Positively charged components (chitosan most potently) combined with annealing: Modulating digestibility and viscosity of corn starch

Starch complexation with non-starch components can reduce starch digestibility, which is crucial for increasing resistant starch (RS) content. However, the accompanying decrease in starch viscosity limits its application in food products. Annealing is a safe and environmentally friendly physical modification method. In this study, we systematically investigated the effects of adding different concentrations (1.0%, 2.0%, and 3.0%) of ε-polylysine (ε-PL), type-A gelatin (GA), chitosan (CS), and chitooligosaccharides (COS) combined with annealing treatment on the digestibility and viscosity of natural corn starch (NS). The results showed that the addition of these positively charged components (PCC) decreased the digestibility of NS, while exerting varying effects on the viscosity. Turbidity and Fourier transform infrared (FTIR) spectroscopy results showed that electrostatic attraction and hydrogen bonds were involved in the interaction between the PCC and NS during the annealing treatment. Furthermore, the formation of complexes was confirmed by the results of laser particle sizing, fluorescence microscopy, and scanning electron microscopy. Among the tested PCC, only CS effectively increased the viscosity of the complexes; moreover, CS increased the RS content more effectively than other PCC. The results may provide new insights into how NS/PCC interactions affect the digestibility and viscosity of NS.