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Physicochemical Characterization of Whole Egg PowderMicroencapsulated by Spray DryingMehmet Koçç a , Banu Koçç a , Melike Sakin Yilmazer a , Figen Kaymak Ertekin a , GoncaSusyal b & Neriman Bağğdatlııoğğlu b

a Department of Food Engineering, Faculty of Engineering, Ege University, Bornova, Izmir,Turkeyb Food Engineering Department, Faculty of Engineering, Celal Bayar University, Manisa,Turkey

Available online: 04 May 2011

To cite this article: Mehmet Koçç, Banu Koçç, Melike Sakin Yilmazer, Figen Kaymak Ertekin, Gonca Susyal & NerimanBağğdatlııoğğlu (2011): Physicochemical Characterization of Whole Egg Powder Microencapsulated by Spray Drying, DryingTechnology, 29:7, 780-788

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Physicochemical Characterization of Whole Egg PowderMicroencapsulated by Spray Drying

Mehmet Koc,1 Banu Koc,1 Melike Sakin Yilmazer,1 Figen Kaymak Ertekin,1

Gonca Susyal,2 and Neriman Bagdatlıoglu21Department of Food Engineering, Faculty of Engineering, Ege University, Bornova, Izmir, Turkey2Food Engineering Department, Faculty of Engineering, Celal Bayar University, Manisa, Turkey

Physical characterization and oxidative stability of egg powdermicroencapsulated by spray drying were studied in this work. Thewall material (gelatin, lactose, pullulan, and their mixtures) andliquid egg mixtures were prepared by homogenization at 22,000 rpmfor 60 s. The spray drying was carried out at pilot-scale spray dryer(Niro Mobile Minor, Søborg, Denmark). The spray-dried egg pow-ders were analyzed for moisture content, water activity, peroxidevalue, total cholesterol oxidation products (TCOPs), particleproperties, and bulk properties. Using gelatin as wall materialresulted in a significant increase in the moisture content and wateractivity of egg powder during storage and it improved flowability.Egg powders containing pullulan as wall material showed a fibrousstructure and had the lowest bulk density. Adding lactose as wallmaterial increased the oxidative stability, which was indicated withlowest peroxide value and TCOPs level of egg powder.

Keywords Egg powder; Microencapsulation; Oxidation; Particlecharacterization; Spray drying

INTRODUCTION

In modernization of the food industry, large eggconsumers faced with the need to further improve productquality and expand product varieties have had to reducemanufacturing costs. Recently, there has been an increasein demand for dried whole egg products in the food indus-try rather than traditional liquid eggs for handling andhygienic reasons. However, the drying process itself leadsto many changes in egg components, especially egg pro-teins, resulting in different functional properties of thewhole egg, such as emulsion stability, firm gel structure,and foaming stability after reconstitution. In addition,spray drying can induce oxidation of the fat fraction ofthe whole egg due to the high temperature effect and ahigher surface area of particles, leading to formation ofoxidation products.[1] Cholesterol oxidation products havea negative effect on health due to their carcinogenic andatherosclerosis effects.[2,3] Protection of lipid oxidation is

a critical factor for food quality and the shelf life of eggpowder in addition to functional properties.[4] The chemi-cal changes during storage have been studied by manyresearches investigating the effect of storage conditions,light, heat, packaging material, and time.[5,6] Micro-encapsulation of egg fat can be adopted as an approachto prevent oxidation of the egg.

The food industry applies microencapsulation for anumber of reasons such as stabilization of active sub-stances, controlled release of active substances, maskingunpleasant tastes and smells, and protecting ingredientsfrom oxidation.[7] The wall matrix, including carbohy-drates, proteins, gums, lipids, waxes, etc., is generally madeof compounds with chains to create a network, with hydro-philic and=or hydrophobic properties. The final powderhas a specific composition regarding the active component,but it must also have good handling properties and mixingability with water or other powders (size, shape, density).Air temperature, flow rate, and initial droplet diameter ina spray are the most important factors that affect thephysical properties of dry powders.[8] Flow properties ofa powder may also depend on the properties of the wallmaterial and, for example, on the relative amount of lipidsremaining uncapsulated on the surface of particles.[9]

Among several encapsulation techniques, spray drying isthe most widely used and low-cost method to produce afood powder.[10] However, the spray-dried powders usuallyhave a small particle size, 10–100 mm, with poor handlingand reconstitution properties. Some encapsulating agentshave been reported to improve the flowability and bulkproperties of the powders.[11]

For microencapsulation by spray drying, gelatin is agood choice as wall material due to its good properties ofemulsification, film formation, and water solubility; lowcost; and nontoxic nature.[12] Addition a small amount ofgelatin to sugar solutions causes formation of a thin gelatinfilm near the surface, as reported by Yamamoto et al.,[13]

and it reduces the drying rate. The film formation propertyof gelatin at the surface is advantageous; for example, if

Correspondence: Melike Sakin Yilmazer, Department of FoodEngineering, Faculty of Engineering, Ege University, 35100,Bornova, Izmir, Turkey; E-mail: melike.sakin@ege.edu.tr

Drying Technology, 29: 780–788, 2011

Copyright # 2011 Taylor & Francis Group, LLC

ISSN: 0737-3937 print=1532-2300 online

DOI: 10.1080/07373937.2010.538820

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gelatin is incorporated into the egg, it has the effect ofpreventing oozing out of the oily components intrinsicallycontained in whole egg during spray drying.[14] Hydro-carbon compounds are also used as a significant compo-nent of wall materials[15] due to promotion of theformation of spherical and smooth-surfaced microcapsulesand enhanced adhesion force between the wall and corematerials.[12] It is reported that the lipids of unaltered eggare associated with lipoproteins, and they cannot be easilyextracted with nonpolar solvents. On the other hand, theextractable fat content of egg increases because of thealtered structure of lipoprotein due to the effect of drying.In this case, the oxidation stability decreases because of thereleased fat on the large surface of dried egg particles. Thiscan be prevented by the addition of carbohydrates.[14]

Disaccharides such as lactose can replace water moleculesand thus preserve membrane structures. They also formhydrogen bonds with proteins, preventing their denatura-tion.[15] Problems associated with the use of low-molecular-weight carbohydrates in microencapsulation are cakingand structural collapse as well as recrystallization of theamorphous carbohydrate matrix upon storage. Pullulanis used as wall material due to its good water solubilityand film-forming properties and its ability to form anamorphous state on dehydration. It has the ability to formstrong films that are impermeable to oxygen, thus prevent-ing fat oxidation.[16] A single encapsulating matrix does notpossess all required characteristics, and efforts to improveencapsulation properties have been done by blending twoor more wall materials; for example, carbohydrates withproteins and polysaccharides at different proportions.[17,18]

A literature survey showed that there is a substantialamount of work on spray drying of whole egg, egg white,or egg yolk. However, no existing research has beenconducted on preventing oxidation of egg powder bymicroencapsulation of egg fat. This study was undertakento investigate the oxidation level (peroxide value and totalcholesterol oxidation products [TCOPs] analysis) andphysical properties of spray-dried egg powders micro-encapsulated with gelatin, lactose, pullulan, and theirmixtures in order to increase oxidative stability duringstorage.

MATERIAL AND METHODS

Materials

Pasteurized liquid whole egg (24% dry matter) as the testmaterial was supplied from a local producer (Mix FoodCompany, Izmir, Turkey) and kept atþ 4�C until used.

Gelatin, bloom value 200 (Cagdas Chemical, Istanbul,Turkey), lactose (Merck, Darmstadt, Germany), and pull-ulan (Hayashibara International Inc., Leatherhead, UK)were used as wall materials.

Sample Preparation

Lactose, pullulan, and=or gelatin were dissolved in dis-tilled water at 40�C and mixed with pasteurized liquidwhole egg after cooling according to compositions listedin Table 1. The ratio of protein to carbohydrate in the solu-tions (gelatin–lactose or gelatin–pullulan) was fixed at 1:1(w=w). The mixture was homogenized by a laboratory-typehomogenizer (IKA T25 ULTRA-TURRAX, Usingen,Germany) at 22,000 rpm for 60 s to produce fine droplets.

Spray Drying

The prepared mixtures were spray dried in a NiroMobile Minor (Copenhagen, Denmark) spray dryer equip-ped with an atomizer at operating conditions, determinedpreviously,[19] as follows: inlet air temperature 171.8�C,outlet air temperature 72.5�C, atomization pressure 392 kPa,feed temperature below 10�C, and hot air flow rate1.54m3=min. Dried powder was packed in hermeticallysealed aluminum laminated polyethylene (ALPE) pouches.

Storage

The prepared egg powders (100 g) were packed in ALPEpouches (120mm� 150mm), which were closed by heatsealing to avoid any air space but without vacuum appli-cation. Samples in ALPE pouches were stored in a clima-tized chamber (Daihan WGC-P4, Seoul, Korea) at 20�Cand 50% RH for 180 days. Pouches were placed in a verticalpouch holder to ensure that they did not contact each otherand the pouches were exposed to the same environment.One ALPE pouch was taken from the climatized chamberat regular 15-day intervals during the first 90 days’ storage

TABLE 1Composition of dry matter of mixtures as (g=g total dry mass * 100)

Samples Pasteurized liquid egg (%) Gelatin (%) Lactose (%) Pullulan (%)

E (Egg powder without wall material) 100 — — —GL (Gelatinþ lactose) 90 5 5 —G (Gelatin) 90 10 — —L (Lactose) 90 — 10 —GP (Gelatinþ pullulan) 90 5 — 5P (Pullulan) 90 — — 10

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and at 30-day intervals during the last 90 days’ storage andanalyzed for quality parameters such as moisture content,water activity, peroxide value, and TCOPs. Storage stagewas replicated under the same conditions.

Analysis

Moisture Content

Moisture content of egg powders was measured with ahalogen moisture analyzer (Ohaus MB45, Nanikon,Switzerland), set at 70�C, until constant weight, and corre-lated previously by the vacuum oven method at the sametemperature.[20]

Water Activity

The water activity (aw) values of egg powders weremeasured with a water activity measurement device (TestoAG 400, Lenzkirch, Germany), with a� 0.001 sensitivity.

Oxidation Level

Peroxide Value. Folch et al.’s[21] method was used toextract lipids from egg powder for peroxide value deter-mination. The method used determines all substances, interms of milliequivalents peroxide per 1,000 g of sample,that oxidize KI under the conditions of the test.[20]

Total Cholesterol Oxidation Products. Lipid extractionwas applied according to the method of Folch et al.[21] andthen COPs were purified from the unsaponifiable matteraccording to Rose-Sallin et al.[22] The eluted fraction wassilylated and then analyzed by gas chromatography (GC).[23]

An Agilent 5890 model GC (Santa Clara, CA) equippedwith a flame ionization detector and DB-1 capillary column(30m� 0.32mm i.d.) was used with hydrogen as the carriergas. The chromatographic conditions were as follows: oventemperature programmed from 250 to 325�C (3�C=min);injector and detector temperatures 325�C; split ratio 1:20;sample volume injected 2 mL; and gas flow rate 2mL=min. COP standards (cholest-5-en-3b,7b-diol; 5b,6b-epoxycholestan-3b-ol; 5a, 6a-epoxy-cholestan-3b-ol; cholestan-3b,5a,6b-triol; cholest-5-en-3-b-ol-7-one; cholest-5-en-3b,25-diol) were supplied by Sigma Chemical Co. (St. Louis,MO).

Particle Properties

Particle Morphology. The morphological properties ofegg powders (appearance and particle shape) were investi-gated by taking images via a scanning electron microscope(SEM, JSM-6060 JEOL, Tokyo, Japan).

Particle Size Distribution. The particle size distri-bution of the egg powders was measured using a laser lightdiffraction particle size analyzer (Mastersizer model S2000, Malvern Instruments Ltd., Worcestershire, UK) inwhich a small quantity of the powder was dispersed in

water and the particle distribution was monitored duringfive successive trials. The particle size was expressed asmean volumetric size D4.3 (De Brouckere mean diameter)and was calculated as follows:

D4;3 ¼P

nid4iP

nid3i

ð1Þ

where ni is the number of particles of diameter di. Theparticle size distribution of the powder was measured asthe span, which is defined as

span ¼ d90 � d10d50

ð2Þ

where d90, d10, and d50 are the equivalent volume diametersat 90, 10, and 50% cumulative volume, respectively.

Particle Density. Particle density (qp) of the powdersamples was analyzed according to a study by Barbosa-Canovas et al.[24] Liquid pycnometry can be used todetermine particle density depending on the volume ofthe pycnometer bottle used.

Bulk Properties

Bulk and Tapped Densities. The bulk density (qb) ofthe egg powders was determined by measuring the weightof the powder and the corresponding volume. Approxi-mately 20 g of powder sample was placed in a 100-mLgraduated cylinder. The bulk density was calculated bydividing the mass of the powder by the volume occupiedin the cylinder. For the tapped density (qt), the cylinderwas tapped steadily and continuously on the surface byhand until there was no further change in volume; 100tappings was determined to be enough in three parallelmeasurements.[25]

Porosity. Porosity (e) of the powder samples was calcu-lated using the relationship between the tapped (qt) andparticle (qp) densities of the powders as shown below[25]:

e ¼qp � qt� �

qt� 100 ð3Þ

Flowability. Flowability of the egg powders was eval-uated in terms of Carr index (CI).[26] CI was calculatedfrom the bulk (qb) and tapped (qt) densities of the powderas shown below:

CI ¼ qt � qbð Þqt

� 100 ð4Þ

Hygroscopicity. About 1 g of powder was spreadevenly on Petri dishes (4 cm diameter) to allow for a high

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surface area between humid air and powder. Powders inthe dishes were placed in desiccators containing saturatedNaCl solution providing 75.3% relative humidity at 25�C.A 10-min interval was selected to obtain the kinetics ofmoisture sorption. The gain in weight of the samples wasconsiderably lower after 90min. Although hygroscopicityis based on the equilibrium moisture content, to comparehygroscopicities, the weight increase per gram of powdersolids after being subjected to the atmosphere withrelative humidity of 75.3% for 90min was determined.[27]

Hygroscopicity was expressed as kg moisture=100 kg drysolids.

Degree of Caking. After determination of hygroscopi-city, the wet sample was dried in an oven at 102�C. Aftercooling, the dried sample was weighed and transferred intoa 500-mm sieve. The sieve was shaken for 5min in a shakingapparatus. The weight of the powder remaining in the sievewas measured. The degree of caking was calculated as[28]:

CD ¼ 100� b

að5Þ

where CD is the degree of caking (%), a is the amount ofthe powder used in sieving, and b is the amount of thepowder that remained on the sieve after sieving.

Statistical Analysis

All measurements were made in triplicate. Results areexpressed as mean plus or minus standard deviation.Analysis of variance (ANOVA) at a confidence level of95% was performed. All results were analyzed using SPSSsoftware (13.0 for Windows).

RESULTS AND DISCUSSION

Physical characterization of microencapsulated eggpowder has been reported and the change in its moisturecontent, water activity, and oxidation level during storagewas presented. Microencapsulation of the whole egg wasaimed to cover only the egg fat but not all of the constitu-ents of the whole egg. Although the egg constituents otherthan fat are in protein and carbohydrate structure, con-tributing to the capsulation of egg fat, capsulation materi-als such as gelatin, pullulan, and lactose were used in thisstudy to cover the egg fat further and prevent the fat fromoozing out from the powder particle to the surface.

Physical Characterization of the Microencapsulated EggPowder

Table 2 shows the physical characteristics of the differ-ent egg powders. Moisture content and water activity ofthe samples containing pullulan and pullulan þgelatin aswall material were higher than those containing lactose,gelatin, and gelatin þlactose, as well as egg powder withoutwall material. These results may be explained by the fibrousstructure and wide surface area of the samples containingpullulan.

However, moisture content and water activity of allsamples varied in the range of 1.83–3.35% (wet basis) and0.094–0.180, respectively, which is within the limits for safestorage. It is generally accepted that water activity shouldbe below 0.40[29] and thus moisture content below 5%(14) in order to ensure stability.

Particle and bulk properties of microencapsulated eggpowders, namely, particle, bulk, and tapped densities;porosity; degree of caking; flowability; and particle sizeare also shown in Table 2.

TABLE 2Physical characteristics of egg powders encapsulated with different coating materials

SamplesMC

(% wb) aw Morphological propertiesqb

(kg=m3)qt

(kg=m3)qp

(kg=m3)e

(%)CI(%) CD (%)

E 2.018(�0.08)

0.094(�0.005)

Smooth, slightly spherical,porous, small dents

305.06(�3.09)

493.27(�21.3)

871.15(�42.7)

43.34(�2.08)

38.09(�2.11)

55.88(�13.6)

GL 1.866(�0.11)

0.115(�0.005)

Smooth, closer to spherical,porous, small dents

317.49(�3.63)

463.08(�16.8)

851.06(�41.1)

45.46(�4.26)

31.38(�2.42)

47.84(�23.1)

G 1.830(�0.07)

0.094(�0.001)

Smooth, closer to spherical,porous, smallest dents

335.17(�1.41)

459.24(�13.9)

840.42(�36.5)

45.30(�2.55)

26.98(�1.91)

36.21(�17.4)

L 2.114(�0.09)

0.142(�0.009)

Smooth, amorphous,porous, high dents

339.72(�6.08)

542.92(�3.96)

861.23(�27.71)

36.50(�2.20)

37.42(�1.58)

54.16(�16.3)

GP 2.837(�0.24)

0.136(�0.001)

Fibrous, amorphous,agglomeration, porous,cracks

286.91(�3.34)

401.68(�4.68)

896.48(�32.28)

55.15(�1.79)

28.57(�1.43)

30.29(�15.2)

P 3.350(�0.18)

0.180(�0.002)

Very fibrous, amorphous,porous

247.75(�5.73)

341.75(�8.22)

807.04(�14.9)

57.49(�0.81)

27.45(�3.46)

32.06(�14.6)

GL¼ gelatinþ lactose; L¼ lactose; GP¼ gelatinþ pullulan; P¼ pullulan; G¼ gelatin; E¼ egg powder without wall material.

PHYSICOCHEMICAL CHARACTERIZATION OF WHOLE EGG POWDER 783

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The mean particle size of a material may greatly influ-ence its reactivity and the quality of the end product. Theparticle size distribution of spray-dried encapsulated eggswith different coating materials is shown in Fig. 1.

The results showed that spray drying does not producelarger particles. The particle size distribution showed thatall samples ranged from 0.32 to 120 mm, which is in accord-ance with the dimension limits (1–1,000 mm) of so-calledmicroencapsulated particles.[10] The mean diameter (D4,3)of microencapsulated egg powders was approximately4 mm, a relatively small diameter resulting from high atomi-zation pressure applied.[30] All microencapsulated powdershad a narrow particle size range with relatively uniformdistribution (Fig. 1). The samples’ span value, whichexpresses the width of the size distribution, varied from3.29 to 4.82.

The scanning electron microscope images of powdersmicroencapsulated with different wall materials are shownin Fig. 2; the properties of the images are also given in

FIG. 1. Particle size distribution of spray-dried egg powder encapsulated

with different coating materials. GL¼ gelatinþ lactose; L¼ lactose;

GP¼ gelatinþpullulan; P¼ pullulan; G¼ gelatin; E¼ egg powder with-

out wall material.

FIG. 2. Scanning electron microscope images of powders: (a) egg powder without wall material, (b) egg powder microencapsulated with gelatin and

lactose, (c) egg powder microencapsulated with gelatin, (d) egg powder microencapsulated with lactose, (e) egg powder microencapsulated with gelatin

and pullulan, and (f) egg powder microencapsulated with pullulan.

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Table 2. All powder particles other than pullulan wereobserved to have a shriveled appearance and show aporous structure caused by dents and the surface wassmooth. However, powder particles containing pullulanwere mostly observed to have a fibrous structure. Theporous surface is expected to be an advantage for improvedwetting and solubility.[31] The outer surface of powder con-taining lactose had the most dents among all particles. Ifthe skin remains moist and supple for a longer time, thehollow particles can deflate and shrivel as they cool, asstated by Birchal et al.[32]

The bulk properties of food powder are highly depen-dent on particle size and its distribution.[24] The bulk den-sities of samples were in the range of 248–340 kg=m3

(Table 2). The particle densities of powders varied from807 to 896 kg=m3 and no significant difference wasobserved (p> 0.05). Powders containing pullulan andgelatinþ pullulan had relatively low bulk density, whichwas associated with high porosity (eP: 57.49%, eGP: 55.15%;Table 2) and fibrous structure; the higher moisture contentof the powder resulted in a lower bulk density. On the otherhand, the bulk density of powders containing lactose washigher than other microencapsulated samples, because oflower particle diameter and more uniform distribution,although they had a higher moisture content. Also reportedby Shrestha et al.,[33] the increase in lactose concentrationcauses an increase in the density of powders.

Egg powders with lactose and without wall material hadpoor flowability (CIWE: 38.09%, CIL: 37.42%) values, dueto their small particle size. On the contrary, microencapsu-lation with gelatin and pullulan was found to improve flow-ability (CIG: 26.98%, CIP: 27.45%). Caking and stickinessare common problems in food powder handling and pro-cessing. The caking degree of the samples varied from30.29 to 55.88%. Adding gelatin and pullulan preventedcaking as it improved flowability. On the other hand, add-ing lactose resulted in a higher degree of caking because ofits small particle size. Kurozawa et al.[34] reported that asthe particle size of powder product decreases, the increase

in the particle surface area causes a higher affinity to moist-ure and caking during the drying process. The moistureadsorption of spray-dried egg powders at 25�C and75.3% relative humidity after 90min is shown in Fig. 3.Whereas adding lactose decreased the powder hygroscopi-city, adding gelatin and=or pullulan increased this value.

Moisture Content, Water Activity, and Oxidation Levelduring Storage

The variation in moisture content and water activity ofthe microencapsulated egg powders during storage isshown in Figs. 4 and 5. The ANOVA results (Table 3)showed that the moisture content of samples encapsulatedwith lactose and gelatinþ pullulan was not significantlyaffected by storage time (p> 0.05). Adding gelatin andpullulan resulted in a significant increase in the wateractivity of samples during storage (p< 0.05). At the endof the 6-month storage, the highest water activity valuewas found for the sample with pullulan, which was stillin the limits for safe storage.

FIG. 3. Hygroscopicity of egg powders at 25�C and 75.3% RH.

FIG. 4. Moisture content of the egg powders during storage. GL¼gelatinþ lactose; L¼ lactose; GP¼ gelatinþpullulan; P¼ pullulan;

G¼ gelatin; E¼ egg powder without wall material.

FIG. 5. Water activity of the egg powders during storage. GL¼gelatinþ lactose; L¼ lactose; GP¼ gelatinþpullulan; P¼ pullulan;

G¼ gelatin; E¼ egg powder without wall material.

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The oxidative stability of samples was evaluated by per-oxide value measurements and TCOPs analysis. Thechange in peroxide values and the amount of TCOPs(mg=g egg fat) versus storage time is shown in Fig. 6. Itcan be seen from Table 3 that the peroxide values andamount of TCOPs of all samples were significantly affectedby storage time (p< 0.05). The highest peroxide value(1.905meq O2=kg) was obtained for the egg powder with-out wall material, as well as the amount of TCOPs(128.7 mg=g egg fat). A high correlation (>0.97) wasobserved between peroxide value and the amount ofTCOPs by Pearson correlation (p< 0.05). The resultsshowed that using gelatin, lactose, and pullulan as wallmaterials caused a decrease in the oxidation level, probablydue to the ability of these wall materials to prevent the fatfrom oozing out. Powder containing lactose had the lowestperoxide value (1.772meq O2=kg) among the microencap-sulated egg powders after 6 months of storage. The amountof TCOPs was lowest (75.9 mg=g egg fat) for microencapsu-lation with lactose. It can be said that the powder samplescontaining lactose prevented oxidation, possibly due tolower porosity and higher bulk density, which minimizesthe trapped oxygen in pores. As reported earlier, the higherthe bulk density, the lower the occluded air within thepowders, which causes a reduced level of oxidation andincreases storage stability while lowering the package

TABLE 3ANOVA results for water activity, moisture content, and peroxide value and TCOPs level during storage

Water activity (aw) Moisture content (MC) Peroxide value TCOPs

Source dfMeansquare p-Value

Meansquare p-Value

Meansquare p-Value

Meansquare p-Value

E Between groups 9 0.001 0.002 0.046 0.115 0.235 0.000 4,625.501 0.000Within groups 10 0.000 0.021 0.000 39.388Total 19

GL Between groups 9 0.001 0.004 0.165 0.011 0.257 0.000 3,038.276 0.000Within groups 10 0.000 0.034 0.000 1.712Total 19

G Between groups 9 0.001 0.000 0.204 0.000 0.226 0.000 2,533.030 0.000Within groups 10 0.000 0.018 0.000 17.465Total 19

L Between groups 9 0.001 0.301 0.118 0.315 0.281 0.000 2,051.315 0.000Within groups 10 0.001 0.086 0.000 69.918Total 19

GP Between groups 9 0.000 0.289 0.099 0.041 0.279 0.000 3,289.184 0.000Within groups 10 0.000 0.031 0.000 8.924Total 19

P Between groups 9 0.001 0.001 0.086 0.007 0.258 0.000 3,346.073 0.000Within groups 10 0.000 0.015 0.000 3.930Total 19

GL¼ gelatinþ lactose; L¼ lactose; GP¼ gelatinþ pullulan; P¼ pullulan; G¼ gelatin; E¼ egg powder without wall material.

FIG. 6. Amount of TCOPs and peroxide values of the egg powders dur-

ing storage. GL¼ gelatinþ lactose; L¼ lactose; GP¼ gelatinþ pullulan;

P¼ pullulan; G¼ gelatin; E¼ egg powder without wall material.

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volume.[8,34,35] On the contrary, the powder samples con-taining pullulan had the lowest bulk density and highestporosity values, so the oxidation stability decreased withstorage (Fig. 6).

CONCLUSIONS

In this study, the physical properties and oxidative stab-ility of microencapsulated egg powders were investigated.The results of this study demonstrated that the moisturecontent and water activity of egg powders containing gela-tin were significantly (p< 0.05) affected by storage time andthe increase in moisture content due to the hydrophilicstructure of gelatin. Egg powders microencapsulated withonly pullulan showed a fibrous structure, impeding a shri-veled appearance. The other microencapsulated powderswere observed to have hollow dents and a smooth surface.According to the results of oxidation level analysis, themicroencapsulation process improved the oxidative stab-ility of egg powders. In addition, the results showed thatbulk properties of powders have a direct influence on oxi-dative stability. Higher bulk density and lower porosityvalues of powder can cause a decrease in oxidation levelbecause of less trapped oxygen in pores.

ACKNOWLEDGMENTS

The authors acknowledge TUBITAK-TOVAG (ProjectNumber: 108 O 541); Ege University, Council of ScientificResearch Projects (Project Number: BAP 2008=MUH=012); and Ege University, Science and Technology Center(Project Number: EBILTEM 09=BIL=014) for financialsupport. The authors also thank Mix Food Company,Izmir, Turkey, for material support.

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