Study on the Preparation and Digestibility of Malic Acid Sweet Potato Starch Ester under Microwave Assistance

Abstract

AbstractIn this paper, malic acid sweet potato starch ester (MSE) is prepared by the microwave assisted l‐malic acid method, and its digestibility is studied. Through a response surface methodology based on a Box‐Behnken design (BBD), the optimum conditions for the preparation of MSE are obtained as follows: mass ratio (mL‐malic acid: mstarch) of 0.81, pH value of 1.21, microwave time of 6.8 min, and microwave power of 435 W, respectively. Under these conditions, the degree of substitution of MSE is 0.0712. In addition, the freeze‐thaw stability, transparency, and solubility of the MSE are better than the native starch. Microwave assisted l‐malic acid treatment significantly increases the resistant starch (RS) content in starch sample. FTIR reveals a new characteristic peak near 1735 cm–1 in MSE samples, and the relative crystallinity decreases from 33.03% to 21.18%. Differential scanning calorimetry results show that the endothermic peak of MSE decreases. These results indicate that microwave‐assisted l‐malic acid can significantly change the physicochemical properties of sweet potato starch, and it is an effective method for the preparation of RS with heat‐stable resistance.