Whey protein isolate as a modifier of texture and digestibility in ready-to-eat corn paste.

Corn paste is widely consumed worldwide, but starch pastes often suffer from poor texture and lumping during hot-water reconstitution. This study introduces whey protein isolate (WPI) to regulate protein-starch-water interactions and improve rehydrated corn paste quality. WPI was added before or after extrusion to evaluate its effects on physicochemical, rheological, and nutritional properties. Pre-extrusion addition of 3% WPI significantly enhanced texture, water and oil absorption, and reduced solubility and bulk density. Microstructural analysis showed smoother surfaces and the disappearance of serrated cross sections. X-ray diffraction (XRD) confirmed A + V-type crystalline structures after extrusion. Rheological results indicated a shift from an elasticity-dominated to a viscosity-dominated system, improving dispersion and reconstitution. Nutritionally, pre-extrusion WPI protected tea polyphenols during digestion and reduced estimated glycemic index (eGI) by 10-15%. These findings support the use of pre-extrusion WPI to develop protein-fortified, relatively low-GI instant corn paste products.