| Abstract
| - Mechanisms of how epicatechin alters the pathways of the Maillard reaction were investigated. Carbon-13 and nitrogen-15 labeling studies were utilized to define the reactivity of epicatechin with glucose,glycine, and/or reaction products in an aqueous model (pH 7, 125 °C for 30 min) via GC, GC/MSand HPLC/MS analysis. Quantification of the volatile reaction product isotopomers by GC/MS froma 1:1 labeled to unlabeled glucose (carbohydrate module labeling technique) plus glycine model systemindicated the formation of 2,3-butanedione and acetol were primarily formed via intact C4 and C3sugar fragments, whereas pyrazine, methylpyrazine, 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine,and cyclotene were primarily formed via intact C2/C2, C2/C3, C3/C3, C3/C3, and C3/C3 sugar fragmentpairs, respectively. The formation of these seven compounds was also reported by GC analysis tobe dramatically inhibited when epicatechin was added to the glucose/glycine model system (observed9−113-fold reduction). HPLC/MS analysis of both the glucose-labeled and glycine-labeled modelsystems with and without epicatechin indicated that epicatechin reacted directly with C2, C3, and C4sugar fragments, while epicatechin did not report any direct reactivity with glycine. In conclusion, thequenching of sugar fragmentation products via epicatechin was correlated with the observed inhibitionon volatile compound formation when epicatechin was added to a glucose/glycine aqueous reactionmodel system. Keywords: Maillard reaction; nonenzymatic browning; inhibit; epicatechin; polyphenolic; sugarfragments; reactivity
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