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.

www.ttp.net(ID:123.15.50.26.21/05/12/05.29.38 )

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.

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