Optimisation of the reaction conditions for the production of cross-linked starch with high resistant starch content

•The cross-linking conditions were optimised using response surface methodology (RSM).•Reaction pH had a greater influence than temperature on RS4 type starch formation.•Wheat starch had better cross-linking ability than corn starch. The optimum reaction conditions (temperature and pH) for the preparation of cross-linked (CL) corn and wheat starches with maximum resistant starch (RS) content were investigated by using response surface methodology (RSM). According to the preliminary results, five levels were selected for reaction temperature (38–70°C) and pH (10–12) in the main study. RS contents of the CL corn and wheat starch samples increased with increasing temperature and pH, and pH had a greater influence on RS content than had temperature. The maximum RS content (with a maximum p value of 0.4%) was obtained in wheat starch cross-linked at 38°C and pH 12. In the case of CL corn starch, the optimum condition was 70°C and pH 12. CL corn and wheat starch samples were also produced separately under the optimum conditions and their RS contents were 80.4% and 83.9%, respectively. These results were also in agreement with the values predicted by RSM.