Abstract:

In freeze-drying process, the heat transfer efficiency of high-starch fruit-vegetable juice is reduced due to its high viscosity. In this study, α-amylase was used to appropriately hydrolyze the starch in lotus seed powder to reduce its viscosity, improve the freeze-drying efficiency and explore the relationship between viscosity and rehydration. Based on the effects of hydrolysis time, hydrolysis temperature, pH and enzyme amount on the viscosity of lotus seed powder, the optimal enzymatic hydrolysis conditions were achieved by orthogonal experiments to be enzyme amount of 16.56 U/mL, hydrolysis temperature of 70 ℃, hydrolysis time of 15 min and pH 6.5. The viscosity of hydrolyzate was 77 mPa·s and its DE value was 4.95%. Four factors had a significant impact on results (P ＜ 0.01). At the same time, the viscosity of lotus seed powder was negatively correlated with the rehydration property. Therefore, enzymatic hydrolysis and freeze-drying had a significant influence on rehydration property (P ＜ 0.05).

Key words: lotus seed powder, α-amylase, viscosity, rehydration rate