The Study on the Mechanism of Improving Retrogradation Rate of Potato Starch by Yeast Fermentation on Raw Starch

Potato starch as raw materials, the effects of yeast fermentation on retrogradation rate by fermenta-tion are studied by determining retrogradation rate of potato starch. The reasons for increase of potato starch ret-rogradation rate are discussed based on visible and infrared absorption curve of potato starch before and after fermentation. The results show that the fine yeast fermentation of potato starch can make potato starch retrograda-tion rate rise from 12% to 39.4%, 2.28 times higher. The maximum visible absorbance wave length of amylose in fermented retrograded potato starch was 587.8 nm,higher than that of retrograded potato starch without fermentation, 569.6 nm. There were two reasons for improving of retrogradation rate of potato starch by yeast fermentation:first, the amylopectin of potato starch turns to amylose by debranching enzyme produced in the fermentation pro-cess, which increased the amount of amylose involved in retrogradation, second, aldehyde of potato starch was transformed into carbinol and further changed to glycosidic bond, which increased the chain length of amylase and promoted the process of crystal growth of starch retrogradation.