Journal of Food Engineering 108 (2012) 158–165

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Journal of Food Engineering

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Influence of different pectins on powder characteristics of microencapsulatedanthocyanins and their impact on drug retention of shellac coated granulate

Sonja Berg ⇑, Manuela Bretz, Eva Maria Hubbermann, Karin SchwarzInstitute of Human Nutrition and Food Science, University of Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany

a r t i c l e i n f o

Article history:Received 9 May 2011Received in revised form 28 June 2011Accepted 29 June 2011Available online 14 July 2011

Keywords:AnthocyaninsPectinMicroencapsulationControlled releaseIn vitroWaterbinding

0260-8774/$ - see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.jfoodeng.2011.06.035

⇑ Corresponding author. Tel.: +49 431 880 5034; faE-mail address: info@foodtech.uni-kiel.de (S. Berg

a b s t r a c t

Blueberry extract was spray dried using different pectins and caffeine as copigment for anthocyanins inorder to influence the release of anthocyanins from the shellac coated maltodextrin granulates in simu-lated gastric fluid. The addition of pectin did not have any influence on the structure of spray dried micro-capsules as well as on the coating layer of the granulates. The initial retention of anthocyanins dependedsignificantly on the waterbinding ability of spray dried microcapsules. The higher the waterbindingcapacity of spray dried powders the lower was the anthocyanin release. Highest waterbinding capacityand lowest anthocyanin release was gained by citrus pectin with a high degree of esterification (DE)and sugar beet pectin. In general high DE pectins inhibited the release stronger than low DE pectins.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Anthocyanins are well known as colourants and as bioactivecompounds derived from various plants and fruits. They are con-sidered to display antioxidative antiinflammatory and antimicro-bial activities, to reduce the blood pressure, to improve eyesight,and suppress the proliferation of human cancer cells (Dimantovet al., 2004). With respect to the reduction of colon cancer riskthe anticancerogenic effect is rather related to the local concentra-tion in the colon but to the plasma concentration. Anthocyaninsare considered to be directly absorbed by colon epithelia cells(Wang and Stoner, 2008; Wu et al., 2006). The delivery of intactanthocyanins to the colon is difficult to achieve due to the instabil-ity of anthocyanins at alkaline pH values, oxygen and light(Thomasset et al., 2009) and their fast resorption in the stomachand the small intestine (Talavéra et al., 2005; He et al., 2009).

Microencapsulation of sensitive food ingredients such as antho-cyanins may be a useful method to protect bioactives until theyreach the target organ. It is well established that microencapsulationby spray drying protects bioactives against disadvantageous envi-ronmental influences such as temperature, light and oxygen as wellas against pH values in the human gastro intestinal tract (GIT) (Ré,1998; Arshady, 1993; Gibbs et al., 1999; Ahrné et al., 2008). Malto-dextrin is often used as wall material for microencapsulation. Toencapsulate anthocyanins and betacyanins maltodextrin with

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x: +49 431 880 5544.).

dextrose equivalents between 10 and 25 were used (Cai and Corke,2000; Ersus and Yurdagel, 2007). However beside its food grade sta-tus and low costs the high water solubility of maltodextrin (Chiouand Langrish, 2007) counteracts a retarded release in the GIT.

The reduction of water solubility can be achieved by a waterinsoluble coating of the capsule. Coatings are established for phar-maceuticals providing controlled release of drugs. In the foodindustry coatings for a controlled release have raised interest re-cently (Desai and Park, 2005). Most pharmaceutical coating sub-stances are not permitted for food use except shellac. It is ofspecial interest for the application in health supplements andnutraceuticals (Krause and Müller, 2001). The use of shellac ascoating material may be limited due to its low mechanical stabilityand permeability in digestion media (Luangtana-anan et al., 2010).To compensate the lack of impermeability of shellac coating films amodification of the coated core might be a useful method. The useof gelling substances like pectin may prolong the solubilisationtime of the core materials. Pectin is a plant polysaccharide whichis not degraded by GIT enzymes; therefore it is used in pharmaceu-tical applications for colon targeting (Chourasia and Jain, 2003).Pectins are well known for their use as drug carrier for deliveryto the gastrointestinal tract. They are used in matrix tablets as wellas film coated dosage forms (Sriamornsak, 2003). The gellingmechanism of different pectin types depends on their DE. Lowesterified pectins gel in the presence of sugar and acid conditions(Willats et al., 2006) whereas high esterified pectins require thepresence of cations like calcium. Amidated pectins need lesscalcium than non amidated pectins (Sato et al., 2008; Sriamornsak,

Table 2Composition (total solids, %) of the feed solution.

Total solids (%)

Control +Pectin +Caffeine

Maltodextrin 67 65 64.33Blueberry-Extract 20 20 20Pectin 0 2 2Citric Acid 13 13 13Caffeine 0 0 0.67

S. Berg et al. / Journal of Food Engineering 108 (2012) 158–165 159

2003; Willats et al., 2006). For instance, high methylated pectinsare used as compression coats in pharmaceutical products(Chourasia and Jain, 2003). Pectins are also known as copigmentsfor anthocyanins (Maier et al., 2009). The stabilization mechanismdepends on molecular interactions of anthocyanins. In the foodindustry pectins are mainly used as thickening and gelling agents(Sriamornsak, 2003).

Kopjar et al. (2007) reported a stabilizing effect depending onthe degree of esterification in strawberry jam. Further stabilizationof anthocyanins can occur due to copigmentation reactions withcaffeine (Asen et al., 1972). Due to the intermolecular copigmenta-tion reaction the molecule is enlarged and the diffusive releasemight be reduced.

The aim of the present study was to investigate anthocyaninretention of spray dried shellac coated granulates in in vitro disso-lution experiments. The focus of this study was on the compositionof the matrix capsule investigating the effect of different pectintypes. Further, the effect of enlarging the antocyanin moleculewas studied using caffeine as copigment.

2. Material and methods

2.1. Materials

Blueberry extract rich in anthocyanins was donated byKaden Biochemicals GmbH (Hamburg, Germany). The extract con-tained approximately 25% anthocyanidins as well as other polyphe-nols, tannins, carbohydrates and fibres. Different pectins, namelycitrus and apple pectin with varying DE, sugar beet pectin and ami-dated pectin (Table 1) were donated by Herbstreith & Fox KG(Neuenbürg, Germany). Maltodextrin (C⁄Dry 01915, DE 18.5,Cargill Deutschland GmbH, Krefeld, Germany) was used as wallmaterial for microencapsulation. SSB Aquagold� donated by Stro-ever GmbH & Co. KG (Bremen, Germany) was used as coatingmaterial to achieve an enteric resistant coating of microcapsules.Flake–shellac (SSB57 Pharma, Stroever GmbH & Co. KG, Bremen,Germany) was used as binder solution. Citric acid and caffeine werepurchased from Carl Roth GmbH & Co. KG (Karlsruhe, Germany). Allother chemicals were of analytical grade.

2.2. Microencapsulation

For microencapsulation a suspension with 30% total solids wasprepared. Blueberry extract content was set at 20% (w/w) of totalsolids (Table 2). The feed solution was prepared with maltodextrinas the main wall forming compound, citric acid, pectin and caffeine.Concentration of galacturonic acid was in a similar range (83–87%)for citrus and apple pectins whereas sugar beet pectin had a lowergalacturonic acid concentration of 65% and amidated pectin a high-er galacturonic acid concentration of 92% (Table 1). All wall formingingredients were solved in tap water (containing 92.4 mg Ca2+ and10.2 mg Mg2+ per L; tap water analysis of waterworks Kiel Schulen-see, Germany). Thereafter blueberry extract was added and the feedsolution was mixed for 2 min with a hand blender. Afterwards pH

Table 1Characterisation of used pectins.

Type of pectin Degree ofesterification (%)

Concentration ofgalacturonic acid (%)

Apple low DE 39 86Apple high DE 70 83Citrus low DE 38 87Citrus high DE 71 84Sugar beet 55 65Amidated2 29 92

2 Degree of amidation 21%.

was adjusted to pH 2 to stabilize anthocyanins in the feed solution.Prior to the spray drying process the viscosity of the feed solutionswas determined using a rotational viscometer (100 rpm; spindleL1/L2) at room temperature (Haake Viscotester VT 7L, ThermoElectron Corporation, Dreieich, Germany) to establish the influenceof the viscosity on the particle morphology and particle size. Spraydrying was performed at 160/70 �C on a laboratory scale spraydryer (1–7 kg/h water evaporative capacity, Mobile Minor, Niro A/S, Denmark) with a rotating disk (SL 24-50/M) for atomisation. Diskrotation was set at approximately 23,000 rpm (4 bar). A magneticstirrer was used to prevent sedimentation of insoluble compoundsin the feed solution during spray drying.

2.3. Coating

Prior to the coating process the matrix capsules were granu-lated with ethanolic shellac solution (10% (w/v)) as binder in agranulating pan (self-construction). Coating solution consisted of36.9% aqueous shellac solution, 24.4% deionised water, 1.8% glycer-ine and 36.9% hydroxypropyl methylcellulose (HPMC) solution(10% (w/v)). Coating process was performed in a laboratory scalefluidized-bed coater with Wurster insert (Mini Glatt, Glatt GmbH,Binzen, Germany). The size of the used granulates ranged between250 and 500 lm prior to the coating process. Operating conditionswere as follows: inlet air temperature: 80 �C; product tempera-ture: 50 �C; process air pressure: 0.35 bar; spray rate: 1 g/min;atomizing air pressure: 1.45 bar; spray nozzle diameter: 0.5 mm.25 g polymer was used per 100 g granulated microcapsules. Final-ly, the coated microcapsules were dried for 30 min at 40 �C in adrying oven and were classified in a range between 250 and500 lm.

2.4. Physicochemical characterisation

The morphology of spray dried microcapsules and coated gran-ulates was analysed by a SEM CamScan 44 REM/EDX scanning elec-tron microscope (CamScan USA Inc., Cranberry Township PA, USA).Magnification ranged between 400 and 900� for spray dried cap-sules and 70� for coated granulates. Particle size of microcapsuleswas determined by laser-diffraction (Helos, Sympatec GmbH,Clausthal-Zellerfeld, Germany, equipped with a cuvette). An ali-quot of microcapsules was dispersed in medium-chain triglycer-ides (MCT oil). True density of the spray dried microcapsules andthe coated granules were determined using a Pycnomatic ATC he-lium pycnometer (POROTEC GmbH, Hofheim/Ts., Germany).Waterbinding capacity of spray dried particles was performedaccording to Anderson et al. (1970) with slight modifications. 1 gglass beads were put into a screw cap centrifuge vial. 1 g (Wi) spraydried particles were added (Wt) and covered with 10 ml simulatedgastric fluid (SGF, pH 1.2, enzyme free). The samples were centri-fuged for 60 min at 500g to penetrate the powder with SGF. There-after samples were stored at 40 �C for 1 h. To generate solidsediment the samples were centrifuged for 30 min at 1500g. Thesupernatant was decanted into tared aluminium pans to calculatethe amount of solved substances. The aqueous phase was

160 S. Berg et al. / Journal of Food Engineering 108 (2012) 158–165

evaporated and the residue corresponds to (Ws). The sediment inthe centrifuge vial corresponds to (Wf). The waterbinding capacitywas calculated by the following equation:

Waterbinding capacityð%Þ ¼ ðWf þWsÞ �Wt

Wi� 100 ð1Þ

All analyses were performed with three replicates.

2.5. In vitro dissolution

Anthocyanin release of coated microcapsules was evaluated byusing the paddle apparatus (USP dissolution apparatus 2) (DT 70,Pharmatest AG, Hainburg, Germany). Rotation speed was set at100 rpm at 37 �C. Enzyme-free simulated gastric fluid (SGF) (USP,2008) (2 g NaCl and 7 ml HCl were added to 1 L deionised water,pH was adjusted to 1.2) was used as dissolution medium. 1 gcoated microcapsules was added to 500 ml of preheated dissolu-tion medium. Anthocyanin release was measured every 10 minfor 120 min (European Pharmacopeia 5.7 for delayed-release dos-age forms method B). All dissolution runs were performed intriplicate.

Anthocyanin release data were corrected for losses of dissolu-tion medium volume during sampling using the following Eq. (2)according to Singh et al. (1997).

Cin ¼ An þVs

Vt

� � Xi¼1

n

Ai � n� An

!ð2Þ

where Cin is the corrected absorbance of the nth observation, An isthe observed specific absorbance of the nth observation, Ai is theuncorrected absorbance of measurement 1 to n, Vs is the samplevolume, Vt is the total volume of dissolution medium.

Anthocyanin retention corresponds to the initial anthocyaninconcentration mg/l (100%) subtracted by the anthocyanin releasein mg/l.

2.6. Anthocyanin content

Total anthocyanin content was measured according to Giustiand Wrolstad (2001). The absorbance of each sample was mea-sured using a UV–Vis photometer (Hekios�, Thermo Electron Cor-poration, Thermo Fisher Scientific Inc. Waltham, USA) at 510 nm(A510) and 700 nm (A700) at pH 1 and 4.5 against distilled water.Samples were diluted, 3 ml sample was diluted with buffer solu-tion made up to a final volume of 10 ml. The absorbance (A) ofthe samples was calculated according to the following equation:

A ¼ ðA510 � A700Þ pH1 � ðA510 � A700Þ pH4:5 ð3Þ

The concentration (mg/l) anthocyanins was calculated accord-ing to the following equation and expressed as cyanidin-3-gluco-side equivalents:

Table 3Viscosity of the feed solutions and particle size of spray dried anthocyanins.

Viscosity (mPas) Particle size (l

10th percentile

Maltodextrin 9 7.28 ± 0.14Apple low DE 64 9.66 ± 0.18Apple high DE 59 5.49 ± 0.06Citrus low DE 96 9.33 ± 0.11Citrus high DE 57 5.16 ± 0.12Sugar beet 27 5.09 ± 0.22Amidated 17 5.98 ± 0.40Citrus low DE + caffeine 37 7.44 ± 0.19Citrus high DE + caffeine 55 5.45 ± 0.26Sugar beet + caffeine 32 5.08 ± 0.06Amidated + caffeine 16 7.34 ± 0.30

Monomeric anthocyanin pigmentðmg=LÞ¼ ðA�MW � DF � 1000Þ=ðe� 1Þ ð4Þ

where A is the absorbance in Eq. (3), MW is the molecularweight = 449.2 g/mol for cyanidin-3-glucoside, DF is the dilutionfactor and e is the extinction coefficient 26,900 for cyanidin-3-glu-coside, 1 = path length of the cuvette in cm.

2.7. Statistical analysis

The statistical calculation of dissolution profiles war carried outwith the Statistical Software Package SPSS 17 for Windows (SPSS,Chicago, IL, USA). One-way ANOVA was performed according toBonferroni (p < 0.05). Levene’s test was used to test for homogene-ity of variance. Two-tail Pearson’s correlation was performed aswell.

3. Results

3.1. Particle morphology and density

Feed solutions differed in the molecular weight and the DE va-lue of the used pectins as well as in the addition of caffeine as addi-tive. The lowest viscosity of 9 mPas was found in the referencesolution without added pectin. The particle size of the spray driedanthocyanins (50th percentile) conforming microcapsules was in anarrow range between 15 and 21 lm. The viscosity did not mark-edly affect the particle size (Table 3). Most particles shrunk duringthe spray drying process (Fig. 1). The intensity of shrinkage withinthe samples did not differ visibly.

The density of spray dried microcapsules was in a narrow rangebetween 1.32 and 1.45 g/cm3. The addition of high esterified pec-tins led to a higher particle density than the addition of low ester-ified pectins. The addition of caffeine lowered the particle densityslightly except for sugar beet containing sample where the densitywas not affected by the caffeine addition. In general the density ofthe coated granulates was lower than the density of the corre-sponding microcapsules (Table 4). The density decreased in aver-age by 0.1187 g/cm3.

3.2. In vitro dissolution

SEM pictures of the granulated and coated microspheres werecharacterised by a typical raspberry shape and exhibited a smoothcoating surface (Fig. 3). Also the thickness of the coating film issimilar in all samples (Fig. 2). However, samples containing applelow DE pectin, amidated pectin and amidated pectin + caffeinecontained small, probably uncoated particles (Fig. 2,3).

The maximum anthocyanin content of the samples varied be-tween 65.61 mg/l for the pectin-free sample and 78.94 mg/l for

m)

50th percentile 90th percentileP

17.32 ± 0.10 30.83 ± 0.88 55.4221.25 ± 0.10 38.19 ± 2.07 69.1015.96 ± 0.21 32.41 ± 0.75 53.8620.41 ± 0.21 35.12 ± 0.90 64.8616.06 ± 0.20 33.97 ± 0.18 55.1915.41 ± 0.60 32.72 ± 2.23 53.2117.43 ± 0.28 35.84 ± 2.50 59.2518.27 ± 0.63 34.85 ± 2.97 60.5616.49 ± 0.45 34.13 ± 0.95 56.0714.92 ± 0.15 29.43 ± 0.50 49.4318.44 ± 0.66 34.81 ± 1.01 60.59

Fig. 1. SEM-Pictures of spray dried microcapsules A = maltodextrin (control); B = Apple low DE; C = Sugar beet; D = Amidated; E = Citrus low DE; F = Citrus low DE + Caffeine.

S. Berg et al. / Journal of Food Engineering 108 (2012) 158–165 161

the sample containing sugar beet pectin + caffeine. These valuescorresponded to 100% in the dissolution experiments. Retentiondata were calculated for every time point (Table 5).

The course of anthocyanin retention (Fig. 4) was similar in allsamples. Within the first 10 min there was a strong release ofanthocyanins followed by a slow but continuous release. Theanthocyanin retention of Apple low DE, Amidated, Sugar beet + caf-feine and Amidated + caffeine corresponded to the pectin-free con-trol sample after the first 10 min of dissolution testing. Theremaining samples namely Apple high DE, Citrus low DE, CitrusHigh DE, Sugar beet, Citrus low DE + caffeine and Citrus HighDE + caffeine showed significant higher initial anthocyanin reten-tion. The addition of caffeine had no significant effect on of theretention profiles of shellac coated microcapsules. Except of Citruslow DE, the retention in caffeine-free samples was higher com-pared to the caffeine added samples. After 120 min of dissolution

Table 4True density of spray dried microcapsules and coated granulates.

Sample Spray dried microcapsules(g/cm3)

Coated granulate(g/cm3)

Maltodextrin 1.4333 ± 0.0095 1.2058 ± 0.0045Apple low DE 1.3896 ± 0.0056 1.2860 ± 0.0038Apple high DE 1.4569 ± 0.0052 1.3370 ± 0.0023Citrus low DE 1.4215 ± 0.0061 1.3058 ± 0.0040Citrus high DE 1.4326 ± 0.0062 1.2577 ± 0.0034Sugar beet 1.3944 ± 0.0072 1.2454 ± 0.0034Amidated 1.4152 ± 0.0097 1.2701 ± 0.0025Citrus low DE + caffeine 1.3804 ± 0.0037 1.3079 ± 0.0030Citrus high DE + caffeine 1.4050 ± 0.0036 1.3212 ± 0.0012Sugar beet + caffeine 1.3988 ± 0.0034 1.3234 ± 0.0017Amidated + caffeine 1.3247 ± 0.0051 1.2862 ± 0.0048

testing Citrus low DE, Citrus High DE, Sugar beet, Amidated andCitrus low DE + caffeine exhibited a significant higher anthocyaninretention than the maltodextrin sample (control). Low DE pectinsshowed a lower retention than high DE pectins. Apple low DE af-fected the retention even negatively compared to the control.

3.3. Waterbinding capacity

The waterbinding capacity of spray dried particles in the pectin-free control sample was lower than in the pectin containing sam-ples, excepted of amidated pectin (Fig. 5). The addition of caffeinelowered the waterbinding capacity slightly but not significantly.The waterbinding capacity correlates significantly with the initialretention of anthocyanins during dissolution testing.

After the dissolution procedure, light microscopic pictures weretaken to investigate the particle structure (Fig. 6). With few excep-tions, all particles exhibited an almost spherical shape, only someparticles were burst. Intact dyed particles were still available after120 min of dissolution testing, i.e. encapsulated anthocyanins werestill enclosed in the microparticle. Only for Apple low DE (B) theparticle structure was almost completely destroyed. Particles wereirregulary swollen and burst.

4. Discussion

Blueberry extract was spray dried using different pectins andcaffeine in order to influence the release of anthocyanins fromthe shellac coated granulates in SGF. All parameters for the spraydried powder were in a quite narrow range, i.e. neither the varia-tion of pectins nor the addition of caffeine resulted in a significantdifference of the particle size, density and shape. All spray dried

Fig. 3. SEM-Pictures of shellac-coated granulates to characterise the coating surface. A = maltodextrin (control); B = Apple low DE; C = Sugar beet; D = Amidated; E = Citruslow DE; F = Citrus low DE + Caffeine.

Fig. 2. LM-Pictures of shellac-coated granulates to characterise the thickness of the coating film. A = maltodextrin (control); B = Apple low DE; C = Apple high DE; D = Citruslow DE; E = Citrus high DE; F = Sugar beet; G = Amidated; H = Citrus low DE + Caffeine, I = Citrus high DE + Caffeine; J = Sugar beet + Caffeine; K = Amidated + caffeine.

162 S. Berg et al. / Journal of Food Engineering 108 (2012) 158–165

powder particles showed a wrinkled structure in SEM pictures.This morphology is due to the low temperature used for spray dry-ing as reported by Alamilla-Beltrán et al. (2005), Tonon et al.(2008). In this trial the true densities of the spray dried micro-capsules ranged between 1.32 and 1.45 g/cm3 which are indicativefor small vacuoles. Drusch and Schwarz (2006) reported true den-sity of 0.87 and 1.00 g/cm3 for high vacuolated microparticles

consisting of glucose syrup and n-OSA-starch and fish oil comparedto 1.09 and 1.34 g/cm3 for low vacuolated particles.

The strong initial increase for the anthocyanin release from theshellac coated granulates was a quite remarkable result as shellacis considered to result in a stomach resistant coating (Stummeret al., 2010). This effect was attributed to the fine particles thatare included in the coating surface of capsules (Fig. 2). The Wurster

Table 5Maximum anthocyanin content of coated granulates. Anthocyanin retention data (%) during 120 min of dissolution testing in SGF pH 1.2, enzyme-free. Values in the same columnmarked by different letters are significantly different (p < 0.05, Bonferroni).

Sample Anthocyanin content (mg/l) Dissolution time (min) (retention (%))

0 10 30 120

Maltodextrin 65.6 ± 1.0 100.0 ± 0.0 41.5 ± 2.4ab 32.5 ± 4.6bc 26.0 ± 1.4b

Apple low DE 76.5 ± 0.6 100.0 ± 0.0 33.6 ± 1.8a 19.1 ± 1.8a 6.4 ± 1.4a

Apple high DE 73.6 ± 2.2 100.0 ± 0.0 55.2 ± 4.0cde 38.0 ± 3.8bcde 25.5 ± 1.4b

Citrus low DE 70.6 ± 0.7 100.0 ± 0.0 58.2 ± 2.8def 46.8 ± 2.7efg 35.6 ± 0.1cd

Citrus high DE 71.4 ± 0.6 100.0 ± 0.0 67.8 ± 2.8fg 52.9 ± 3.1fg 36.9 ± 4.3cd

Sugar beet 71.8 ± 0.5 100.0 ± 0.0 69.6 ± 1.9g 57.9 ± 6.2g 55.7 ± 1.8e

Amidated 68.5 ± 0.5 100.0 ± 0.0 51.0 ± 1.5bcd 43.9 ± 0.6def 39.5 ± 0.8d

Citrus low DE + caffeine 76.1 ± 2.0 100.0 ± 0.0 64.4 ± 0.6efg 51.5 ± 1.3fg 36.5 ± 2.4cd

Citrus high DE + caffeine 68.3 ± 0.8 100.0 ± 0.0 61.5 ± 3.6defg 43.4 ± 1.2cdef 28.7 ± 7.8bc

Sugar beet + caffeine 78.9 ± 1.5 100.0 ± 0.0 46.5 ± 1.3bc 33.9 ± 0.6bcd 22.4 ± 1.0b

Amidated + caffeine 77.0 ± 2.5 100.0 ± 0.0 41.5 ± 6.1ab 31.3 ± 3.8b 9.4 ± 0.5a

A

B

Fig. 4. Anthocyanin retention profiles during 120 min of dissolution testing (SGF, pH 1.2, enzyme free). A = Comparison of low DE pectin addition [Maltodextrin (�); Applelow DE (j); Citrus low DE (�), Amidated (+)]; B = Comparison of high DE addition [Maltodextrin (�); Apple high DE (N), Citrus high DE (⁄), Sugar beet (d)].

S. Berg et al. / Journal of Food Engineering 108 (2012) 158–165 163

coating process is known for homogenous coating with a goodcoating quality, however the process is characterised by its highmechanical impact on the particles (Wurster, 1966, 1965). Due tothe high mechanical burden, some of the granulated particles burstduring the coating process and fine particle dust is incorporatedinto the coating layer or cover the coated particle surface by elec-trostatic charge (Fig. 2A, B, G, H, K). The solving process of small,surface-near anthocyanin inclusions in the dissolution experimentwith SGF was much faster than the solving process of the main par-ticle. It was shown in the light microscopy pictures after the disso-lution procedure that except for granulates containing apple lowDE pectin all particles were still intact and intensively dyed bythe anthocyanins. I.e. the release of anthocyanins due to diffusionprocesses was initiated by the influx of the SGF and subsequentdiffusion of anthocyanins. The dissolution of small particles in

the surface may have resulted in a damage of the coating and par-ticularly promoted the influx of water resulting in the high initialrelease of anthocyanin in granulates containing apple low DE pec-tin, amidated pectin and amidated pectin + caffeine.

During the granulation process raspberry shaped granulateswere formed by solid bridges. This raspberry shape still exists afterthe coating process and provided a larger surface for the dissolu-tion process. Also, the raspberry shape may promote air inclusionswithin the granulate structure which was indicated by the de-crease in density compared to the spray dried powder. Duringthe dissolution process escaping air could damage the coating layerand anthocyanins may leak from the core.

The initial retention of anthocyanins was significantly corre-lated to the waterbinding capacity of the spray dried samples.Binding larger amounts of water resulted in higher anthocyanin

010

203040

50

6070

80

90100

Maltod

extrin

Apple lo

w DE

Apple hi

gh D

E

Citrus l

ow D

E

Citrus h

igh D

E

Sugar

beet

Amidated

Citrus l

ow D

E + Caff

eine

Citrus h

igh D

E + Caff

eine

Sugar

beet

+ Caff

eine

Amidated +

Caff

eine

Wat

erbi

ndin

g ca

paci

ty

[%/g

pow

de

ad

a

dei fghi deh

bcde

ac

defdeg

ae

ab

Fig. 5. Waterbinding capacity of spray dried microcapsules. Values in the same column marked by different letters are significantly different (p < 0.01, Bonferroni).

Fig. 6. LM-Pictures of shellac-coated granulates after 120 min of dissolution in SGF pH1.2, enzyme-free A = maltodextrin (control); B = Apple low DE; C = Apple high DE;D = Citrus low DE; E = Citrus high DE; F = Sugar beet; G = Amidated; H = Citrus low DE + Caffeine, I = Citrus high DE + Caffeine; J = Sugar beet + Caffeine;K = Amidated + caffeine.

164 S. Berg et al. / Journal of Food Engineering 108 (2012) 158–165

retention. The water influx may even result in a gelling processwithin the coated granulate. The bound water impairs osmotic ex-change with the surrounding digestion medium consequently theinitial retention of anthocyanins as well as the total retentionwas increased. Citrus and apple pectins are widely equivalent interms of their overall chemical composition (Sriamornsak, 2003).The used pectins have a nearly equal galacturonic acid content (Ta-ble 1). Nevertheless fine structures of pectins can be extremelyheterogeneous between plants (Willats et al., 2006). In this trialthe lowest water binding capacity was found for samples contain-ing amidated pectin. Highest viscosities were measured for highesterified citrus and apple pectin as well as for the low esterifiedcitrus pectin.

In this trial no calcium was added, however the samples wereprepared with tap water containing 92.4 mg Ca2+ and 10.2 mgMg2+ per l (tap water analysis of Waterworks Kiel Schulensee, Ger-many). This means that approx. 11 mg Ca2+ and 1.2 mg Mg2+ per gpectin were present in all samples. The introduction of amidegroups in low DE pectin reduces the hydrophilic property withan increasing tendency to form gels (Munjeri et al., 1997; Sinhaand Kumria, 2001; Vandamme et al., 2002; Liu et al., 2003).

Samples containing amidated pectin demonstrated a lowwaterbinding capacity and a low anthocyanin retention. This phe-nomenon might be attributed to the precipitation of pectinate dueto presence of Ca2+ in the tap water. However, low DE, high DA pec-tins were reported as colon-specific drug delivery systems(Munjeri et al., 1997; Sinha and Kumria, 2001; Vandamme et al.,2002; Liu et al., 2003).

Sugar beet pectin has a high content of acetyl groups which areresponsible for its poor gelling properties (Michel et al., 1985). Inthis trial sugar beet pectin showed a slight increase in the viscosity.This might be affected by phenolic compounds of the used blue-berry extract. It is known that sugar beet pectin is able to form gelsvia oxidative cross linking with ferulic acid. This gelation takesplace within a few minutes at room temperature (Norsker et al.,2000; Oosterveld et al., 1997; Liu et al., 2003). Such gels are knownfor a remarkable water absorbing capacity (Liu et al., 2003). Due toits emulsifying properties beet pectin is also known as wall mate-rial for the microencapsulation of sensitive food ingredients like offish oil (Drusch, 2007).

The addition of caffeine did not increase the retention ofanthocyanins in the coated granulate. The reported effect of

S. Berg et al. / Journal of Food Engineering 108 (2012) 158–165 165

copigmentation for anthocyanins and caffeine (Asen et al., 1972)did not affect the diffusion process from the coated granulates intothe SGF.

5. Conclusions

Lowering the initial diffusive release of encapsulated anthocya-nins from shellac coated granulates is the principal point of thisstudy. The use of gelling substances enabled an increase of antho-cyanin retention. The waterbinding capacity in combination withthe viscosity due to the use of pectins reduced the anthocyanin re-lease into the SGF. It can be concluded that pectins with a highwaterbinding capacity combined with a high viscosity increasedthe anthocyanin retention during the complete dissolution process.

Acknowledgement

This research Project was supported by the FEI (Forschungskreisder Ernährungsindustrie e.V., Bonn), the AiF and the Ministry ofEconomics and Technology, AiF Project No. 15613N. Scanningelectron microscopy was performed at the Institut für Geowissens-chaften, Abt. Geologie, University of Kiel. The authors gratefullyacknowledge the skilful help of Ute Schuldt, Arno Lettmannand Sandra Meier and thank the following companies for prov-iding sample materials: Kaden Biochemicals GmbH (Hamburg,Germany), Herbstreith & Fox KG (Neuenbürg, Germany), Stro-ever GmbH & Co. KG (Bremen, Germany).

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