Structure-dependent effects of flavan-3-ols on 3-aminopropionamide deamination and acrylamide formation in the Maillard reaction.
Although flavan-3-ols are extensively utilized as acrylamide inhibitors in thermal food processing, their variable efficacies suggest a more complex, unresolved mechanism. Overcoming the traditional perspective of simple inhibition, this study reveals a paradoxical, structure-dependent dual effect of four typical flavan-3-ols (EGCG, EGC, ECG, and EC) on acrylamide formation. While the net inhibitory efficacy in an asparagine-glucose system followed EGCG > EGC ≈ ECG > EC, investigations using a 3-aminopropionamide (3-APA) intermediate model demonstrated that the oxidation of the flavan-3-ol B-ring generated highly reactive quinone intermediates that actively facilitated acrylamide formation. This promotional capacity (EC > ECG > EGC > EGCG) inversely mirrored the net inhibitory trend. Crucially, UHPLC-MS/MS analysis tentatively identified nine novel quinone-amine adducts, providing structural evidence for this B-ring-mediated promotion. Consequently, the net impact of flavan-3-ols on acrylamide formation is not a simple linear inhibition, but a dynamic competition between A-ring-mediated carbonyl trapping and B-ring-mediated quinone generation. EGCG exhibits the most potent net inhibition because its highly substituted structure is exceptionally susceptible to competing side reactions, such as autoxidation and ester hydrolysis, which effectively quench the B-ring-driven promotion. These findings provide direct mechanistic and practical guidance for selecting galloylated tea polyphenols to mitigate acrylamide risk in thermally processed starchy foods.