The influence of freezing on the retrogradation of glutinous rice starch

Most glutinous rice food was stored under freezing, so it was necessary to study the retrogradation law of glutinous rice starch in frozen conditions for designing storage process.The experimental results showed that the minimum retrogradation rate of glutinous rice starch frozen for 1d increased from 4.5% to 15.7% when its concentration increased from 1% to 25%, from 4.7% to 32.6% when it was frozen for 7d.When the concentrations of glutinous rice starches were 1%, 5% and 25% respectively, the supercooled temperature in frozen storage lowers the retrogradation rate, the concentration of the glutinous rice starch milk should be away from the range of 10% ¹5% in the short-term refrigerated storage of glutinous rice food within 3d.Glutinous rice food should not be frozen in the refrigerator at-18℃, under these conditions for a week, the retrogradation rate of glutinous rice amylopectin became higher than 40%. A small amount of glutinous rice starch amylose would promote the amylopectin retrogradation.Electron microscopy images showed that glutinous rice starch was irregular block with above 6sides and most surface diameter of the granules was about 1 ~ 2μm, each surface section was flat. The shape of retrograded glutinous rice starch was adhesive layer structure.The shape of glutinous rice amylopectin was like jelly without regular shape. The retrograded glutinous rice amylopectin had obvious layered structure and its layer spacing was less than 1μm.