Influence of Maillard reaction on structure of β-casein during simulated cooking system

Abstract Glycation during food processing can change structure characteristics of dietary protein and endow a variety of functionalities. Milk β-casein (MC) with five different types of carbohydrates (i.e., glucose, sucrose, amylose, amylopectin, and soluble starch) in simulated cooking system at 98 °C and 115 °C were investigated. The changes in ultraviolet (UV) absorption, endogenous fluorescence intensity, surface hydrophobicity, particle size, free amino group, free sulfhydryl group, and circular dichroism were measured. For the glucose-added group, the lowest free amino content and most significant spectral changes among all groups were observed after heating at 115 °C for 6 h (OH-MC-Glu). Results showed that glycation activities of five sugars were: glucose > sucrose > soluble starch> amylopectin ≈ amylose. Under simulated cooking system, the secondary structure and conformation of glycated MC changed to different degrees, which were affected by the glycation degree. Moderate glycation (0 to 2 h of heating) may promote the conversion reaction of SH-SS in MC, causing cross-linking and self-aggregation of MC, and induce the particle size increasing of MC. Excessive glycation (2 h to 6 h of heating) can further reduce surface hydrophobicity of MC, inhibit self-aggregation of MC, and reduce particle size of MC.