Physicochemical and digestible properties of corn starch/gelatin complexes: Effect of pH, type of gelatin, and gelatin/starch ratio

Reducing the starch digestibility is particularly important for the prevention of obesity, diabetes and other related diseases. This work evaluated the effects of type-A gelatin (GA) or type-B gelatin (GB) of different ratios (12.5%, 25.0% and 50.0%, gelatin/starch, w/w) on the in vitro digestibility of corn starch (CS) at pH 4.0, 5.0 and 6.0. The complexation of CS and gelatin was electrostatic interactions and hydrogen bonds. The gelatin addition increased the turbidity of the system, the gelatinization temperature of CS, decreased the rapidly digestible starch (RDS) content, crystallinity, gelatinization enthalpy and viscosity of CS, and embedded within the internal CS matrix. At the same pH, the RDS content decreased with the increase of GA/CS or GB/CS ratio except for the TS -25.0%GA sample at pH 4.0. Ranked in order of RDS content, the pH values of the complexes were generally as follows: pH 5.0 > pH 6.0 > pH 4.0. Compared to GB, GA significantly reduced RDS content of CS under the same gelatin/starch ratio and pH conditions. The TS-25.0%GA complex exhibited the lowest RDS content of 56.36% at pH 4.0. These results will help to learn more about the mechanism of interaction between CS and gelatin, as well as the development of low content RDS corn starch-based food.