Manufacture of resistant starch by different physical modifications and storage times

Resistant starch is the starchy material that is not digested after being hydrolyzed in human’s small intestine, but would be fermented in colon. Therefore, the physiological functions of the resistant starch are analogous to the dietary fibers of polysaccharides, and are claimed to have many benefits to health. The manufacturing of resistant starch by physical modifications is safe, easy and cheaper than chemical modifications. It depends on a number of factors. Among them, amylose content, degree of gelatinization and storage time are the most important factors for formation of resistant starch. In this research, high amylose maize starch (amylose>50%) was used to investigate the effects of different physical modifications (hot plate, water bath, high pressure autoclave) and storage time (storage at 7°C for 7 and 14 days) on the resistant starch content. The difference of physical modifications, treatment time and storage time on the resistant starch content of high amylose maize starch were compared to establish the optimal conditions of physical modifications for resistant starch manufacturing. Results showed that higher amount of resistant starch would be produced by various physical modifications and storage time of high amylose maize starch. The resistant starch content of high amylose maize starch processed by different physical modifications without storage was 8.74-28.55%, which would be influenced by physical modifications and treatment time. Further, water bath and high pressure autoclave treatment showed higher resistant starch content than hot plate treatment with or without storage, and both showed that 1 h treatment had the highest resistant starch content without storage (24.58 and 28.55%), while treatment for 1 h by water bath or high pressure autoclave treatment are the most effective physical modifications for resistant starch manufacturing from high amylose maize starch. However, the resistant starch content of most samples significantly increased after storage. In addition, the high amylose maize starch processed by water bath for 60 min and storage for 7 days had the highest resistant starch content (32.72%), but that in some samples significantly decreased when extending storage time to 14 days. The analysis of resistant starch content average indicated that there’s no statistically significant difference in resistant starch content by using either the water bath or the high pressure autoclave treatment during storage. The results provide important information and index for the effective manufacturing of resistant starch for both research and commercial preparation.