Harnessing metal-polyphenol networks (MPNs) to regulate the digestive kinetics and enhance gel properties of whey protein gel: The influence on intermolecular interaction force and microstructure

Whey protein (WP) has significant applications in the fields of food and nutrition. However, WP has the characteristics of fast digestion rate and a wide range of different gel properties depending on processing history, which limits its application in industrial production. Therefore, in this study, proanthocyanidins and calcium ions were introduced as model polyphenols and metal ions to form a versatile novel material, metal-polyphenol networks (MPNs). MPNs with strong adhesive properties were added to whey protein isolate gel (GWPI) to form MPNs-enhanced GWPI (GWPI@MPNs). This experiment first elucidated the mechanisms by which proanthocyanidins and calcium ions form MPNs and the molecular interactions between MPNs and WP. Then, the effects of adding different proportions of MPNs on the digestion kinetics and gel properties of GWPI@MPNs were determined. The indicators of digestion rate included degree of hydrolysis, digital image of the digestion process, SDS-page, and distribution of polypeptide molecular weight. Gel properties encompassed texture properties, rheological properties, denaturation behaviours, low-field nuclear magnetic resonance, and water-holding capacity. It was found that adding an appropriate amount of MPNs was an effective method to control the digestion rate and enhance the gel properties of GWPI. The mechanism might be that MPNs could enhance the intermolecular forces of WP and make the GWPI form a dense and uniform microstructure. The novel method developed in this research has the potential to contribute to overcoming the inherent limitations of WP and adding a new digestion related functional value for its application in the food industry.