Changes in whey protein produced by different sterilization processes and lactose content: Effects on glycosylation degree and whey protein structure

In this study, the interaction patterns between whey protein and lactose were investigated after different ratios of whey protein and lactose (1:2.5; 1:3.0; 1:3.5; 1:4.0; 1:4.5) were treated with two typical sterilization process parameters in powdered products (68°C, 20 min; 72°C, 15 min) and two typical sterilization process parameters in liquid products (121°C, 10 min and 121°C, 15 min). It was found that the degree of the Maillard reaction of whey protein-lactose solution increased with increasing lactose content, increasing sterilization temperature, or extending sterilization time, which was accompanied by changes in the protein structure of whey protein. In addition, glycosylation accelerates the decrease in free sulfhydryl content, decreasing surface hydrophobicity and decreasing fluorescence intensity. These findings highlight the advantages of designing protein-carbohydrate formulations with a high ratio of whey protein-lactose (1:2.5) to meet the requirements of the product standards for preterm/low-birth-weight infant formulas. When comparing only the sterilization processes of powder and liquid products, the pasteurization process of powder products significantly reduced the degree of the Maillard reaction caused by heat treatment and reduced protein denaturation.