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Food Hydrocolloids 25 (2011) 1596e1603

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Food Hydrocolloids

journal homepage: www.elsevier .com/locate/ foodhyd

Preparation of lutein microencapsulation by complex coacervationmethod and its physicochemical properties and stability

Xiao-Ying Qv, Zhi-Ping Zeng, Jian-Guo Jiang*

College of Food and Bioengineering, South China University of Technology, Guangzhou 510640, China

a r t i c l e i n f o

Article history:Received 21 September 2010Accepted 14 January 2011

Keywords:LuteinMicrocapsuleComplex coacervation methodStability

* Corresponding author. Tel.: þ86 20 87113849; faxE-mail address: jgjiang@scut.edu.cn (J.-G. Jiang).

0268-005X/$ e see front matter � 2011 Elsevier Ltd.doi:10.1016/j.foodhyd.2011.01.006

a b s t r a c t

Although lutein possesses multiple valuable physiological functions, its application in food industry islimited due to the instability in adverse conditions. Using the complex coacervation method, the work isaimed to optimize the encapsulation process, investigate physicochemical properties of microcapsulesand finally appraise the extent of stability improvement. The optimum process conditions determined byresponse surface analysis were as follows: concentration of wall materials 1.0%, ratio of core material towall 1.25:1 and pH value 4.2, where the theoretical and practical encapsulation efficiency were 86.41%and 85.32%� 0.63%. The particles had a confined distribution in the range of 0e30 mm, indicatinga relatively homogeneous distribution. Moreover, the lutein in particles presented an improvement ofability against light, humidity, temperature. Especially, the retention rate of lutein incorporated inproducts reached 92.86% at 4 �C, 90.16% at 25 �C, 90.16% with the relative humidity of 33%, and 90.25%under the aerobic condition.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Lutein is one type of carotenoid without bioactivity of vitamin Abut holding many other significant physiological functions. Asreported, the strong antioxidation inactivating singlet oxygenenables lutein to promote the enhancement of body immunityagainst arteriosclerosis, cataract (Calvo, 2005), and improve food andbeverage color due to its powerful coloration ability. However, itsapplication in food industry is limited by the instability towardsoxygen, light and temperature due to the eight conjugated doublebond structure. Taking lutein properties into account, the method-ologyofmicroencapsulation is adoptable for itsmultiple advantages.

Generally, microencapsulation referring to a methodology ofenveloping one or several materials intomicrocapsules (Champagne& Fustier, 2007; Li et al., 2009) has acquired broad applications infood industry for the protection of vitamins, minerals and othersensitive components from the external influences, improvement ofmaterial physical properties, isolatingproduct components,maskingunfavorable taste, and controlling the release of core materialsconsidered as the most important function (Champagne & Fustier,2007; Gouin, 2004; Im & Sah, 2009). The most commonly appliedtechnologies are emulsification, coacervation, spray drying (Teixeira,Andrade, Farina, & Rocha, 2004), spray cooling, freeze drying, fluid

: þ86 20 87113843.

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bed coating andextrusion technologies, etc. (deVos, Faas, Spasojevic,& Sikkema, 2010).

As a development of coacervation, complex coacervationmethod necessitates two or more linear and irregular polymerswith opposite charges served as wall materials. The common usedmaterial compositions include gelatin/gum arabic (GA), alginate/polylysine, gelatin/carboxymethylcellulose, albumin/gum arabic,etc. After the dissolution of wall materials and then the dispersionof core materials into water, coating materials electrostaticallycoagulate from the solution and encapsulate the core materials byadjusting pH and temperature or adding inorganic salt electrolyte(Huang, Cheng, Yu, Tsai, & Cham, 2007; Schmitt et al., 2001). Thepreparation is performed under gentle conditions applicable forlive cells and instable materials vulnerable to severe conditionchanges.

From an experimental and practical point of view, gelatin/gumarabic (GA) systemwas extensively utilized (de Kruif, Weinbreck, &de Vries, 2004; Malay, Bayraktar, & Batıgün, 2007). Gum arabic (oracacia gum) is a complex polysaccharide containing a proteinfraction responsible for its efficient surface property that is attrib-uted to the structure of the gum (Connolly, Fenyo, & Vandevelde,1987; Menzies, Osman, Malik, & Baldwin, 1996). Acacia gum is anarabinogalactan type polysaccharide composed of three distinctfractions with different protein contents and different molecularweights (Osman, Williams, Menzies, & Phillips, 1993; Phillips,Takigami, & Takigami, 1996; Randall, Phillips, & Williams, 1989).The highly efficient and practical approach can produce rigorously

X.-Y. Qv et al. / Food Hydrocolloids 25 (2011) 1596e1603 1597

wrappedmicrocapsules with coating thickness in awide adjustablerange, which is also nontoxic and degradable. For that reason,gelatin/gum arabic (GA) systemwas adopted in our experiment forexploring the optimization of process conditions by responsesurface analysis, assessing physicochemical properties and stabilityof products.

2. Materials and methods

2.1. Materials and apparatus

Gelatin (type B, 240 Bloom) was purchased from Tianjin Fu Yuchemical Co., Ltd and prepared for use with the isoelectric point at5.21. Gum arabic of food grades in spray dried from was alsopurchased from Tianjin Fu Yu chemical Co., Ltd. Lutein and itsstandard were both purchased from Shanxi Sciphar BiotechnologyCo., Ltd. WFJ2100 visible-infrared spectrometer was bought fromunique instrument Co., Ltd (Shanghai). S-3D pH meter was theproduct of Shanghai Precision and Scientific Instrument Co., Ltd.Diamond-I differential scanning calorimeter was purchased fromUSA Perkin Elmer company. OLYMPUS Scanning electron micro-scope, Mastersizer 2000 laser granulometer and BX51 polarizingmicroscope were from Hitachi Ltd. (Japan), Malvern InstrumentsLtd. (England), OLYMPUS Ltd. (Japan), respectively.

2.2. Optimization of lutein microencapsulation process

2.2.1. Designs of single factor experimentsSingle factor experiments were performed to determine

optimal conditions for single factors by analyzing their influencesto microencapsulation effect, which were concentration of wallmaterials (CWM) (gelatin/gum arabic, ratio 1:1), ratio of corematerial to wall (RCW), temperature and pH value. For studyingCWM effects on encapsulation, wall materials were prepared into0.5% (w/w), 1.0% (w/w), 1.5% (w/w), 2.0% (w/w), 2.5% (w/w) solu-tions, respectively. Then core materials were added according tothe 1:1 RCW and emulsified in water bath (45 �C, 30 min) at 550r/min stirring speed. Next, pH value of emulsion was adjusted to 4.4causing gelatin and gum arabic coagulate (at 550r/min stirringspeed, in 45 �C water bath for 15 min). After that, the pH value wasreadjusted to about 7.0 and then certain glycerin was added forimmobilization (at 350r/min stirring speed, in 0e10 �C water bathfor 30 min). Lastly, products were obtained after filtration anddrying. The other three single factor tests RCW, temperature, pHvalue took the similar process as the above. Their individualconditions were that (1) RCW: CWM 1% (w/w), ratios of corematerial to wall 3:1, 2:1, 1:1, 1:2, 1:3, temperature 45 �C, pH value4.4; (2) temperature: CWM 1% (w/w), RCW 1:1, temperatures30 �C, 35 �C, 40 �C, 45 �C, 50 �C, 55 �C, pH value 4.4; (3) pH value:CWM 1% (w/w), RCW 1:1, temperature 45 �C, pH values 3.5, 3.8,4.1, 4.4, 4.7.

2.2.2. Determination of lutein and encapsulation efficiencyThe lutein weighed precisely was dissolved and diluted with

anhydrous ethanol, and then formulated into 20, 40, 60, 80, 100,120 mg/ml standard solution, the absorption of which weresurveyed at 446 nm with ethanol as the blank, respectively. Thelinear regression of absorption (A) on concentration (C) was madeand the regression equation was calculated. The standard curvewas drawn and its equation is y¼ 0.011x� 0.0408, R2¼ 0.9998.A certain amount of sample weighed with precision was put intoa brown capacity bottle, added with anhydrous ethanol, treated inultrasonic water bath for 15 min, cooled into the room temperature,fixed to the calibration with anhydrous ethanol, mixed and filteredto measure its absorption and calculate its content.

Encapsulation efficiency is a significant indicator to appraise thequality of the prepared microcapsule products. The equitation is asfollows (Saravanan & Rao, 2010):

Eð%Þ ¼ w1

w2� 100%; (1)

where E is encapsulation efficiency,w1 andw2 represent theweightof lutein loaded in capsules and consumed for the encapsulationrespectively.

2.2.3. Response surface analysis of lutein microcapsule processOn the basis of the results of single factor experiments, the

experiments for optimization of microencapsulation process wasdesigned and carried out by response surface analysis takingencapsulation efficiency (Y) as response value and CWM (A), RCW(B), pH value (C) as factors.

2.3. Physicochemical properties of lutein microcapsules

2.3.1. Determination of water contentThe rate of water content in capsules was determined using the

vacuum oven to dry products, and figured out by the formula asfollows (Mendanha et al., 2009):

Cð%Þ ¼ w1 �w2

w2� 100%; (2)

where C is the water content rate, w1 is the weight of productsbefore dry treatment, and w2 is the weight after that operation.

2.3.2. Size distribution of microcapsulesA certain amount of microcapsule dispersion prepared under

the optimal process conditions and mixed homogenously, wastaken by pipette and diluted with water, and then assayed for sizedistribution by Mastersizer 2000 laser particle analyzer. Theaverage particle diameter formula is as follows:

Dn ¼Pn

i¼1 ni � diPni¼1 ni

; (3)

where Dn represents average diameter, ni refers to the number ofmicrocapsules and di is diameter of single microcapsule.

2.3.3. Scanning electron microscopyPrior to scanning electron microscopy (SEM) analysis, the

samples were sprinkled on one side of double-side adhesive stuckon the stub and thenwas coated with gold. The SEM analysis of themicrospheres was carried out by using S3700 scanning electronicmicroscope (Hitachi Japan). The microspheres were observed at anaccelerating voltage of 10 kV.

2.3.4. Determination of product liquidityThe repose angle method was taken to assess the liquidity of

microparticles. The product powder fell on the center of the discwith a certain diameter through the funnel placed on the iron standuntil the powder of the formed bulk automatically flew out alongthe disc edge. The included angle between the product-formedaccumulation and the plane is so-called the angle of repose.

2.3.5. Differential scanning calorimetryDifferential scanning calorimetry (DSC) was applied to detect

the glass transition temperature of products. The freeze driedsamples were added into the DSC sample box with the blank asreference (pans are sealed), and heated from 20 �C to 120 �C at therate of 5 �C/min.

Table 1Levels of three variables, BoxeBenhnken’s central composite design and responseresults for the study of microencapsulation.

Numbers Level Encapsulation rate

A B C

0.5% 2:1 4.11.0% 1:1 4.41.5% 1:2 4.7

1 0.5 1.25 4.7 0.7342 1 1.25 4.4 0.8173 1 0.5 4.7 0.834 0.5 1.25 4.1 0.7635 1 1.25 4.4 0.8046 1.5 0.5 4.4 0.7357 0.5 2 4.4 0.6928 0.5 0.5 4.4 0.7149 1.5 2 4.4 0.70410 1 0.5 4.1 0.78311 1.5 1.25 4.7 0.83312 1 1.25 4.4 0.80513 1 1.25 4.4 0.81114 1.5 1.25 4.1 0.77315 1 2 4.7 0.8416 1 2 4.1 0.79517 1 1.25 4.4 0.79

X.-Y. Qv et al. / Food Hydrocolloids 25 (2011) 1596e16031598

2.3.6. Infrared atlas analysis of microcapsules and wall materialsChlorine potassium was grinded with gelatin, gum arabic and

freeze dried products, respectively, to obtain three powders. Thenthe three prepared powders were made into transparent platesusing the presser. Finally, these plates were scanned by infraredinstruments at 500e4000 wavenumber.

2.4. Stability of lutein microcapsule

2.4.1. Determination of lutein retention rateThe lutein retention rate can be calculated by the following

formula:

Yð%Þ ¼ CACB

� 100%; (4)

where Y is lutein retention rate, CA and CB are lutein content existingin microcapsules after and before a time of storage, respectively.

2.4.2. Effects of relative humidity on lutein stabilityA certain amount of lutein and its microcapsule (freeze dried)

were separately kept in dark and 25 �C constant temperature incu-bator with different relative humidity of 33% and 80% respectively.Samples were taken every five days to examine lutein content for thecalculation of retention rate. The experiment period was thirty days.Relative humidity and its corresponding saturated solutionwere thatsaturated magnesium chloride solution (relative humidity 33%), andsaturated potassium iodide solution (relative humidity 80%).

2.4.3. Effects of light on lutein stability3.5 g of lutein and freeze dried microcapsules were preserved in

brown jars respectively at room temperature and avoiding light,while other equivalent samples were kept in transparent jars andlight. The preserved lutein and microcapsules were sampled 0.5 gto determine lutein content and figure out their retention rateevery five days in the consequent thirty days.

2.4.4. Effects of temperature on lutein stabilityFreeze dried microcapsules were weighed out 3.5 g, put in petri

dishes and kept at 4 �C, 25 �C, 50 �C without light, respectively, andsampled 0.5 g for examination of retention rate. The experimentlasted for thirty days.

2.5. Statistical analysis

The data were presented as mean� standard deviation (SD).Statistically significant differences between groups were evaluated

Table 2Analysis of variance of the regression parameters.

Source Sum of squares Df Mean squ

Model 0.032753 9 0.003639A 0.002521 1 0.002521B 0.00012 1 0.00012C 0.001891 1 0.001891AB 2.02E�05 1 2.02E�05AC 0.00198 1 0.00198BC 1E�06 1 1E�06A2 0.017899 1 0.017899B2 0.003529 1 0.003529C2 0.005321 1 0.005321Residual 0.002295 7 0.000328Lack of fit 0.00189 3 0.00063Pure error 0.000405 4 0.000101Total 0.035048 16R2

a Shows a highly prominence, P< 0.01.b Shows prominence, P< 0.05.

using Student’s test. Statistical significance was set at P< 0.05, Pvalues< 0.05 were regarded as significant and P values< 0.01 asextremely significant.

3. Results and discussion

3.1. Process optimization

The good levels of single factors concluded from single factorexperiments were as follows: CWM 0.5e1.5%, RCW 1:2e2:1 and pHvalue 4.1e4.7. On the basis of these results, taking encapsulationefficiency (Y) as response value of CWM (A), RCW (B) and pH value(C), experiments were arranged according to BoxeBenhnken’scentral composite design (Table 1). The levels of three variableswere listed in Table 1.

The experimental results shown in Table 1 were analyzed byDesign the expert 7.0, the regression equation is:

Yð%Þ ¼ 0:81þ 0:018A� 3:875Bþ 0:015C � 2:250AB

þ 0:022AC � 5:000BC � 0:065A2 � 0:029B2 þ 0:036C2:

are F-value Prob> F Significance

11.09786 0.0022 **a

7.686292 0.0276 *b

0.366323 0.56415.767006 0.0474 *0.061753 0.81096.038794 0.0436 *0.00305 0.9575

54.58355 0.0002 **10.76127 0.0135 *16.22728 0.0050 **

6.219974 0.0549

0.9345

X.-Y. Qv et al. / Food Hydrocolloids 25 (2011) 1596e1603 1599

The P value (lower than 0.01) signifies a highly remarkablelinear relationship between independent variable and dependentvariables. It can be concluded from Table 2 that the A, C, B2 andAC are prominent factors, and the influences of A2 and C2 are highlyprominent. The wall material to core ratio is a meaningful

Fig. 1. The contour plots of response surface methodology. (a) The response surface and contratio; (b) the response surface and contour plot of the effect of the wall material concentraticore/material material ratio and the pH value.

parameter in mixed biopolymer systems. It controls the balance ofmacromolecules charges and therefore, the intensity of the elec-trostatic interactions driving the formation of complexes betweenthe two biopolymers (Schmitt et al., 2000; Schmitt, Sancheza,Thomas, & Hardy, 1999).

our plot of the effect of the wall material concentration and wall core/material materialon and the pH value; (c) the response surface and contour plot of the effect of the wall

Fig. 2. (a) Particle size distribution of freeze dried microcapsules prepared under the optimal conditions; (b) particle size distribution of spray-dried microcapsules prepared underthe optimal conditions. A certain amount of microcapsule dispersion mixed homogenously was diluted with water, and then assayed with Mastersizer 2000 laser particle analyzer.

X.-Y. Qv et al. / Food Hydrocolloids 25 (2011) 1596e16031600

The response surfaces and contour plots for encapsulation effi-ciency as the response value were manifested in Fig. 1. Theoptimum process conditions identified by the results of responsesurface analysis (Fig. 1) and the aid of Design the expert 7.0 werethat the wall material concentration 1.0%, the rate of core and wallmaterial 1.25:1 and pH 4.2. The actual embedding rate is proved tobe 85.32%� 0.63%, while the theoretical value is 86.41%.

Fig. 3. SEM micrographs of lutein microcapsule products obtained by two treatments spraypowder samples was observed at 3000 and 6000 magnification times. The surfaces of spra

3.2. Results of physicochemical property study

The assessment of physicochemical properties of microcapsulesincluding size distribution, water content, fluidity appearance, ther-modynamics properties, etc. is a basic method to appraise productquality, an auxiliary means for technique optimization as well as animportant theoretical foundation for choice of storage conditions.

drying and freeze drying. After the dry procedure, the surface morphology of producty-dried products were smooth while the freeze dried product surfaces were wrinkled.

0

0.2

0.4

0.6

0.8

1

1.2

010002000300040005000

wavenumber/cm-1

abso

rpti

on i

nten

sity

0

0.2

0.4

0.6

0.8

1

1.2

-5005001500250035004500

abso

rptio

n in

tens

it

a

b

X.-Y. Qv et al. / Food Hydrocolloids 25 (2011) 1596e1603 1601

3.2.1. Water content rate, size distribution and morphologyThe rate of water content is 3.12% in a relative low level,

advantageous to the prevention against mildewing and oxidation.The results shown in Fig. 2(a) demonstrated that freeze driedparticles had a broad distribution in the size range of 0e30 mm andhad the biggest distributional proportion in the range of 10e20 mm,indicating homogeneous microcapsules produced under theoptimum condition. Their mean diameter was 14.198 mm. Fig. 2(b)is the size distribution of spray-dried products. By contrast, spray-dried products had a better homogeneity and integrity. Besides,Fig. 3 demonstrated that products treated by spray drying hada spherical appearance and a smooth surface, while the surface offreeze-drying capsules had typical folds and slight cracks due to theloss of water content during the freeze-drying process (Kim et al.,2008; Kwok, Groves, & Burgess, 1991).

3.2.2. Determination of product liquidityThe criteria suggested by Carr (1970) for assessing flow function

by static repose angle is that the angle lower than 30� is consideredgood fluidity, 30e45� some cohesiveness, 45e55� true cohesive-ness, while the angle beyond 55� indicates high cohesiveness andpoor flowability. The angle of repose examined in our experiment is37.1� (between 30� and 45�) signifying a good fluidity. The appli-cation value of microcapsules can be decreased by the poor fluiditythat is closely associated with coating material properties. Most offilm materials used in the preparation are colloids with a stronghygroscopic ability which affects product liquidity combined withthe usual chinks on the unsmoothed microspherical surface due tothe increase of friction. Additionally, the small-sized particles willalso reduce the liquidity because of more surfaces offered forparticle-particle interaction (Xu, Yao, Han, & Shao, 2007).

3.2.3. DSC analysis of lutein productDSC thermogram (shown in Fig. 4) demonstrated a quite

obvious turning point occurred at the starting of phase change withT0 (characteristic temperature) at 31.96 �C, Tc (final temperature) at47.15 �C, and Tg (peak temperature) at 40.52 �C (DH¼ 226.3 J/g).

The glass transition relates to the phenomena observed whena supercooled, malleable liquid or rubbery material is changed intoa disordered solid glass upon cooling, or conversely when a brittleglass is changed upon heating into a supercooled liquid ora rubbery material (Roudaut, Simatos, Champion, Contreras-Lopez,& Le Meste, 2004). The product may be shelf stable when stored

Fig. 4. DSC analysis of microcapsules containing lutein for the determination of glasstransition temperature. The DSC curves were recorded during the heating process withthe rate of 5 �C/min. The temperature 40.52 �C at the turning point is the vitrificationtemperature higher than room temperature.

below glass transition temperature since deterioration due tomicrobial growth and chemical reaction is greatly reduced (Sablani,Kasapis, & Rahman, 2007). Wall materials at vitrification temper-ature possess small permeability, which is helpful for preventingoxygen entry and beneficial to the preservation of core materials. Ifthe storage temperature is set higher than the vitrificationtemperature, because of the increase in internal mobility of reac-tants and diffusivity to oxygen, various chemical reactions are alsoaccelerated in dried products (Bhandari & Howes, 1999). Thevitrification temperature assayed was 40.52 �C, higher than roomtemperature. Consequently, products appeared stable when kept atnormal temperature.

wavenumber/cm-1

0

0.2

0.4

0.6

0.8

1

1.2

-5005001500250035004500

wavenumber/cm-1

abso

rptio

n in

tens

it

c

Fig. 5. Comparison analysis of the infrared spectroscopy of (a) gelatin, (b) gum arabicand (c) microcapsule to reveal if there exist newly generated chemical bonds betweengelatin and gum arabic. Before the analysis by using the infrared instrument at thewavenumber 500e4000, the three samples were separately grinded with a certainamount of potassium chloride. By comparison, it is verified that the interactionbetween gelatin and gum arabic was based on electrostatic force.

X.-Y. Qv et al. / Food Hydrocolloids 25 (2011) 1596e16031602

3.2.4. Infrared spectrum analysis of gelatin, gum arabicand microcapsule

The infrared spectrums of gelatin, gum arabic and lutein loadedmicrocapsule were shown in Fig. 5. The peak values of particlesfrom complex coacervation approximated those peak values of gumarabic at the wave numbers of 3032.82, 2825.15, 1587.51, 1475.52,1081.03, 627.21, respectively, showing gum arabic present incapsules. Also, gelatin existed in products as the peak values areapproximate at the wave numbers of 3082.57, 2822.34, 1627.21,

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 5 10 15 20 25 30time (day)

rete

ntio

n ra

te (

%)

microcapsule at 33% relative humidity

lutein at 33% relative humidity

microcapsule at 80% relative

lutein at 80% relative humidity

A

0.5

0.6

0.7

0.8

0.9

1

0 5 10 15 20 25 30

time (day)

rete

ntio

n ra

te (

%)

microcapsule in darklutein in darkmicrocapsule in lightlutein in light

B

0.7

0.75

0.8

0.85

0.9

0.95

1

0 5 10 15 20 25 30

time (day)

rete

ntio

n ra

te (

%)

microcapsule at 4°C

microcapsule at 25°C

microcapsule at 50°C

C

Fig. 6. The stability assessment of lutein in microcapsule product with relativehumidity, light, temperature and oxygen as four influential factors. (A) Effect of relativehumidity on the stability of lutein microcapsules. (B) Effect of light on the stability oflutein microcapsules. (C) Effect of temperature on the stability of lutein microcapsules.(D) Effect of oxygen on the stability of lutein microcapsules.

1512.33, 1465.54, and 1237.58, respectively. No generation of newchemical bond evidenced by no specific peak value found betweenspectrums of microcapsules and wall materials, further confirmsthe formation of complexes promoted by physical interaction suchas electrostatic interaction rather than chemical reactions (Yan, Ke,Dong, Ding, & Li, 2007).

3.3. Appraisal of lutein microcapsule stability

3.3.1. Effect of relative humidityRelative humidity is taken as a significant factor influencing

product storage. Both of gelatin and gum arabic have stronghygroscopicity, when placed in high humility environment,promoting the increase of water content in products and theconsequent gradual loss of lutein and structural collapse ofcapsules. The results (Fig. 6(a)) showed that after 30 days storagewith 33% relative humidity, the lutein retention rate of productswas 90.16% whereas the proportion of the non-encapsulated luteinwas just 68.18%. When kept in 80% relative humility for 30 days, theretention rates of the encapsulated and non-encapsulated luteinwere 68.18% and 30.15 respectively. It demonstrated that theproducts should be preserved in low relative humidity conditions.

3.3.2. Effect of lightAs is known, the light exerts destructive influences on lutein.

The results (Fig. 6(b)) suggested microencapsulation was anadoptable method to protect lutein against light effects. Theretention rates of lutein and its product were 71.16% and 80.16%when preserved in dark for 30 days, and 63.16% and 74.16% whenstored with light for 30 days.

3.3.3. Effect of temperatureThe temperature has remarkable effects on those heat-sensitive

bioactive substances. The retention rate of lutein decreases with therise of temperature. As is shown in Fig. 6(c), at the end of preser-vation for 30 days, the retention rates of lutein in products were92.86% at 4 �C, 90.16% at 25 �C and 73.63 �C at 50 �C. There was anobvious decline of stability at 50 �C. The main reason is that thetemperature 50 �C beyond the vitrification temperature 40.5 �Cmakes the system lose the glass state and promotes molecularchains to act drastically, reducing the stability.

4. Conclusion

The optimum process conditions determined by responsesurface analysis were as follows: CWM1.0%, RCW1.25:1 and pH 4.2.Under the condition, the theoretical encapsulation efficiency is86.41%, while the verified practical value is 85.32%� 0.63%. Theparticles had a broad distribution in the range of 0e30 mm, and heldthe biggest proportion in the range of 10e20 mm. The encapsulationeffectively enhanced the product stability from four aspects. Theproducts stored in normal temperature can sustain stability due tothe vitrification temperature 40.5� higher than the normal, and hadthe retention rate of 92.86% at 4 �C, 90.16% at 25 �C after 30 daypreservation. The ability to resist the impacts of light and temper-ature had also been improved. The retention rates were 90.16%withthe relative humidity of 33%, 90.25% with the preservation inoxygen, and 74.16% with the storage in light, respectively.

Acknowledgments

This project was supported by National Key Technology R&DProgram 2006BAD27B04.

X.-Y. Qv et al. / Food Hydrocolloids 25 (2011) 1596e1603 1603

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