Studies On Retrogradation Of Instant Rice And Improvement Of Processing

This study mainly focused on retrogradation of instant rice and improvement of processing. The influence of water content, time, distributions of the chain lengths and amylases on retrogradation and sensory quality of instant rice were investigated in order to get the best processing and quality standard of instant rice.Firstly, in order to control retrogradation during storage, the degree of gelatinization was used to investigate the effects of water content, time, distributions of the chain lengths and amylases on retrogradation of instant rice. The results showed that the degree of gelatinization of sample with 60% water content had an obvious change after storage at 4℃for three weeks, and shortened the chain lengths of amylopectins can restrain retrogradation of it.Secondly, in order to control retrogradation and improve the sensory quality, effects of amylases on instant rice and processing were investigated with the degree of gelatinization and texture profile analysis (TPA). The result indicated that the effect of maltase on retrogradation of instant rice is the best among the three kinds of amylases, and at the same time, the maltase can also improve the texture character of instant rice a little. The best processing were that the cooking time was 25min, the concentration of maltase was 52mg/L, the time of soaking in solution of maltase was 15min, and time of soaking in solution with pH=4.3 was 2min.Finally, the samples were investigated with sensory evaluation, and the quality standard had been made. After a long time storage, the samples made with the best processing tasted better than the product of the same type salting in the market, although their sensory quality were also worse than the fresh cooked rice. The quality standard of product should contain the sensory indexes, physicochemical indexes and microbial indexes.