Abstract:Taking high-starch sweet potato as raw material，this paper studied the effects of starch concentration，pH value，press-heating temperature，press-heating time，and cooling time on the yield of resistant starch type 3（RS3）by single-factor experiments.Response surface methodology（RSM）was used to optimize the preparation conditions to improve the yield of RS3.The results showed that the optimal preparation conditions of RS3 were 13% of the starch concentration，pH5.5，110℃ of pressure heating temperature and 35 min of pressure heating time.Under suc conditions，the yield of RS3 was 37.94%，which was only 0.92% different from the predicted value，and the response surface model fitted well with the actual situation.Studies on in vitro anti-digestion characteristics of RS3 showed that the hydrolysis rate of RS3 and the digestibility of simulated digestive tract were low，and RS3 had strong resistance to enzymatic hydrolysis and anti-digestion.The results of electron microscopy showed that RS3 particles were irregular and lumpy with uneven surfaces，and the crystalline granular starch RS3 was mainly type B.The degree of particle order decreased，the degree of double helix and crystallization increased，and the structure became more compact as compared with the original starch.These structural properties explained the anti-digestion characteristics of RS3.