Effect of 2'-fucosyllactose and hydrolysis degree on oxidation, Maillard reaction, and physical stability of whey protein hydrolysate emulsions.

Processing of liquid infant formulas inevitably triggers undesirable side reactions affecting product quality and nutritional value. This study investigated the effects of whey protein hydrolysis (WPH) at different degrees of hydrolysis (DH; 0%, 6%, 8%, and 10%) and 2'-fucosyllactose (2'-FL) on the physical stability, protein oxidation, lipid oxidation, and Maillard reaction in infant formula model emulsions. Increasing DH progressively enhanced DPPH and ABTS radical scavenging activities, resulting in lower peroxide values and thiobarbituric acid reactive substances, thereby improving lipid oxidative stability. In contrast, higher DH intensified protein carbonyl formation and accelerated Maillard reaction progression, as enzymatic hydrolysis exposed abundant free amino groups and peptide fragments susceptible to oxidative modification and glycation. Partial replacement of lactose with 2'-FL effectively mitigated protein oxidation, inhibited lipid oxidation, and retarded the formation of advanced glycation end products. These effects may be attributed to its inherent antioxidant capacity and interactions with whey peptides further strengthen antioxidant activity. However, 2'-FL adversely affects emulsion physical stability, increasing droplet size and Turbiscan Stability Index. Correlation analysis further confirmed the complex interrelationships among physical stability, lipid oxidation, protein oxidation, and Maillard glycation in the emulsion system. These findings highlight the dual regulatory effects of hydrolysis and 2'-FL in emulsion systems, providing insights for optimizing liquid infant formulas to reduce heat-induced adverse reactions while maintaining quality.