| Starch is a cheap renewable organic raw material with abundant sources,but it has its own shortcomings,such as easy aging of starch paste,low emulsifying capacity,poor solubility in cold water,weak thermal stability and so on.Therefore,starch needs to be modified by physical modification,chemical modification,biological modification,composite modification and so on.As one of the physical modification,ultrasonic technology has its advantages,such as short treatment time,low energy consumption,safety,high efficiency and environmental protection.In this paper,corn starch(A-type crystal),potato starch.(B-type crystal)and pea starch(C-type crystal)were used as raw materials.The effects of ultrasonic power,ultrasonic frequency,ultrasonic time and ultrasonic temperature on the structure and physicochemical properties of starch were systematically studied by using fourier transform infrared,differential scanning calorimetry and rheometer.In order to provide a new method and idea for the comprehensive utilization of starch resources,and provide a theoretical basis for the ultrasonic physical modification of starch.The main results are as follows:(1)Different ultrasonic treatments reduced the amylose content of corn starch and pea starch,but increased the amylose content of potato starch.Polarizing microscope results showed that most of the three starch granules remained intact after different ultrasonic treatment,and there was no significant difference compared with the original starch.A small number of starch granules were broken due to the enhancement of ultrasonic effect,with obvious pits on the surface,and the polarizing cross became blurred or even disappeared.The measurement results of the micron particle size analyzer showed that the average particle size of corn starch increased from 14.37μm to 15.37 μm,the average particle size of potato starch increased from 37.67 μm to 59.76 μm,and the average particle size of pea starch increased from 26.05 μm to 39.18μm after different ultrasonic treatments.The results of infrared spectrum showed that the positions of the absorption peaks of the characteristic groups did not change and the chemical structure of the three starch were not changed.The results showed that the maximum value of 1047/102 2cm-1 and 995/1022cm-1 of corn starch increased to 1.66 and 2.76 respectively.The 1047/1022cm-1 of potato starch and pea starch decreased to 0.54 and 0.29 respectively,the maximum value of 995/1022 cm-1 was 0.90 and 0.70 respectively.(2)The results of thermodynamics showed that the gelatinization temperature,thermal stability and crystal difference of corn starch,potato starch and pea starch decreased under different ultrasonic treatments,△H decreased.The results of dynamic rheology showed that different ultrasonic treatments increased the storage modulus and loss modulus of the 3 starch pastes and increased the gel strength.The results of static rheology showed that 3 kinds of starch paste had shear thinning after different ultrasonic treatment,which belonged to pseudoplastic fluid,and the lag area of corn starch paste decreased,the recovery and stability increased,while potato starch paste and pea starch paste lagged area increased,recovery decreased,and the three-dimensional network structure of gel was rigid.The results of solubility and swelling test showed that the solubility and swelling of three starches were increased by different ultrasonic treatments.The gelatinization degree and retrogradation degree measurement results showed that different ultrasonic treatments increased the gelatinization degree of the three starches,the retrogradation degree of corn starch increased and then decreased,and the retrogradation degree of potato starch and pea starch decreased.(3)The results showed that the content of starch resistant starch was increased by 1.95%～10.79%by ultrasonic treatment,the digestibility of starch was reduced and the digestibility of corn starch was improved;The content of fast digested starch of potato starch was increased by 1.24%～12.98%,the content of resistant starch was 3.22%～19.26%,and the digestibility of potato starch was reduced;The content of slow digested starch increased by 0.73%～8.34%by ultrasonic treatment,which reduced the anti digestibility of starch.The results of Pearson correlation analysis showed that the content of resistant starch and amylose content of corn starch were significantly negative(p<0.05),the content of resistant starch and amylose content of potato starch were significantly positive(p<0.05),and that of pea starch was significantly positive correlation with amylose content(p<0.01);The content of fast digested starch of pea starch was negatively correlated with the average particle size(p<0.05).Under different ultrasonic power treatments,the content of potato starch fast digestible starch was significantly positively correlated with 995/1022 cm-1(p<0.01),and the content of pea starch fast digestible starch was significantly negatively correlated with 1047/1022 cm-1(p<0.01);Under different ultrasonic temperatures,the content of fast digestible starch of corn starch was significantly positively correlated with 1047/1022 cm-1(p<0.05),the content of slow digestible starch of potato starch was significantly positively correlated with grain size(p<0.05),the content of resistant starch was significantly negatively correlated with average grain size(p<0.05),and the content of slow digestible starch of pea starch was significantly positively correlated with 1047/1022 cm1(p<0.05),There was a significant negative correlation between resistant starch content and grain size(p<0.01). |
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