Effect of glycation derived from α-dicarbonyl compounds on the in vitro digestibility of β-casein and β-lactoglobulin: A model study with glyoxal, methylglyoxal and butanedione

alpha-Dicarbonyl compounds, which are widely found in common consumed food, are one of the precursors of advanced glycation end products (AGEs). In this study, the effect of glycation derived from glyoxal (GO), methylglyoxal (MGO) or butanedione (BU) on the in vitro digestibility of beta-casein (beta-CN) and beta-lactoglobulin (beta-Lg) was investigated. Glycation from alpha-dicarbonyl compounds reduced the in vitro digestibility of studied proteins in both gastric and intestinal stage. In addition, glycation substantially altered the peptides released through gastric and gastrointestinal digestion, as detected by liquid chromatography electrospray-ionization tandem mass spectrometry (LC-ESI-MS/MS). Crosslinked glycation structures derived from BU considerably reduced the sensitivity of glycated beta-Lg towards digestive proteases, albeit to a lesser degree in glycated beta-CN due to its intrinsic unordered structure. By contrast, non-crosslinked AGEs that formed adjacent to enzymatic cleavage sites did not block the enzymatic reaction in several cases, as evidenced by the corresponding digested peptides modified with glycation structures. These findings expand our understanding of the nutritional influence of alpha-dicarbonyl compounds and health impact of relevant dietary AGEs.