Preparation, physicochemical properties, and in vivo digestibility of thermostable resistant starch from malic acid-treated wheat starch.

In this study, malic acid treatment under different conditions, including molarity level (2-4 M), temperatures (90-130 °C), and time (2-12 h), was evaluated to prepare a modified wheat starch that is rich in resistant starch (RS). The physicochemical characteristics of the modified starch were also investigated. The application of 4 M malic acid and a heat treatment at 130 °C for 7 h produced a malic acid-treated (MT) wheat starch composed of 99.5 % RS. Fourier-transform infrared spectroscopy of MT wheat starch displayed a distinct carbonyl peak at around 1,740 cm, is formed due to the stretching vibration of the CO bond of the ester group. The crystalline and double-helix structures of the MT wheat starch were extensively destroyed, resulting in its enhanced degree of substitution, number of cross-linking bonds, and thermostable RS content (99 %) as well as its reduced viscosity. Furthermore, its consumption in vivo reduced the blood glucose level and response. The starch modification method reported herein could be applied when preparing RS-rich wheat starch for use in the production of heat-processed foods with high fiber contents and low calories.