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Study on technology of ultrasound-microwave assisted improves preparation of porous starch

 

 
Advanced materials research vols.476-478(2012)pp 744-750
Online available since 2012 Feb/27 at www.scientific.net
(2012) Trans Tech Publications Switzerland
Doi:10.4028/www.scientific.net/AMR.476-478.744
                               Study on technology of ultrasound-microwave assisted improves preparation of porous starch
Zhongdong Liu1,a,Yongmei Yang1,b,Hui Liang1,c,Lizheng Bi1,d
and Bengqian Gong1,e
1College of Food Science and Technology, Henan University of Technology, 450052,Zheng Zhou
aemail:liuzhongdong2345@163.com bemail:xjboy310@163.com
cemail:lh20064960333@163.com demail:bilizheng123@126.com
eemail:gongbenqian@yahoo.com.cn
 
Keywords:ultrasonic; microwave ; double enzyme coupled ; porous starch
 
Abstract:Porous starch as a kind of high efficiency, non-toxic and safe new organic adsorbents are extensively
used in food, medicine, agriculture, cosmetics, paper and other industries. Recently the preparation method is
amylase in starch gelatinization temperature of less than hydrolysis. In the conditions of ultrasound (physics) and
microwave (electromagnetic fields), we could improve the yield of the traditional method of enzyme hydrolysis
corn starch. First, the results show that: the time at 45 min, microwave power 150W, ultrasonic power 400W,
temperature 56℃, α-amylase enzyme quantity 8 U/g, glucoamylase and α-amylase ratio 6:1, citric acid buffer
liquid pH 5.4, the absorption rate of porous starch is best. Ultrasonic- microwave improves the quality of
customary enzymatic hydrolysis starch, by SEM observation, found that: There are a lot of table face holes which
are uniform pore density, particle more complete.
 
The starch is a semi-crystallize property polymer, under the polarizing microscopeobservation, they present to
cross-cross. Starch has tows kinds structure, crystallizing field and amorphous region. With the highly ordered
internal structure, it’s hard to react with enzyme and other chemical reagent [1]. So it could limit the reaction rate
and the quality of products.The porous starch is made by the physical method, mechanical method or biological
method, through making starch granules to be holes starch from surface to internal, like hornet’nest[2]. Mainly used for organic adsorption carrier. Due to its high efficiency, non-toxic, safety, biodegradability and other advantages, starch have widely application prospects in food, medicine, daily chemical industry, agriculture and other industries. Ultrasonic is a kind of involuntary vibration, the elastic medium frequency range of 105-108 Hz. Study found that in the role of starch, ultrasonic, can speed up the reaction rate, also can make the surface of the starch grain in different degrees of a honeycomb of depression and the whole [3].
 
Microwave used for the modified starch research began in 1924 J.K. corduroy etc. [4], using aqueous
enzymatic as the synthesis method of carboxymethyl starch for the first time. Microwave is a kind of
electromagnetic wave,which can heat reactants without heat conduction, can change reaction rate in the thermal
effect of the reaction from internal expansion, as well as between the behavior of electromagnetic fields on the
molecular response caused by the direct effect of the non-thermal effects, such as causing some chemical reaction dynamics changes and accelerating the speed of the catalytic effect of chemical reaction, causing polymer
molecules chain breaking and other biochemical effects and magnetic effects, increasing the chiral selectivity of
product characteristics [5-6].
 
At present, the conditions of ultrasonic- microwave under enzyme hydrolysis preparation porous starch have
not been reported. In this study, According to the oil absorption rate, under enzymatic hydrolysis of corn starch
with microwave-ultrasonic preparation of porous starch, it has determined the condition of supersonic affects the
compound enzyme reaction, and has explored an efficient, the green preparation porous starch new techniques.
all rights reserved. No part of contents of this paper may be reproduced in any forms or by any means without the written permission of TTP.
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1 materials and methods
1.1 The main materials and equipment
Corn starch: Henan Qixue Starch Co.,Ltd. ; Liquozyme Supra / 2.2 X amylase, Dextrozyme DX / 1.5: Novozymes
(China) Biotechnology Co., Ltd; Soybean oil: Yi Hai (Zhoukou) Grain and Oil Co., Ltd. ; XO-SM50
ultrasonic-microwave reaction system: Nanjing Xian’ou Instrument Manufacturing Co., Ltd.; SEM: Japan
HITACHICO. S-3400 NⅡ.
1.2 Method
1.2.1 The preparation of porous starch [7 -9]
Corn starch (30g) and pH 5.0 citric acid buffer liquid (150 mL) put into a 250ml special reaction kettle. The
mixture keep in water bath for 10 min at 55℃, then add appropriate dilution of 300μL α-amylase, 900μL
glucoamylase. After microwave-ultrasonic reaction system for 30min at 55℃, adding 4% NaOH solution 2.5 mL
to end reaction. The reaction liquid filter at vacuum pump, and distilled water repeated to wash the reaction kettle.
Then products will be dried at atmospheric pressure, and smashed (100 mesh).
1.2.2 Single factor experiment
Changing one of the starch concentration, reaction system pH, enzyme quantity of every gram starch, ultrasonic
power, microwave power, reaction temperature and reaction time, remained other factor unchanged to start single
factor experiment.
1.2.3 Pathogen orthogonal test
According to single factor experiment result, orthogonal test of L18(37) is designed, and obtaining the best
technological condition.
 
1.2.4 Determination of oil absorption rate
The oil absorption rate is that the quality of porous starch absorbs soybean oil/the quality of porous starch. Put 2.0g
of starch samples into a beaker, and stir 60min with the excessive oil mixed in shaker in the constant temperature,
then shift into filter funnel Buchner, use circulating vacuum pump water filter until oil drops. Record the weight
before and after the starch, and calculate the oil absorption rate.
1.2.5 Scanning electron microscope
Samples are placed under a scanning electron microscope, shooting the representative of the starch.
2 Results and Discussion
2.1 The determination of enzymatic activity [10]
Quantitative determination by DNS, α-amylase activity: 488.72U/mL, glucoamylase activity: 1289.90U/mL
 
2.2 Enzymolysis starch single factor test experiment
 
2.2.1 Enzyme solution of oil absorption rate of time influence
The figure 1 show that in the certain amount of enzyme, due to the number of holes starch, pore diameter and
the depth, the reaction time is too short, while oil absorption rate is low; if the reaction time is too long, due to the
collapse of the formation the holes and the lower activity enzymes, oil absorption rate of porous starch falls fast.
 
2.2.2The amount of enzyme quantity of oil absorption rate influence
By figure 2 show, the optimal dosage of enzyme in the starch is 9 U/g in experimental condition. At one time
oil absorption rate is highest. If to the amount of enzyme is less, hydrolysis of starch particles is not enough, and if
the amount of enzyme is more, hydrolysis of starch particles is excessive, then causes excessive starch particles
collapsed, so the oil absorption rate is not high.
Fig.
 
2.2.3 Reacting system pH to oil absorption rate influence
The figure 3 shows that both of the optimal PH of two kinds of enzymes is 5.4. Due to the complex enzyme
activity is higher than others in the acidic condition, at this time produced porous starch oil rate is highest,

 

2.2.4 Reaction temperature in the influence of oil absorption rate
The figure 4 shows that while other factors are not changed, different temperature has significantly different
influence in the porous starch oil absorption. When the reaction temperature ranges 55~58℃, the production
porous starch oil absorption rate is higher, the reason is the most suitable reaction temperature in this temperature
sector for the glucoamylase and α-amylase, and its activity is high.
Fig.
 
2.2.5Microwave power to the influence of oil absorption rate
The Figure 5 shows that, as the microwave power increases, oil absorption rate of starch also increases. When
microwave power reaches 160w later, microwave heating causes thermal effect of reactant is very serious, and then
the reaction liquid temperature rises very fast and out of control.
Fig.

 

2.2.6 Enzyme ratio to the influence of oil absorption rate
It can be seen from Figure 6 that, as increasing in the proportion of glucoamylase and reducing proportion of
α-amylase, the oil adsorption rate of porous starch will rises, then decreases. The reason is that starch
glucoamylase can be put outside the α-1, 4 - glycosidicbond and α-1, 6 - glycosidic bond to generate a β-glucose;
and α-amylase is the interior contact amylase, starch molecules within it from arbitrary cut α-1, 4 - glycosidic bond,
so that degradation of starch molecules are better effected by glucoamylase. The oil adsorption rate of porous
starch is max when oil rate changes along with the enzyme allocated a proportion at 6:1.
 
2.2.7 Ultrasonic power to the influence of oil absorption rate
In this experiment, ultrasonic launching device is set to clearance 3 seconds-3 works seconds condition.
Figure 7 shows that the ultrasonic in the 400W, the oil adsorption rate is highest. Follow with the increasing
power, oil absorption rate reduced instead. The reason is that the ultrasonic cavitation intensity is affected by
ultrasonic power because of the influence of the change, low power ultrasonic cavitation effect as the high power
has obvious effect. Therefore the effect of supersonic cavitation is good in certain power range. In addition,
ultrasonic has also played the role of the mixing reaction liquid in the experiment
 
2.2.8 Starch density to oil absorption influence
Starch pulp density in 40% neighbor, oil absorptions is highest by Figure 8 demonstration. If Starch pulp
density is too high to fully react, oil absorption rate will decrease siginificantly; If Starch pulp density is too low,
porous starch is collapsed by lots holes, the oil absorption rate will also decrease sifinificantly.
 
2.4 SEM observation starch structure
The different hydrolysis of starch conditions, the different sizes porous holes on the starch granules, and very
different degrees of density. Compared with native starch, porous starch seems like honeycomb, the number of the
table face is more and density is uniform.The aperture is not big, the depth of hole is moderate, and the particle is
complete. The surface area increases and the rough surface adsorption of various liquid substances capacity
enhancement, so you can use oil absorption rate to determine the formation of porous starch situation.
 
3.Conclusions
Ultrasonic-Microwave combined with enzyme hydrolysis prepares high oil absorption rate corn porous starch.
Based on single factors research, optimize the corn starch preparation process conditions. The results show that:
the time at 45 min, microwave power is 150W, ultrasonic power is 400W, temperature is 56℃, α-amylase enzyme
quantity is 8 U/g, glucoamylase and α-amylase ratio is 6:1, citric acid buffer liquid pH is 5.4, the absorption rate of
porous starch is best.
Acknowledgement
Supported bythe NSFC: 11079019、31071606、11111120315、20811120358、20672629、30270762、
20911120202、29576263 and by the National High Technology Research and Development Program of
China:2007AA100401and Nanjing Xian’ou Instrument Manufacturing Co., Ltd.The authors thank SSRF and
NSRL for their kind help.