The effect of B-type procyanidin on free radical and metal ion induced β-lactoglobulin glyco-oxidation via mass spectrometry and interaction analysis.

Procyanidin is a group of dietary flavonoids abundant in berry fruits. In this study, the effects and underlying mechanisms of B type procyanidin (PC) on free radical and metal ion (HO, AAPH and Fe) induced milk protein β-lactoglobulin (BLG) glyco-oxidation were investigated. The results indicated that PC protected BLG structure changes from cross-link and aggregation induced by free radicals and metal ion. Additionally, it effectively inhibited BLG oxidation by reducing approximately 21%-30% carbonyls and 15%-61% schiff base crosslink formation. Also, PC suppressed BLG glycation by inhibiting 48-70% advanced glycation end-products (AGEs) and reduced the accumulation of intermediate product methylglyoxal (MGO). The corresponding mechanisms were elucidated that PC exhibited great free radical scavenging and metal chelating properties; PC had non-covalent bind with the amino acid residues (preferably lysine and arginine) of BLG and blocked them from glycation; PC interrupted BLG glycation by forming procyanidin-MGO conjugates. Therefore, B type procyanidin was an effective glyco-oxidation inhibitor in milk products.