The influence on the structure and allergenicity of milk β-lactoglobulin by methylglyoxal during thermal processing

This study aims to investigate the effects of the typical glycation intermediate methylglyoxal (MGO) on the structure and allergenicity of milk β-lactoglobulin (βLG) during thermal processing. Structural changes were assessed using SDS-PAGE, intrinsic fluorescence, circular dichroism, and HPLC-MS/MS. Allergenicity was evaluated through in vitro and in vivo experiments. The conformational changes of βLG significantly were induced by MGO during heat treatment, with a 41.3% decrease in α-helix content and a 25.4% increase in random structure. Furthermore, the lysine, arginine, aspartic acid, and histidine residues in βLG were modified by MGO, which may disrupt or mask allergenic epitopes. Additionally, MGO treatment resulted in a reduction of 41.1% and 26.8% in the pro-inflammatory mediators histamine and β-hexosaminidase in KU812 cells, respectively. Additionally, cytokine levels of IL-4 and IL-13 were reduced by 26.3% and 21.75%, respectively. In mouse experiments, compared to the βLG group, the MGO-βLG group showed a 2-4 fold decrease in IgE, IgG, and IgG1 levels. After reacting with βLG, MGO can reduce serum histamine release by up to 73.9% and mast cell protease-1 (MCP-1) release by 40.8%. These results indicate that the typical glycation intermediate MGO can modify the allergenic epitopes of milk βLG during thermal processing, thereby affecting its allergenicity. This study provides a reference for elucidating the natural rules of allergenicity changes during milk thermal processing.