Influence of the Maillard reaction on the structure of β-casein using a simulated cooking system

Abstract Glycation during food processing can change the structural 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 a simulated cooking system at 98 and 115 °C was investigated. The changes in ultraviolet absorption, endogenous fluorescence intensity, surface hydrophobicity, particle size, free amino group, free sulphydryl 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 hr (OH-MC-Glu). Results showed that glycation activities of five sugars were glucose > sucrose > soluble starch> amylopectin ≈ amylose. Under the simulated cooking system, the secondary structure and conformation of glycated MC changed to different degrees, which were affected by the glycation degree. Moderate glycation (0–2 hr of heating) may promote the conversion reaction of sulfhydryl-disulfide bond (SH-SS) in MC, causing cross-linking and self-aggregation of MC, and induce the particle size increase of MC. Excessive glycation (2–6 hr of heating) can further reduce the surface hydrophobicity of MC, inhibit self-aggregation of MC, and reduce the particle size of MC.