7/28/2019 La deshidratacin de la protena cruda de Ginkgo biloba L. por congelacin secado por microondas

1/3

International Journal of Biological Macromolecules 50 (2012) 10081010

Contents lists available at SciVerse ScienceDirect

InternationalJournal ofBiological Macromolecules

journal homepage: www.elsevier .com/ locate / i jb iomac

Short communication

Dehydration ofcrude protein from Ginkgo biloba L. by microwave freeze drying

Liuping Fan a, Shaodong Ding a, Yuanfa Liu a,, Lianzhong Ai b

a State Key Laboratory of Food Science andTechnology, School of Food Science andTechnology, Jiangnan University, Wuxi 214122, Chinab State KeyLaboratory of Dairy Biotechnology, Technology Center, BrightDairy& Food Co. Ltd., Shanghai 200436, China

a r t i c l e i n f o

Article history:

Received 14 February 2012

Accepted 22 February 2012

Available online xxx

Keywords:

Ginkgo biloba L.

Protein

Microwave freeze drying

a b s t r a c t

The paper optimized the parameters of microwave freeze drying (MFD) of crude Ginkgo biloba protein

(CPG) using response surface methodology (RSM) based onthe analysis ofits proximate composition. The

results showed that coefficients ofdetermination, R

2

values for drying time and protein solubility weregreater than 0.9500. The drying time and protein solubility ofCPG varied curvilinearly with increase of

microwave power and pre-freeze temperature, and drying time varied linearly with material thickness.

The optimum MFD condition was microwave power of 408421 W, material thickness of 15mm and

pre-freeze temperature of20 C to 21 C, respectively.

2012 Elsevier B.V. All rights reserved.

1. Introduction

Numerous techniques can be used to dry solutions of proteins

andobtainproteinpowderswith desirablecharacteristics[1]. How-

ever, the most widely used techniques to dehydrate proteins are

vacuum freeze drying (FD). The FD dehydration can minimize the

losses of active components of foods owingto lowtemperature andlow absolute pressure [2]. In the other hand, FD is also recognized

as an expensive technology, because it requires much energy. The

costs are 48 times higher compared to air drying [3].

There are lots of researches related to reducing FD costs by

improving heat and mass transfer [4,5]. Among these improve-

ments, MFD appears to be one of the most promising techniques

to accelerate the rate of dehydration and enhance overall quality.

When applied to the FD process, microwave energy can penetrate

very well into ice and reduces the drying time by as much as 75%

[6]. Recently, MFD has been used successfully for drying beef, skim

milk, cabbage et al. [79].

Ginkgo biloba L. (usually called ginkgo) can date back to 200

million years ago and is considered as a living fossil. The proteins

of ginkgo with special biological activity have attracted extensiveattention [1012]. These researches indicated that Ginkgo biloba

seed proteins exhibited favorable bioactivity, and could be applied

in the food industry as functional additives. However, few of stud-

ies have been conducted on the effects of drying methods on the

characteristics ofGinkgo seeds protein. The purpose of this paper

is to optimize the microwave freeze drying parameters of crude

protein powders fromGinkgo biloba.

Corresponding author. Tel.: +86 0510 85876799.

E-mail address: fanliuping@jiangnan.edu.cn (Y. Liu).

2. Materials and methods

2.1. Materials

TheGinkgo biloba L. cvDafozhi seeds were purchasedfrom Taix-

ingof Jiangsuprovince (China).All reagentswere of analytical grade

and purchased from Sinopharm Chemical Reagent Co., Ltd (China).All results represent the average of duplicate determinations.

2.2. Chemical composition analysis

Protein content was calculated from the nitrogen content

(%N6.25) analyzed by Kjeldahl method. Water and fat con-

tent were determined by the official method of AOAC. Total

sugar content was examined using phenolsulfuric acid colori-

metric method. The polyphenol content was measured by the

FolinCiocalteau method.

2.3. Extraction of protein from Ginkgo biloba L. seeds

Crude Ginkgo seed protein (CPG) was obtained by an alkaline

dissolving and acid precipitating method [13]. The defatted flour

ofGinkgo biloba L. was dispersed in distilled water (10%, w/v), and

the pH was adjusted to 9.0 using 1M NaOH. The suspension was

stirred for 30min at room temperature, and then centrifuged at

6000g for 15min. The extracts were combined and acidified to

pH 4.4 with 1M HCl, and then left to stand for 30min to separate

into two layers. The precipitates were recovered by centrifugation,

then neutralised by 1.0 M NaOH to pH 7.0 and dialysed in distilled

water for 24h. The neutralised precipitate was dried using MFD.

0141-8130/$ seefrontmatter 2012 Elsevier B.V. All rights reserved.

doi:10.1016/j.ijbiomac.2012.02.027

http://localhost/var/www/apps/conversion/tmp/scratch_8/dx.doi.org/10.1016/j.ijbiomac.2012.02.027http://localhost/var/www/apps/conversion/tmp/scratch_8/dx.doi.org/10.1016/j.ijbiomac.2012.02.027http://www.sciencedirect.com/science/journal/01418130http://www.elsevier.com/locate/ijbiomacmailto:fanliuping@jiangnan.edu.cnhttp://localhost/var/www/apps/conversion/tmp/scratch_8/dx.doi.org/10.1016/j.ijbiomac.2012.02.027http://localhost/var/www/apps/conversion/tmp/scratch_8/dx.doi.org/10.1016/j.ijbiomac.2012.02.027mailto:fanliuping@jiangnan.edu.cnhttp://www.elsevier.com/locate/ijbiomachttp://www.sciencedirect.com/science/journal/01418130http://localhost/var/www/apps/conversion/tmp/scratch_8/dx.doi.org/10.1016/j.ijbiomac.2012.02.027

7/28/2019 La deshidratacin de la protena cruda de Ginkgo biloba L. por congelacin secado por microondas

2/3

L. Fanet al. / International Journal of Biological Macromolecules 50 (2012) 10081010 1009

Table 1

Thecoded values of theindependentvariables.

Variable Codes

1 0 1

X1 (W) 350 400 450

X2 (mm) 10 15 20

X3 (C) 25 20 15

2.4. Drying experiments of CPG

Experiments were carried out in a lab-scale microwave freeze

dryer (YT2S-01, Nanjing Yatai Microwave Power Technology

Research Institute, China). Before microwave freeze drying (MFD),

CPG was first frozen for 24h. During MFD, the pressure was main-

tained at 100 Pa by a vacuum pump, and the cold trap temperature

(40to45 C) was lowenoughto condense vapor. Themicrowave

frequencywas 2450MHz andthe power could be regulatedcontin-

ually from 0 to 2000W.

2.5. MFD optimization of CPG

A RSM was used to optimize the MFD whilst taking short drying

time and retaining high solubility of CPG. The three independent

variables in this experiment were microwave power (X1), material

thickness(X2) and pre-freezetemperature (X3). Thetwo dependent

variables were the drying time (Y1) and protein solubility (Y2). The

coded values of the three independent variables are summarized

in Table 1.

2.6. Properties analysis of CPG by MFD

Drying time was determined according to the moisture content

of the samples which dropped to 5% on the wet basis.

For the protein solubility test, CPG of 1% was dispersedin phos-

phatebuffer of pH 7.0at room temperature.The protein suspension

was stirred usinga magnetic stirrer for60 minataspeedof500rpm

and were centrifuged at 6000g for 30min. The soluble protein

content in the supernatant was determined by Kjeldahl method.

2.7. Statistical analysis

Data were analysed by using the Statistical Analysis System

(SAS, version8.0, SAS Institute Inc.,Cary, NC,USA).Analyses of vari-

ance were performed by the anova procedure. Mean values were

considered significantly different whenp< 0.05.

3. Results and discussion

3.1. Proximate composition

The proximate composition results of the de-hulled Ginkgo

biloba L. cv Dafozhi showed that water was the dominant compo-

nent (48.361.89% in wet basis), followed by starch and protein

with71.381.27% and 11.570.16% in drybasis, respectively. The

protein content of sample was in agreement with the reports by

Deng et al. and they found that there is 913% crude protein (dry

basis) in Ginkgo biloba seed [10]. The protein content is high on a

dry matter basis, which makes Ginkgo biloba a good supplement

to protein resource. Low contents of lipid (5.450.43%, d.b.), total

sugar (3.170.18%, d.b.) and total phenolic (3.210.15, d.b.) were

found in de-hulledGinkgo biloba L. sample.

Table 2

The results of response surface analysis of the variation of drying time (Y1 ) and

solubility (Y2) with microwave power (X1), material thickness (X2) and pre-freeze

temperature (X3).

Run Coded variables Drying time (h) Solubility (%)

X1 X2 X3

1 1 1 0 8.8 48

2 1 1 0 11.2 50

3 1 1 0 4.4 56

4 1 1 0 5.2 55

5 0 1 1 4.9 48

6 0 1 1 8.3 60

7 0 1 1 7.3 59

8 0 1 1 10.1 57

9 1 0 1 10.5 53

10 1 0 1 4.5 52

11 1 0 1 11.9 50

12 1 0 1 10.1 59

13 0 0 0 5.4 67

14 0 0 0 5.9 66

15 0 0 0 5.3 66

3.2. Process optimization

The coded values of the three independent variables and theresults are summarized in Table 2. Results revealed that the drying

time of CPGvaried from 4.4h to 11.9 h,solubility of CPGvaried from

48% to 67%. Data were analyzed by the SAS multivariate regression

program and could be fitted to the following equation.

Y = b0 + b1x1 + b2x2 + b3x3 + b11x21 + b22x

22 + b33x

23 + b12x1x2

+b13x1x3 + b23x2x3 (1)

The regression coefficients and analysis of variance of CPG are

listed in Table 3. The high coefficients of determination R2 (0.9875

and 0.9751) indicated that the variables were adequately fitted to

the regression equation. The probability (p) values of all regression

models were less than 0.01. The coefficient of variation (CV) is the

ratioof the standarderrorof estimateto the mean valueof observed

response expressed as a percentage. It is a measure of reproducibil-

ity of the models. The CV of the model was calculated as 6.6% and

3.01%, respectively. As a general rule, a model can be considered

reasonably reproducible if its CV is not greater than 10% [14].

3.3. Effects of MFD on the drying time

The drying time (Y1) of CPG was significantly (P< 0.05) affected

by the linear terms ofX1, X2 and X3, interact terms ofX1X3 and

Table 3

Regression coeffcients, R2 andp values forthe response function (Eq. (1)).

Coefficient Y1 (drying time) Y2 (solubility)

b0 5.53 66.33

b1 2.28c 2.63b

b2 0.93b 1.13

b3 1.65c 1.75a

b11 1.73b 8.29c

b22 0.13 5.79b

b33 1.98c 4.54b

b12 0.4 0.75

b13 1.05b 2.5a

b23 0.15 3.5b

R2 0.9875 0.9751

CV 6.60 3.01

P 0.0003 0.0017

a Significant atp

7/28/2019 La deshidratacin de la protena cruda de Ginkgo biloba L. por congelacin secado por microondas

3/3

1010 L. Fanet al. / International Journal of Biological Macromolecules 50 (2012) 10081010

Fig. 1. The contour plots of the drying time and solubility of CPG as affected by

microwave power and pre-freeze temperature (material thickness 15 mm).

quadratic terms ofX12 andX3

2. The drying time linearly increased

with increasing material thickness and varied curvilinearly with

pre-freeze temperature, and this may be related to the penetra-

tion depth of microwave. The shorter drying time was observed at

the pre-freeze temperature from22 C to20 C. Bothmicrowave

power and pre-freeze temperature exerted a quadratic effect on

drying time. The drying time dramatically declined with increas-

ing microwave power. This result was in agreement with that of

Abbasi [5] and thedrying process acceleratedowing to highermass

transfer rate and vapour pressure difference between the central

and the external parts of the products. When the CPG was dried

at the microwave power more than 400W and material thick-

ness lower than 15mm, drying time will be shortened to less than5 h.

3.4. Effects of MFD on the solubility of CPG

The protein solubility (Y2) of CPG was significantly (P< 0.05)

affected by the linear terms ofX1, X3, interact terms ofX1X3, X2X3and quadratic terms ofX1

2, X22 and X3

2. Material thickness did

not seem to affect protein solubility in the selected range whereas

microwave power exerted a significant effect. CPG has the higher

solubility at the microwave power of 394421 W. The loss of sol-

ubility of CPG in high-power microwaves can be attributed to the

protein denaturation under higher temperature. Deng et al. found

the total contents albumin and globulin were 90.8% inGinkgo seed

protein isolate [10]. However, the albumins and globulin appeared

as the most readily denatured proteins and their solubility index

dropped significantly as the drying temperature increased [15,16].

Theloss of solubility in low-powermicrowaves canbe attributed to

the long drying time and this result was in agreement with that of

Joshi et al. [15]. Bothmicrowave power and pre-freezetemperature

exerted a quadratic effect on protein solubility of CPG. The results

indicated that the medium concentration in microwave power and

pre-freeze temperature extracted higher solubility of CPG. The sol-

ubility could be above 66% when the material thickness was fixed

at 15mm, microwave power varied from 393 W to 422 W and pre-

freeze temperature from21 C to17 C. The solubility increased

withincreasing material thicknessand pre-freezetemperature and

then decreased when material thickness was above 16mm and

pre-freeze temperature was below 20 C.

3.5. Optimum drying conditions for the higher solubility and

shorter drying time

By analyzing the effects of MFD conditions on the drying time

and solubility of CPG, the drying time and solubility changed sig-

nificantly with microwave power (X1) and pre-freeze temperature

(X3). Contour plot of both dryingtime andsolubility as a functionof

microwave power and pre-freeze temperature is shown in Fig. 1. It

suggestedthat optimum drying conditionwas microwave power of

408421W andpre-freeze temperature of20 C to21 C, respec-

tively suggested by the cross hatched area. The drying time and

solubility of CPG were expected to be about 5 h and 60%, respec-

tively.

Acknowledgements

This work was supported by the National Natural Science

Foundation of China (31101361), the National High Technology

Research and Development Program of China (2011AA100806-3)

and the Fundamental Research Funds for the Central Universities

(JUSRP211A30).

References

[1] M.J. Maltesen, M. van de Weert, Drying methods for protein pharmaceuticals,Drug Discov. Today: Technol. 5 (2008) e81e88.

[2] S. Kadoya, K. Fujii, K. Izutsu, E. Yonemochi, K. Terada, C. Yomota, T. Kawanishi,Freeze-drying of proteins with glass-forming oligosaccharide-derived sugar

alcohols, Int. J. Pharm.389 (2010) 107113.[3] J.M. Flink, Energy analysis in dehydration processes, Food Technol. 31 (1977)

7779.[4] Z.L.Wang, W.H.Finlay, M.S.Peppler,L.G. Sweeney,Powder formationby atmo-

spheric spray-freeze-drying, Powder Technol. 170 (2006) 4552.[5] S. Abbasi, S. Azari, Novel microwave-freeze drying of onion slices, Int. J. Food

Sci. Technol. 44 (2009) 974979.[6] T.K. Ang, J.D. Ford, D.C.T. Pei, Microwave freeze-drying of food: a theoretical

investigation, Int. J. Heat Mass Trans. 20 (1977) 517526.[7] Z. Wang, M.H. Shi, Microwave freeze drying characteristics of beef, Drying

Technol. 17 (1999) 433447.[8] X. Duan, M. Zhang, A.S. Mujumdar, Studies on the microwave freeze dry-

ing technique and sterilization characteristics of cabbage, Drying Technol. 25(2007) 17251731.

[ 9] W. Wang, G. Chen, F. Gao, Effect of dielectric material on microwave freezedrying of skim milk, Drying Technol. 23 (2005) 317340.

[10] Q.Deng, L. Wang, F. Wei, B.Xie,F. Huang, W. Huang, J.Shi,Q. Huang, B.Tian, S.Xue, Food Chem. 124 (2011) 14581465.

[11] J.Yang,C. Wu, Y. Li,S. Jia, G.Fan,F. Peng, Agric. Sci. China 10 (2011) 631641.

[12] W. Huang, Q. Deng, B. Xie, J. Shi, F. Huang, B. Tian, Q. Huang, S. Xue, Food Res.Int. 43 (2010) 8694.

[13] U.D. Chavan, D.B. McKenzie, F. Shahidi, Food Chem. 74 (2001) 177187.[14] E. Firatligil-Durmus, O. Evranuz, LWT Food Sci. Technol. 43 (2010) 226231.[15] M.Joshi, B. Adhikari, P. Aldred, J.F. Panozzo, S. Kasapis, Food Chem. 129 (2011)

15131522.[16] P.Malumba, S.Janas, T. Masimango, M. Sindic, C. Deroanne,F. Bra, J. Food Eng.

95 (2009) 393399.