Study On Physicochemical Property Of Modified Rice Starch By Physics And Enzymatic

The purpose of this paper was to explore the effects of physical and enzymatic modification on the physicochemical properties of rice starch.The anti-enzymatic of raw starch was 1.29%. The results of physical modification experiments showed that the anti-enzymatic of rice starch modified under the conditions of 115℃ autoclaved 30 min,500W microwave heating,100W microwave heating and 25kHz single-frequency ultrasonic were 13.49%,12.69%,0.78% and 1.76%, respectively.The results of enzyme modification experiments showed that the anti-enzymatic of rice starch modified by thermostable a-amylase and pullulanase was 6.68%, and that of pullulanase debranched rice starch with the molecular weight above 30K was up to 13.47%.The results of composite processing modification experiments showed that the anti-enzymatic of starch modified with heating and enzyme was 12.42%. Ten percent of sodium ions and twenty percent of calcium ions could enhance the anti-enzymatic of starch to 11.30% and 26.54%, respectively. Although pectin could improve the anti-enzymatic of starch, adding pectin and calcium ions at the same time could reduce the anti-enzymatic of starch.The results of physicochemical properties determination of modified starch showed that all modification methods, except the methods of ultrasound treatment and 100W microwave treatment, could enhance the retrogradation of starch. The solubility and the swelling capacity of starch were increasing with the enhancing of treatment temperature. After modification, starch’s peak viscosity reduced while their particle size increased. According to the results of DSC detection, autoclaving and 500W microwave treatment could enhance the To, Tp and Tm values of starch, but other modification methods could decrease the To, Tp, Tm and Δ H values. According to the results of scanning electron microscope observation, native starch presented angular polyhedron. The starch modified by autoclaving,500W microwave, pectin, calcium and sodium ions melted and showed no particles. Modified by 100W microwave, the particle surface edges and corners of starch became fuzzy slightly. There were signals of melting and burst holes one large granular starch surface. Ultrasonic treatment led to some holes on the surface of starch granules. Native starch was the type A crystal. Although ultrasonic and 100W microwave modification could not change the types of starch crystal, autoclaving,500W microwave, pectin, calcium and sodium ions treatments could change the starch’s crystal to V type.