Inhibitory effects of polyphenols on the Maillard reaction in low-lactose milk and the underlying mechanism

In this study, low-lactose milk (LLM) was heat-treated under different conditions and stored at 4°C, 25°C, and 37°C for 15 d, after which the changes in the Maillard reaction (MR) of LLM were investigated. The contents of α-dicarbonyl compounds and 5-hydroxymethylfurfural (5-HMF) in LLM after the addition of polyphenols were determined via HPLC, and the inhibitory effects of 3 different concentrations of epigallocatechin gallate (EGCG), dihydromyricetin (DMY), and procyanidin (PC) on the MR of LLM were studied. The fluorescence intensity of LLM was measured at 290, 300 and 310 K, the fluorescence quenching types and binding constants of PC on CN were investigated, and thermodynamic analysis was carried out. These results suggest that the optimal heat treatment conditions were 80°C for 15 s and that the optimal storage conditions were 4°C. In the α-dicarbonyl compound capture and 5-HMF inhibition tests, PC had the greatest inhibitory effect at a concentration of 0.2 mg/mL, with an inhibition rate of 48.19%. Therefore, PC is more stable than the other 2 polyphenols. The mechanism of inhibition involves the formation of matrix complexes between PC and CN in LLM, resulting in static quenching of the LLM and thus a reduction of the inhibitory effect. The thermodynamic analysis revealed that the binding of PC to CN was an exothermic reaction, and the combination of the 2 was driven mainly by hydrogen bonding and van der Waals forces. This study lays a theoretical foundation for the development of LLM.