Digestibility of polymerized whey protein using in vitro digestion model and antioxidative property of its hydrolysate

Polymerized whey protein (PWP) is whey protein aggregates formed by heating whey protein at certain conditions. PWP has been successfully used as thickening agent, fat replacer and microcapsule wall material. However, the digestion properties of PWP have not been systematically investigated. This study aims to analyze zeta potential, particle size, peptide composition, and antioxidative property of digested PWP (prepared by heating at 70-85 degrees C for 10-30 min) obtained by hydrolyzing with pepsin and trypsin sequentially using in vitro digestion model. Digestive products of PWP heated at 85 degrees C showed more significantly negative zeta potential in comparison with that of control sample (p < 0.05). Heating temperature up to 80 degrees C and 85 degrees C resulted in significantly boarder size distribution and lower particle size of digestive products of PWP than other samples (p < 0.05). Compared with control sample, PWP samples released more peptides after digestion and the increased number depended on heating temperature and time. Heating increased the sequence coverage of the main whey proteins by generating some new peptides. Compared with control sample, digested PWP showed improved 2,2'-azinobis(2-ethylbenzothiazoline-6-sulfonate) (ABTS) scavenging ability. Data indicated that digestion property of whey protein can be changed by manipulating protein conformation with heat treatment before digestion.