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: [email protected] (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:[email protected]://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:[email protected]://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.2012.02.0277/28/2019 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.
Top Related