated by the hot air contacting the atomized material.The capsules are then collected after they fall to the bottomof the drier (Gibbs et al., 1999). The typical shape of spraydried particles is spherical, with a mean size range of10e100 mm (Fig. 2).

One limitation of the spray-drying technology is the lim-ited number of shell materials available, since the shell ma-terial must be soluble in water at an acceptable level (Desai& Park, 2005). Maltodextrins are widely used for encapsula-tion of flavours (Bhandari, 2007), which are also used forpolyphenol encapsulation. The ethanol extracts of black car-rots, which contain a high level of anthocyanins(125 � 17.22 mg/100 g), have been spray dried using malto-dextrins as a carrier and coating agents (Ersus & Yurdagel,2007). High air inlet temperatures (>160e180 �C) causedgreater anthocyanin losses, while the maltodextrin of20e21 DE gave the highest anthocyanin content powder atthe end of drying process (Ersus & Yurdagel, 2007). Themaltodextrin can also be mixed with gum arabic as wall ma-terial. A mixture of maltodextrin (60%) and gum arabic(40%) has been used for encapsulation of procyanidins

Table 1. Major polyphenols, sources and their properties.

Polyphenol groups Examples Sources Properties

Anthocyanidins Cyanidin, delphinidin, malvidin,pelargonidin, peonidin, petunidin andtheir glycosides.

Fruit, flowers Natural pigments; Highly sensitive to temperature,oxidation, pH, and lights; water soluble

Catechins Catechin, epicatechin, gallocatechin,epigallocatechin and epigallocatechingallate

Tea Sensitive to oxidation, lights and pH; astringentand bitter; slightly soluble in water

Flavanones Hesperetin, hesperidin, homoeriodictyol,naringenin, naringin

Citrus Sensitive to oxidation, lights and pH; aglyconesinsoluble but glycosides soluble in water

Flavones Apigenin, luteolin, tangeritin Fruit/vegetables Natural pigments; sensitive to oxidation and pH;aglycones slightly soluble but glycosides soluble in water

Flavonols Kaempferol, myricetin, quercetin andtheir glycosides

Fruit/vegetables Sensitive to oxidation, lights and pH; aglycones slightlysoluble but glycosides soluble in water

Isoflavones Daidzein, genistein, glycitein Soybeans,peanuts

Sensitive to alkaline pH; astringent and bitter; soy smell;water soluble

Hydroxybenzoicacids

Gallic acid, p-hydroxybenzoic,vanillic acid

Berries, tea,wheat

Sensitive to temperature, oxidation, pH, and lights; mostsoluble in water

Hydroxycinnamicacids

Caffeic acid, ferulic acid, p-coumaricacid, sinapic acid

Fruit, oats, rice Sensitive to oxidation and pH; Most slightly solublein water

Lignans Pinoresinol, podophyllotoxin,steganacin.

Flax, sesame,vegetables

Relatively stable under normal conditions; unpleasantflavour; water soluble.

Tannins(proanthocyanidines)

Castalin, pentagalloyl glucose,procyanidins

Tea, berries,wines,chocolate

Sensitive to high temperature and oxidation; astringentand bitter; water soluble

512 Z. Fang, B. Bhandari / Trends in Food Science & Technology 21 (2010) 510e523

from grape seeds (Zhang, Mou, & Du, 2007). The ratio ofcore substance to wall material was 30:70 w/w, while theconcentration of the slurry was 20% w/v. The encapsulationefficiency was up to 88.84%, and the procyanidin was notchanged during drying. The stability of the products was ob-viously improved by spray drying.

Chitosan has also been used as a wall material in spraydrying of olive leaf extract (OLE) (Kosaraju, D’ath, &Lawrence, 2006). The loading percent of polyphenoliccompounds was 27%, and the OLE-loaded microspheresnormally had a smooth surface morphology. The FTIRspectroscopy results indicated that the majority of theOLE in the chitosan microsphere were physically encapsu-lated in the chitosan matrix. Chiou and Langrish (2007) in-troduced citrus fruit fiber as an encapsulating agent forspray drying of bioactives extracted from Hibiscus sabdar-iffa L. The main bioactive compounds in H. sabdariffa L.extract are polyphenols, or more specifically, the anthocya-nin complexes. The presence of the bioactive material inthe fibers did not appear to significantly affect the productsize or shape. The results demonstrated that natural fruitfibers might be a potential replacement carrier for spraydrying sticky materials. This encapsulation process com-bined two products (fruit fiber and polyphenols) into onemultipurpose functional food, creating a novel nutraceuticalproduct suitable for a variety of applications in functionalfood manufacturing (Chiou & Langrish, 2007).

More recently, the effects of drying aids comprising col-loidal silicon dioxide (tixosil 333), maltodextrin and starchon spray drying of soybean extract have been studied(Georgetti, Casagrande, Souza, Oliveira, & Fonseca,2008). The resulting product, to which was added tixosil

333, showed a lower degradation of its polyphenol contentand lower reduction of its antioxidant activity, suggestingthat the correct selection of the drying excipients is an im-portant step in guaranteeing the stability and the quality ofthe finished product. The results also indicated that the inletgas temperature had a significant effect on the total poly-phenol, protein and genistein contents of the dried extracts(Georgetti et al., 2008). Another wall material successfullyused for encapsulation of polyphenol was protein-lipid (so-dium caseinate-soy lecithin) emulsion, which has been usedin spray drying of grape seed extract, apple polyphenol ex-tract and olive leaf extract (Kosaraju, Labbett, Emin,Konczak, & Lundin, 2008). Optical microscopy and parti-cle size distribution analysis indicated that the encapsulatedparticles all had spherical morphology and uniform sizedistribution. Radical scavenging activity studies demon-strated a significant retention of antioxidant activity afterencapsulation by the spray-drying process (Kosarajuet al., 2008).

CoacervationThe concept behind coacervation microencapsulation is

the phase separation of one or many hydrocolloids fromthe initial solution and the subsequent deposition of thenewly formed coacervate phase around the active ingredi-ent suspended or emulsified in the same reaction media(Gouin, 2004). Coacervation encapsulation can be achievedsimply with only one colloidal solute such as gelatin, orthrough a more complex process, for example, with gelatinand gum acacia. Complex coacervation is usually associ-ated with no definite forms (Fig. 2), and is considered anexpensive method for encapsulating food ingredients

Fig. 2. Illustration of the characteristics of encapsulated polyphenolic capsules produced by various encapsulation processes.


(Gouin, 2004); however, this process should be related tothe potential benefits it might offer, especially to high-value, labile functional ingredients, such as the encapsula-tion of polyphenols.

Yerba mate (Ilex paraguariensis) extract (containing62.11 � 1.16 mg of gallic acid/g yerba mate) has been en-capsulated with two different systems: calcium alginate andcalcium alginate-chitosan (Deladino, Anbinder, Navarro,&Martino, 2008). A high load of active compound (>85%)was obtained in the alginate beads but in chitosan coatedbeads the entrapment was lower (around 50%), on accountof the active compound being lost during immersion in

chitosan. The polyphenols can be retained in a chitosan-al-ginate membrane, but maximum release in water wasachieved in a shorter time for chitosan coated beads thanwith the alginate beads. These results implied that thewall materials can affect the release of the natural antioxi-dants of yerba mate.

Gelatin is a protein containing many glycine, proline and4-hydroxyproline residues. A new type of protein/polyphe-nol microcapsule based on (�)-epigallocatechin gallate(EGCG) and gelatin (type A), has been produced usingthe layer-by-layer (LbL) assembly method (Shutava,Balkundi, & Lvov, 2009). The first layer was a gelatin layer


over the MnCO3 microcores, over which an EGCG layerwas formed by adding EGCG solution to the gelatin-coatedmicroparticles. The MnCO3 microcores were dissolved inEDTA solution to form the stable (Gel A/EGCG)4 capsules.The EGCG content of the protein/polyphenol film materialwas as high as 30% w/w, while the EGCG in the LbL as-semblies retained its antioxidant activity (Shutava,Balkundi & Lvov, 2009).

Glucan is a polysaccharide, and also a thermoreversiblegelling agent, whose gelling behavior depends on its molec-ular weight and concentration (Vaikousi, Biliaderis, &Izydorczyk, 2004). During cooling of the glucan water so-lution from 80 �C to room temperature, a network structurecan be formed through an interaction of the chain segmentassociation and aggregated junction zones (Morgan &Ofman, 1998). Black currant extract has been encapsulatedin glucan by simply mixing with hot dispersed glucan gel,followed by cooling and cutting into cubes, or being drop-ped into oil to produce a bead morphology (Xiong, Melton,Easteal, & Siew, 2006). Recovery of 73e79% of encapsu-lated anthocyanins was achieved using normal oven dryingto dehydrate the gel matrix. Larger amounts of anthocya-nins were released from cubes than from beads using thesame drying process. The encapsulated anthocyanins ex-hibited little difference as free radical scavengers, with anincrease in their reducing ability with time.

Other coacervation coating systems such as gliadin, hep-arin/gelatin, carrageenan, soy protein, polyvinyl alcohol,gelatin/carboxymethylcellulose, b-lactoglobulin/gum aca-cia, and guar gum/dextran have also been studied (Gouin,2004). However, most of the core materials in these studieswere essential oils rather than polyphenols.

LiposomesLiposomes were first described by Bangham and co-

workers in 1965 at Cambridge University (Bangham,Standish, &Watkins, 1965). They are colloidal particles con-sisting of a membranous system formed by lipid bilayers en-capsulating aqueous space(s) (Fig. 2). Owing to thepossession of both lipid and aqueous phases, liposomescan be utilized in the entrapment, delivery, and release of wa-ter soluble, lipid-soluble, and amphiphilic materials. The un-derlying mechanism for the formation of liposomes andnanoliposomes is basically a hydrophilicehydrophobic in-teraction between phospholipids andwater molecules. Ama-jor advantage of their use is the ability to control the releaserate of the incorporated materials and deliver them to theright place at the right time (Schafer et al., 1992). Bioactiveagents encapsulated into liposomes can be protected from di-gestion in the stomach, and show significant levels of absorp-tion in the gastrointestinal tract, leading to the enhancementof bioactivity and bioavailability (Takahashi et al., 2007).

There are several methods for producing liposomes, andthere are a number of excellent books and published re-views that provide details of the most common productiontechniques (Betageri & Kulkarni, 1999; Frezard, 1999;

Mozafari & Mortazavi, 2005; Mozafari et al., 2008;Watwe & Bellare, 1995). A variety of liposome techniqueshave been employed for the encapsulation of polyphenols.

Fan, Xu, Xia, and Zhang (2007) compared the effects offive different liposome methods on the encapsulation of sal-idroside e thin film evaporation, sonication, reverse phaseevaporation, melting, and freezing-thawing. Multilamellarvesicles can be obtained by thin film evaporation, largerunilamellar vesicles by reverse phase evaporation, andsmall unilamellar vesicles by sonication or extrusion tech-nique (Bangham et al., 1965; Cevce, 1993.). The freez-ing-thawing treatment leads to the production of specialfreezing-thawing multilamellar vesicles (Maestrelli,Gonzalez-Rodriguez, Rabasco, & Mura, 2006). The encap-sulating efficiency of liposomes is highest when they areprepared by freezing-thawing, followed by thin film evapo-ration, then reverse phase evaporation, while melting andsonication has the lowest efficiency. Loading capacity ofsalidroside can have significant effects on encapsulatingefficiency, average diameter, and z potential of liposomes.Liposomal systems prepared by sonication, melting, and re-verse phase evaporation, displayed better dispersivity. Sali-droside liposomes show a slower increase in particle sizethan liposomes without salidroside, suggesting salidrosideplays an important role in preventing the aggregation andfusion of liposomes. Fan et al. (2007) illustrated that thesedifferences might come from the different morphologies ofliposomes prepared by different methods.

The nature of the core materials is another factor that af-fects the efficiency of liposome encapsulation. The isomersof (þ)-catechin and (�)-epicatechin entrapped in lipo-somes show similar encapsulation levels and release rates(Fang, Hwang, Huang, & Fang, 2006). However, anothertype of catechin, (�)-epigallocatechin-3-gallate (EGCG),has been observed to have a much higher level of encapsu-lation for the same liposome system. EGCG contains a gal-loyl group, indicating a greater lipophilicity. Hence it ispossible that EGCG was stronger when to locate withinthe liposome bilayers, thereby increasing the entrapment.

Liposome encapsulation efficiency can be increased bythe addition of ethanol (15%) to the preparation hydrationsolution (Fang, Lee, Shen, & Huang, 2006). In response,the core material of EGCG in the liposomes showeda high rate of encapsulation of nearly 100%, compared to84.6% encapsulation for conventional liposome. It wasalso shown that ethanolic solutions of phospholipids exhibithigh encapsulation efficiency for both hydrophilic and lipo-philic actives (Dayan & Touitou, 2000). The liposomesmade in the presence of ethanol had a relatively smallsize of 133.1 nm. The further addition of deoxycholicacid (DA) significantly increased the size of the vesiclesto 378.2 nm. EGCG encapsulated in liposomes with ethanoland DA gave a 20 fold increase in active deposition in basalcell carcinomas relative to the free form (Fang et al., 2006).The larger vesicle size of this formulation was suggested tobe the predominant factor governing this enhancement.


Evidence of liposomes enhancing the bioactivity andbioavailability of polyphenols has been reported by a num-ber of researchers. Curcumin [1,7-bis (4-hydroxy-3-me-thoxyphenyl)-1,6-hepadiene-3,5-dion] is the principlecurcuminoid of the popular India spice turmeric, which ex-hibits anti-HIV, antitumor, antioxidant, and anti-inflamma-tory activities (Maheshwari, Singh, Gaddipati, & Srimal,2006). However, curcumin is poorly absorbed from the gas-trointestinal (GI) tract after oral administration, due to itslow water solubility and low stability against GI fluidsand/or alkaline/higher pH conditions. To enhance the bio-availability and food functionality of curcumin, liposome-encapsulated curcumin (LEC) can be prepared from com-mercially available lecithins (SLP-PC70) and curcumin,by using a microfluidizer (Takahashi, Uechi, Takara,Asikin, & Wada, 2009). The resulting LEC is composedof small unilamellar vesicles with a diameter of approxi-mately 263 nm, with encapsulation efficiency for curcuminof 68.0%. A faster rate and better absorption were observedfor LEC relative to other forms. The results indicated thatcurcumin enhanced the gastrointestinal absorption by lipo-some encapsulation, while the plasma antioxidant activityfollowing oral LEC was significantly higher than that ofother treatments. Another example reported was quercetinliposomes prepared from egg phosphatidylcholine/choles-terol (2:1) (Priprem, Watanatorn, Sutthiparinyanont,Phachonpai, & Muchimapura, 2008). The resulting lipo-somes were approximately 200 nm in mean particle diam-eter with a negative surface charge and a range ofencapsulation efficiency between 60% and 80%. Both con-ventional and quercetin liposomes have shown anxiolyticand cognitive-enhancing effects. A lower dose (20 mg/kgbody weight day) and a faster rate of absorption were ob-served with intranasal quercetin liposomes when comparedwith oral quercetin (300 mg/kg body weight/day). The re-sults suggested that intranasal delivery of quercetin in theform of liposomes to the brain could allow a reduction inthe dose and thereby reduce the potential of toxicity ofthe quercetin (Priprem et al., 2008).

A modified liposome system encapsulating of resveratrolhas been developed, with the encapsulated particles beingcalled “acoustically active lipospheres” (AALs) or “microbub-bles” (Fang et al., 2007). The liposome is prepared using dis-solved soybean phosphatidylcholine, cholesterol, co-emulsifier, and resveratrol in chloroformemethanol. Afterevaporation of the organic solvent and rehydration, AALsare formed by stabilization using coconut oil and perfluorocar-bons. The benefits of AALs are high core material loading ca-pacity (>90%) with a small droplet size (mean diameter ofw300 nm), together an acceptable level of safety, sustainedcore material release, and high sensitivity to ultrasound treat-ment. The ultrasound sensitivity of AALs is very useful, asthey possess the potential to be “magic bullet” agents forthe delivery of core materials to precise locations in thebody, with the locations being determined by focusing the ul-trasound energy.

Inclusion encapsulationMolecular inclusion is generally achieved by using cy-

clodextrins (CDs) as the encapsulating materials. CDs area group of naturally occurring cyclic oligosaccharides de-rived from starch, with six, seven or eight glucose residueslinked by a (1-4) glycosidic bonds in a cylinder-shapedstructure, and denominated as a-, b- and g-cyclodextrins,in which b- cyclodextrin is commonly applied(Pagington, 1986.) The external part of the cyclodextrinmolecules is hydrophilic, whereas the internal part is hy-drophobic (Fig. 2). This structure characteristic makesCDs a satisfactory medium for encapsulation of less polarmolecules (such as essential oils) into the apolar internalcavity through a hydrophobic interaction (Bhandari,D’Arcy, & Padukka, 1999; Dziezak, 1998).

One outstanding advantage of the inclusion of polyphe-nols in CDs is the effect in improving their water solubility,especially for the less water soluble phytochemicals. Theinclusion of hesperetin and hesperidin in (2-hydroxy-propyl)-b-cyclodextrin (HP-b-CD) (Tommasini et al.,2005), resveratrol in b-CD and maltosyl-b-CDs (Lucas-Abellan, Fortea, Lopez-Nicolas, & Nunez-Delicado, 2007),olive leaf extract (rich in oleuropein) in b-CD (Mourtzinos,Salta, Yannakopoulou, Chiou, & Karathanos, 2007), querce-tin and myricetin in HP-b-CD, maltosyl-b-CDs and b-CDs,(Lucas-Abellan, Fortea, Gabaldon, & Nunez eDelicado,2008), kaempferol, quercetin and myricetin in HP-b-CD(Mercader-Ros, Lucas-Abellan, Fortea, Gabaldon, &Nunez-Delicado, 2010), 3-hydroxyflavone (3-OHeF),morin and quercetin in a- and b-CDs (Calabro et al.,2004), rutin in b-CD (Ding, Chao, Zhang, Shuang, & Pan,2003) have been studied, and their water solubilities im-proved by inclusion encapsulation. In addition, their antiox-idant activities all increased in these CDs encapsulatedsystems. The improved antioxidant efficacy of the inclusioncomplex may come from the protection of the polyphenolsagainst rapid oxidation by free radicals (Mercader-Roset al., 2010), which may in part be explained by an increasein their solubility in the biological moiety (Ding et al., 2003).

The encapsulation efficacy of CDs inclusion is affectedby the core materials. Generally, the higher the hydropho-bicity and smaller the molecule is, the greater the affinityfor the CDs. For example, based on their relative CDs affin-ity, hesperetin was more effective than hesperidin(Tommasini et al., 2005), and 3-OHeF was more effectivethan morin or quercetin (Calabro et al., 2004). On the otherhand, different wall materials affect the encapsulation ca-pacity for the same core material. For example, a numberof studies have been reported on the encapsulation of cur-cumin in different CD variants (Tang, Ma, Wang, &Zhang, 2002; Tomren, Masson, Loftsson, & Tonnesen,2007; Tonnesen, Masson, & Loftsson, 2002). It has beenshown that HP-b-CD has the highest encapsulation capacityfor curcumin (Tomren et al., 2007). For the core materialsof quercetin and myricetin, the affinity to CDs was HP-b-CD > maltosyl-b-CDs > b-CDs, reflecting the greater


affinity of modified cyclodextrins (Lucas-Abellan, Fortea,& Gabaldon, 2008)

To illustrate the structures of polyphenol-CD inclusioncomplexes, some advanced analytical instruments were ap-plied. The spatial configuration of the complex of rutin withb-CD has been proposed, based on NMR andmolecular mod-eling (Ding et al., 2003), which revealed that the binding sitefor rutin is a single ring of rutin molecule penetrating into theb-CD cavity in the shallow position, forming a 1:1 inclusioncomplex. This structure can be confirmed by 1HNMRand cir-cular dichroism spectroscopy (Calabro et al., 2005).The struc-ture of the inclusion complex of ferulic acid (FA) with a-CDhas been analyzed by rotating frame nuclear overhouser effectspectroscopy (ROESY) (Anselmi et al., 2008). Based on thistechnology and modeling simulation, the insertion of the FAinto the lipophilic interior of a-CD involves the -COOH anda, b-unsaturated groups and part of its aromatic moiety. Thephenol andmethoxyl groups ofFA lie on the plane of thewiderrim. This encapsulation increases the photo-stability of FA,slows FA release, and would provide safer and longer-lastingprotection of the skin against solar radiation, if applied in cos-metic formulations (Anselmi et al., 2008)

With the exception of CDs, other types of biopolymershave been employed in the molecular inclusion of polyphe-nols, such as curcumin being encapsulated in hydrophobi-cally modified starch (HMS) (Yu & Huang, 2010). Thecomplexed curcumin showed a 1670 fold increase in solu-bility, possibly reflecting the hydrophobic interaction andhydrogen bonding between curcumin and HMS. The encap-sulated curcumin revealed enhanced in vitro anti-cancer ac-tivity compared to the free form.

CocrystallizationCo-crystallization is an encapsulation process in which the

crystalline structure of sucrose is modified from a perfect to anirregular agglomerated crystal, to provide a porous matrix inwhich a second active ingredient can be incorporated (Chen,Veiga, & Rizzuto, 1988). Spontaneous crystallization of super-saturated sucrose syrup is achieved at high temperature (above120 �C) and low moisture (95e97 �Brix). If a second ingredi-ent is added at the same time, the spontaneous crystallizationresults in the incorporation of the second ingredient into thevoid spaces inside the agglomerates of the microsized crystals(Fig. 2), with a size less than 30 mm (Bhandari, Datta, D’Arcy,& Rintoul, 1998). The main advantages of cocrystallizationare improved solubility, wettability, homogeneity, dispersibil-ity, hydration, anticaking, stability and flowability of the en-capsulated materials (Beristain, Vazquez, Garcıa, & Vernon-Carter, 1996). Other advantages are that the core materialsin a liquid form can be converted to a dry powdered formwithout additional drying, and the products offer direct tablet-ing characteristics because of their agglomerated structure,and thus offer significant advantages to the candy and pharma-ceutical industries (Desai & Park, 2005).

Deladino, Anbinder, Navarro, and Martino (2007) re-ported on the encapsulation of yerbamate (I. paraguariensis)

extract containing caffeoyl derivatives and flavonoids, bycocrystallization in a supersaturated sucrose solution. Theco-crystallized product had a typically cluster-like agglom-erate structure with void spaces and a sucrose crystal sizevarying between 2 and 30 mm. An extra layer of a networkwith neat edges covered the crystals. The microstructurewas further confirmed by differential scanning calorimetry,X-ray diffraction and scanning electron microscopy(Deladino, Navarro, &Martino, 2010). The cocrystallizationof yerba mate extract changed it from a cohesive material tobe a non-cohesive product, and notably reduced its hygro-scopic characteristics without affecting its high solubility;this demonstrated that cocrystallization is a good alternativefor the preservation and handling of yerba mate extract forfurther application in food products. There have been veryfew reports of the application of the cocrystallizationprocess.

NanoencapsulationNanoencapsulation involves the formation of active-

loaded particles with diameters ranging from 1 to1000 nm (Reis, Neufeld, Ribeiro, & Veiga, 2006). Theterm nanoparticle is a collective name for both nano-spheres and nanocapsules. Nanospheres have a matrixtype of structure. Actives may be absorbed at the spheresurface or encapsulated within the particle. Nanocapsulesare vesicular systems in which the active is confined toa cavity consisting of an inner liquid core surrounded bya polymeric membrane (Fig. 2) (Couvreur, Dubernet, &Puisieux, 1995). The active substances are usually dis-solved in the inner core but may also be adsorbed to thecapsule surface (Allemann, Gurny, & Doekler, 1993). Itis proposed that any target actives, while incorporatedinto a complex of polymers, which result in nanoscale-sized particles, might be called ‘encapsulated nanopar-ticles’. Compared to micron-sized particles, nanoparticlesprovide a greater surface area and have the potential to in-crease solubility due to a combination of large interfacialadsorption of the core compound, enhanced bioavailabil-ity, improved controlled release, which enable better pre-cision targeting of the encapsulated materials (Mozafariet al., 2008). A variety of techniques have been employedto develop polyphenol nanoparticles.

Barras et al. (2009) describe the loading of quercetin andEGCG by lipid nanocapsules (LNC) through the applica-tion of the phase inversion process. Briefly, the activeswere mixed in the oil phase prior to preparation. Soybeanlecithin, surfactant, NaCl and distilled water were thenmixed and heated to form a W/O emulsion. The mixturewas cooled, and distilled cold water (0 �C) added, with stir-ring to form O/W nanocapsules. The benefits of this methodare that the average volume sizes of particles are a functionof the formulation composition, which means the LNC sizecan be tailored by formulation design. The higher encapsu-lated quercetin LNC increased its apparent aqueous solubil-ity by a factor of 100. The encapsulated quercetin and


(�)-EGCG have proved to be more stable compared to thefree ones.

The nanoprecipitation technique has been used for cur-cumin entrapment, based on poly (lactide-co-glycolide)(PLGA) and a stabilizer polyethylene glycol (PEG)-5000(Anand et al., 2010). The nanoprecipitation technique in-volves three steps: First, the target actives and a polymerare mixed in an organic solution; second, the mixture isadded, drop wise, to an aqueous solution, normally contain-ing a surfactant; third, the resulting dispersion of nanopar-ticles is vacuum evaporated to eliminate the organicsolvent, and then centrifuged or filtered to obtain the parti-cles. In the case of curcumin-loaded nanoparticles, the en-capsulation efficiency was reported to have reached 97.5%,with the particle diameter being about 80.9 nm, which en-hanced its cellular uptake, and increased in vitro bioactivity,resulting in superior in vivo bioavailability over free curcu-min (Anand et al., 2010). Other quercetin loaded nanopar-ticles were developed by using a similar technique, witha particle size of <85 nm, and encapsulation efficiency ofover 99% (Wu et al., 2008). The encapsulated active ofquercetin might have an amorphous state, which formed in-termolecular hydrogen bonding with carriers. The releaseof the nanoparticals was 74-fold times higher when com-pared with the pure active, and possessed more effective an-tioxidant activities.

A method based on the concept of emul-sionediffusioneevaporation, using polyethylene glycol(PEG) 400 as a co-solvent, has been applied on ellagicacid (EA) loaded PLGA nanoparticles (Bala, Bhardwaj,Hariharan, Kharade, Roy, & Ravi Kumar, 2006). Didode-cyldimethylammomium bromide (DMAB) and polyvinylalcohol (PVA), alone and in combination with chitosan(CS), were used as the stabilizer. The basis of this techniqueis as follows: the stirring of the EA-PLGA-PEG 400 mix-ture causes the dispersion of the solvent in the form of ir-regularly sized droplets in equilibrium with thecontinuous phase, while the stabilizer is adsorbed on tothe larger interface, thereby creating the first emulsionstage; then, the homogenization results in smaller dropletswith more homogenous size distribution; the addition ofwater and subsequent heating destabilizes the equilibriumand causes the organic solvent to diffuse into the aqueousphase and then out of the system, leading to precipitationof the polymer along with the active as very small particles(Kumar, Bakowsky, & Lehr, 2004). The initial release ofEA from nanoparticles in pH 7.4 phosphate buffer is rapid,followed by a slower sustained release. An in situ intestinalpermeability study in rats showed a higher uptake of activeencapsulated in nanoparticles prepared using PVA,PVAeCS blend and DMAB as stabilizers, than pure active(Bala et al., 2006).

Resveratrol is incorporated into amphiphilic copolymersof mPEGePCL (methoxy poly(ethylene glycol)-poly(cap-rolactone)), with an active loading content of19.4 � 2.4% and an encapsulation efficiency of >90%

(Shao et al., 2009). The mPEGePCL based nanoparticlesare composed of a hydrophilic segment and a hydrophobicsegment, which are capable of loading the target active byself assembling into nanoscale spherical structures witha hydrophilic outer shell and a hydrophobic inner core(Liu et al., 2008). In this way, lipophilic actives can be en-trapped into the hydrophobic core of the nanosphere, whileits hydrophilic outer shell is maintained as a stabilizer forthe system. Other actives with lipophilicity can also be in-corporated into this nanoparticle system to enhance theirbioavailability.

Tea catechins have been successfully encapsulated in chi-tosan- tripolyphosphate (CS-TPP) nanoparticles using a sim-ple ionotropic gelation method (Hu et al., 2008). Bycontrolling the critical fabricating parameters of the CS mo-lecular mass, CS concentration, and CS-TPP mass ratio, de-sirable CS-TPP nanoparticles can be spontaneously formedwhen the freshly prepared CS solution containing tea cate-chins is added with TPP solution, while stirring at room tem-perature (Hu et al., 2008). In comparison with this simplemethod, a relatively complicated method has been developedfor the encapsulation of polyphenols of EGCG, tannic acid,curcumin, and theaflavin (Shutava, Balkundi, Vangala et al.,2009). First, gelatin nanoparticles are prepared using a two-step desolvation method. These particles are then furtherencapsulated in polyelectrolytes using a layer-by-layer shellassembly method. Finally, the polyphenols are loaded intothe prepared nanoparticles by adsorption under certain pHvalues. The adsorption of polyphenols to the nanoparticlesdepends on the chemical nature of the molecules. Adsorptionof polyphenols with higher molecular weights and a largernumber of phenolic -OH groups was found to be higher.The amount of theaflavin, the polyphenol with the highestmolecular weight among those investigated, was as high as70% of the mass of nanoparticle solid material. Loading oftannic acid and EGCG is lower, while it is almost negligiblefor curcumin (Shutava, Balkundi, Vangala et al., 2009).

Freeze dryingFreeze drying, also known as lyophilization or cryode-

siccation, is a process used for the dehydration of almostall heat-sensitive materials and aromas. Freeze-dryingworks by freezing the material and then reducing the sur-rounding pressure and adding enough heat, to allow the fro-zen water in the material to sublimate directly from thesolid phase to the gas phase (Oetjen & Haseley, 2004). En-capsulation by freeze drying is achieved as the corematerials homogenize in matrix solutions and then co-ly-ophilize, usually resulting in uncertain forms (Fig. 2).Except for the long dehydration period required (generally20 h), freeze-drying is a simple technique for encapsulatingwater-soluble essences and natural aromas, as well as drugs(Desai & Park, 2005). Freeze dried samples of pomace con-taining anthocyanin and maltodextrin DE20 have showngood shelf life stability during storage at 50 �C/0.5 wateractivity for up to two months (Delgado-Vargas, Jimenez,


& Pardes-Lopez, 2000). Recently, Laine, Kylli, Heinonen,and Jouppila (2008) encapsulated phenolic-rich cloudberryextract by freeze drying, using maltodextrins DE5-8 andDE18.5 as wall materials. The microencapsulated cloud-berry extract offered better protection for phenolics duringstorage, while the antioxidant activity remained the same oreven improved slightly.

However, there is also some evidence of freeze dryinginduced encapsulation being unable to improve stabilityor bioactivity. When Hibisus anthocyanin extract was en-capsulated in pullulan by freeze drying, it was only whensamples stored at higher relative humidity levels(aw>0.75) that the free anthocyanins showed w1.5e1.8times faster degradation than the pullulan-anthocyanin co-lyophilized materials (Gradinaru, Biliaderis, Kallithraka,Kefalas, & Garcia-Viguera, 2003). Obviously, this wasnot a big difference. Furthermore, both free and co-lyophi-lized with pullulan, Hibiscus anthocyanins exhibited goodantiradical activity throughout storage, and no significantdifferences were observed between them, suggesting thatthe encapsulation might not be necessary if the Hibisus an-thocyanin extract is to be freeze dried.

Yeast encapsulationEncapsulation of essential oils and flavours by using yeast

cells (Saccharomyces cerevisiae) as wall material haveproven to to be a low cost, high volume process (Bishop,Nelson, & Lamb, 1998). Yeast encapsulation depends onthe yeast cells, which allow the actives to pass freely throughthe cell wall and membrane, while remaining passivelywithin the cells (Fig. 2). Encapsulation by yeast cells cancontrol the diffusion of actives through the cell wall andmembrane, using a defined temperature and time, ina pre-determined solutionmix, with thewall of the yeast cellsproviding protection of the liquid active ingredients againstevaporation, extrusion, oxidation and light (MICAP PLC,2004).This technology has been typically used for encapsu-lation of small lipophilic molecules such as essential oils.

The yeast cells have proved to be able to absorb and re-tain water-soluble flavor compounds when pre-treated witha plasmolyser (Serozym Laboratories, 1973). This tech-nique has been adopted in water soluble polyphenol encap-sulation. After treatment with 5% sodium chloride at 54 �Cfor 24 h for autolysis, the yeast cells can be used to encap-sulate water soluble polyphenol of chlorogenic acid, withan encapsulation efficiency of 12.6% (Shi et al., 2007).The yeast encapsulated chlorogenic acid was found to behighly stable under wet and thermal stresses, with the re-lease profiles suggesting that the yeast cells could preventchlorogenic acid from change, without significantly slow-ing down the release. Another obvious benefit of this tech-nique is that no additives apart from water, yeast and corematerials are used during processing, thereby ensuring itssafety in the food industries (Blanquet et al., 2005).

EmulsionsEmulsion technology is generally applied for the encapsu-

lation of bioactives in aqueous solutions, which can either beused directly in the liquid state or can be dried to formpowders(e.g., by spray, roller, or freeze drying) after emulsification.Therefore it is actually a part of encapsulation process. Basi-cally, an emulsion consists of at least two immiscible liquids,usually as oil and water, with one of the liquids being dis-persed as small spherical droplets in the other (Friberg,Larsson, & Sjoblom, 2004; McClements, 2005). Typically,the diameters of the droplets in food systems range from 0.1to100 mm (McClements et al., 2009). Emulsions can be clas-sified according to the spatial organization of the oil and waterphases. A system that consists of oil droplets dispersed in anaqueous phase is called an oil-in-water (O/W) emulsion,whereas a system that consists of water droplets dispersedin an oil phase is called a water-in-oil (W/O) emulsion(Fig. 2). With the exception of the simple O/W or W/O sys-tems, various types of multiple emulsions can be developed,such as oil-in-water-in-oil (O/W/O) or water-in-oil-in-water(W/O/W) emulsions (Benichou, Aserin, & Garti, 2004; vander Graaf, Schroen, & Boom, 2005). To obtain a kineticallystable solution, stabilizers such as emulsifiers or texture mod-ifiers, are commonly added in the emulsion systems. The useof this technology for delivering food components and nutri-ceuticals has been comprehensively reviewed by Augustinand Hemar (2009), Flanagan and Singh (2006) andMcClements et al. (2009).

A US patent named “functional emulsions”, relates todissolved polyphenols in ethanol (polyglycerol oleic acidester added), which are then stirred with vegetableoil in a homogenizer, or emulsified, to obtain E/O type orE/O/W type emulsions (Nakajima, Nabetani, Ichikawa, &Xu, 2003). These emulsions can be used in pharmaceutical,nutriceutical or food industries as polyphenol delivery sys-tems. Naturally these polyphenols are insoluble or have lowsolubility in water and oil, so the obvious advantage ofthese emulsions is that they contain a high concentrationof polyphenols. Most recent researches in relation to poly-phenol emulsions have been used for the reduction of lipidoxidation or increase lipid stability. In one study, after dis-solving Tween 20 in water containing lyophilized tea infu-sion and bovine serum albumin (BSA), sunflower oil (fromwhich tocopherols has been removed) was added dropwiseto the aqueous sample in an ice bath and sonicated for5 min (Almajano, Carbo, Jimenez, & Gordon, 2008). TheW/O emulsions containing tea extracts have shown strongantioxidant activity against oil oxidation. Another W/Oemulsion prepared by the same research group using a sim-ilar method but containing caffeic acid as an antioxidantand Fe (III) as a pro-oxidant ion, also noted the antioxidantactivity of caffeic acid (Almajano, Carbo, Delgado, &Gordon, 2007). However, when different polyphenolswere used in the W/O emulsions, their antioxidant activitiesshowed different characteristics. In the Tween 20-phos-phate buffer-olive oil emulsion system, gallic acid can

Table 2. Technologies for encapsulation of polyphenols.

Encapsulation Technologies Polyphenols References

Spray DryingWall materials:Maltodextrins black carrot extracts (anthocyanins) Ersus & Yurdagel, 2007Maltodextrin and gum arabic procyanidins Zhang et al., 2007Chitosan olive leaf extract Kosaraju et al., 2006Citris fruit fiber Hibiscus sabdariffa L. extract

(anthocyanins)Chiou & Langrish, 2007

Colloidal silicon dioxide, maltodextrin and starch soybean extract Georgetti et al., 2008Sodium caseinate-soy lecithin grape seed extract, apple polyphenol

extract and olive leaf extractKosaraju et al., 2008

CoacervationWall materials:Calcium alginate and calcium alginateechitosan yerba mate extract Deladino, Anbinder, Navarro, &

Martino, 2008Gelatin (type A) EGCG Shutava et al., 2009aGlucan black currant extract Xiong et al., 2006

LiposomeSpecific methods:Thin film evaporation, sonication, reverse phase

evaporation, melting, and freezing-thawingsalidroside Fan et al., 2007

Thin film evaporation (þ)-catechin, (�)-epicatechin, EGCG Fang, Hwang, Huang, & Fang C.-C, 2006aUsing microfluidizer curcumin Takahashi et al., 2009Lipid thin film formation and extrusion quercetin Priprem et al., 2008Thin film evaporation and sonication resveratrol Fan et al., 2007

Inclusion encapsulationWall materials:HP-b-CD hesperetin and hesperidin Tommasini et al., 2005b-CD and maltosyl-b-CDs resveratrol Lucas-Abellan et al., 2007b-CD olive leaf extract (rich in oleuropein) Mourtzinos et al., 2007HP-b-CD, maltosyl-b-CDs and b-CDs quercetin and myricetin Lucas-Abellan et al., 2008HP-b-CD kaempferol, quercetin and myricetin Mercader-Ros et al., 2010a- and b-CDs 3-hydroxyflavone, morin and quercetin Calabro et al., 2004b-CD rutin Ding et al., 2003HP- b-CD curcumin Tomren et al., 2007HP- b-CD, maltosyl-b-CDs, b-CDs, quercetin and myricetin Lucas-Abellan et al., 2008b-CD rutin Ding et al., 2003a-CD ferulic acid Anselmi et al., 2008hydrophobically modified starch curcumin Yu & Huang, 2010

CocrystallizationYerba mate extract Deladino et al., 2007

Freeze dryingWall materials:Maltodextrin DE20 anthocyanin Delgado-Vargas et al., 2000Maltodextrins DE 5-8 and DE18.5 cloudberry extract Laine et al., 2008Pullulan Hibisus anthocyanin Gradinaru et al., 2003

NanoencapsulationSpecific methods:Phase inversion quercetin and EGCG Barras et al., 2009Nanoprecipitation curcumin Anand et al., 2010Nanoprecipitation quercetin Wu et al., 2008Emulsionediffusioneevaporation ellagic acid Bala et al., 2006Amphiphilic copolymers resveratrol Shao et al., 2009Ionotropic gelation tea catechins Hu et al., 2008Adsorption to prepared nanoparticles(layer-by-layer assembly)

EGCG, tannic acid, curcumin,and theaflavin

Shutava et al., 2009b

Yeast cellschlorogenic acid Shi et al., 2007

EmulsionsSystems:Tween 20-BSA- Fe (III)- sunflower oil O/W emulsion caffeic acid Almajano et al., 2007Tween 20-BSA- sunflower oil O/W emulsion Tea extract Almajano et al., 2008Tween 20-phosphate buffer-olive oil O/W emulsion Gallic acid, catechin, quercetin Di Mattia et al., 2009



stabilise the colloidal properties towards physical instabil-ity, while showing low activity towards secondary oxida-tion. Catechin showed an interfacial localisation whichwas reflected in the enhancement of primary oxidationand in the inhibition of secondary oxidation. Quercetinwas poorly partitioned in the aqueous phase and had no ef-fect on slowing down the bimolecular phase of auto-oxida-tion (Di Mattia, Sacchetti, Mastrocola, & Pittia, 2009).These results suggested that not only polarity but also anti-oxidant activity, can affect the polyphenol protective roletowards lipids auto-oxidation in emulsions.

Summary and trendsThe abundant work on encapsulation of polyphenols is

summarized in this paper. The characteristics of capsulesproduced by the various encapsulation processes are illus-trated in Fig. 2, which also shows that the different morphol-ogies can be achieved by these techniques. All of the workreported and summarized in this paper, has been undertakensince the year 2000 (Table 2), with the research and relatedreporting indicating the current worldwide interest in thesubject. From the literature, it is clear that the utilizationof encapsulated polyphenols instead of free compounds,can lead to improvements in both the stability and bioavail-ability of the compounds in vivo and in vitro, and optimizeroutes for their administration. Although most of the encap-sulation technologies employed for other chemicals havebeen adopted in polyphenol encapsulation, there are stillsome technologies not being applied for these special phyto-chemicals, including spray cooling/chilling, spinning diskand centrifugal coextrusion, extrusion and fluidized bed.However, this does not necessary mean that these technolo-gies are not suitable for polyphenol encapsulation.

Because there is still a lack of direct evidence for the useof polyphenols in preventing and treating of human dis-eases (Scalbert, Manach et al., 2005), most of the polyphe-nol encapsulated particles are classified as ‘functionalfoods’ or ‘nutriceuticals’, which limits their potential mar-kets. In food grade products, cost is an important factor fortheir industrialization. Yeast encapsulation of chlorogenicacid is an example of a successful low cost but high volumeprocessing (Shi et al., 2007). Future research of polyphenolencapsulation is likely to focus on aspects of delivery andthe potential use of co-encapsulation methodologies, wheretwo or more bioactive ingredients can be combined to havea synergistic effect. It can be foreseen that, with a deep un-derstanding of the health benefits of polyphenols, improve-ments in manufacturing technologies, new strategies forstabilization of fragile nutraceuticals, and the developmentof novel approaches to site-specific carrier targeting, encap-sulated polyphenols will play an important role in increas-ing the efficacy of functional foods or evenpharmaceuticals, over the next decade.

AcknowledgementThis work is supported by the Postdoctoral Research

Fellowship of The University of Queensland. The authorsthank Dr John Schiller for his professional proof reading.

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