Effects of inorganic salt ions on long-term retrogradation characteristics of lotus seed starch under microwave treatment

The effects of inorganic salt ions (Na/K/Mg/Ca/Cu) on the long-term retrogradation characteristics of lotus seed starch (LS) under microwave treatment were investigated in this study. Compared to native starch, the dielectric properties of LS with the addition of inorganic salt ions for microwave treatment (LS-MW-Na/K/Mg/Ca/Cu) were significantly improved, indicating that their microwave energy conversion ability were significantly improved. LS-MW-Mg/Ca/Cu reduced signal intensity and the number of free radicals compared to LS-MW-Na/K. LS-MWNa/K decreased rapidly the mobility of free water, destroyed the hydrogen bonding between starch-starch and starch-water molecules, inhibiting starch retrogradation. Moreover, LS-MW-Mg/Ca enhanced the quantity of immobile water and exhibited the opposite effects in terms of the hydrogen bonding. There is an inflection point in the effect of LS-MW-Cu on starch retrogradation under microwave treatment. These results greatly enhance our understanding of the regulatory role of inorganic salt ions in the starch retrogradation under microwave processing and promote the design of starchy products with customized retrogradation properties.