Freeze-thaw pretreatment improved the anti-digestibility and viscosity of corn starch/type-A gelatin complexes

Slowly digestible starches, known to confer health benefits, are often prepared via compounding with other substances. However, starch complexes often encounter problems such as low viscosity. This work aimed to develop a corn starch/type-A gelatin (CS/GA) complex that simultaneously exhibited rapidly digestible starch (RDS) reduction, and superior viscosity. The pH and drying temperature of the complexes were systematically optimized, and a novel freeze-thaw pretreatment (FTP) technique was innovatively introduced. This work investigated the effects of varying FTP cycles (ranging from 0 to 8) on the physicochemical properties of CS/GA complexes. Results showed that FTP significantly enhanced the viscosity of the complexes while effective RDS reduction. Notably, after six FTP cycles, the complexes attained optimal properties, characterized by the highest the complex index (CI), relative crystallinity (RC) and short-range molecular order, accompanied by the lowest RDS reduction of 46.24 %. The multivariate analysis revealed CI as the crucial parameter for altering the resistant starch (RS) content. Furthermore, FTP induced cracking on the surface of starch particles was observed. In conclusion, these results were of significance for developing CS-based food materials with RDS reduction, and high viscosity characteristics, such as noodles, corn porridge and sausage.