The interfacial covalent bonding of whey protein hydrolysate and pectin under high temperature sterilization: Effect on emulsion stability

In this study, the effect of high-pressure steam sterilization (121 °C for 15 min) on whey protein hydrolysate-pectin solutions and emulsions was studied. The interaction and emulsification characteristics of pectin and whey protein concentrate (WPC) were evaluated from the solution system to the emulsion system. Enzymatic hydrolysis of WPC (WPH, 2 % and 8 % degree of hydrolysis) increased the covalent binding with pectin, which reduced the heat-induced aggregation of protein and improved emulsification. The thermodynamic incompatibility between WPC and pectin was not conducive to the covalent bonding under high temperature sterilization and produced serious aggregates, which also made a rapid increase in particle size (up to ∼3 μm), compared to WPH-pectin emulsion (∼ 400 nm). In addition, if emulsion was stirred during the sterilization, the creaming and protein aggregation could be avoided. By comparing low methoxy pectin (LMP) and high methoxy pectin (HMP), it was found that the whey protein-HMP complex had better emulsification stability, and the steric stabilization played a more important role in emulsion stability than the electrostatic repulsion. The changes of whey protein and pectin at the oil-water interface of the emulsion during the sterilization process may provide a reference for the sterilized bioactive ingredient delivery system.