| Naturally occurring phenolic compounds are pervasive in food plants. While some of these phenolic compounds are frequently added to processed foods as flavorings, others can be used as natural antioxidants. During thermal processing, the phenolic compounds undergo different thermal reactions and may have significant impacts on the sensory properties of processed foods.;I hypothesized that caffeic, ferulic, and chlorogenic acids, as hydrogen donors/radical scavengers, could affect formation of alkylpyrazine, pyridine, furan derivative, sulfur-containing heterocyclic compounds, and Strecker degradation products under roasting conditions. The objective of this study was to investigate effects of naturally occurring phenolic compounds on the formation of Maillard aromas and to explore the underlying mechanisms. The roast model systems of D-glucose with L-lysine, L-cysteine, or L-leucine were designed to study the effects, whereas caffeic, ferulic, and chlorogenic acids were selected as the naturally occurring phenolic compounds.;The results showed that catechol and 4-ethylcatechol were major degradation products of caffeic acid under coffee roast conditions. Study in the model systems of D-glucose with L-lysine or L-leucine indicated that naturally occurring phenolic compounds like caffeic, ferulic, and chlorogenic acids could inhibit alkylpyrazine formation under the roast conditions. Interestingly, these three phenolic compounds were also strong inhibitors for the formation of Strecker aldehydes from L-leucine. Their inhibitory capabilities followed in the order of ferulic acid > chlorogenic acid > caffeic acid.;Moreover, caffeic and chlorogenic acids suppressed the generation of polysulfur heterocyclic compounds, thiazoles, and thiophenes, in the L-cysteine/D-glucose roast systems. Specifically, the polysulfur heterocyclic compounds included 3,5-dimethyl-1,2,4-trithiolane and 5,6-dihydro-2,4,6-trimethyl-4H-1,3,5-dithiazine. The thiazoles contained thiazole, 2-methylthiazole, 4,5-dihydro-2-methylthiazole, 2-acetylthiazole, 5-ethyl-2-methylthiazole, and 2,4,5-trimethylthiazole, wheareas the thiophenes encompassed thiophene, 2-formyl-5-methylthiophene, and 2,3-dihydrothiophene.;In the L-leucine/D-glucose roast systems, caffeic, ferulic and chlorogenic acids were inhibitors for the formation of alkylfurans, including 2,5-dimethylfuran, 2,5-dihydrofuran, 2-propylfuran, tetramethylfuran, and 2-pentylfuran. While caffeic acid inhibited the formation of 2-ethylfuran, 2-furfural, and 5-methyl-2-furfural in the L-lysine/D-glucose systems, caffeic and chlorogenic acids suppressed the generation of 2,4-dimethylfuran, 2-ethylfuran, 2-acetylfuran, and 2-furanmethanol in the L-cysteine/D-glucose systems.;In addition, caffeic acid significantly inhibited the formation of 2-methylfuran, 3-hydroxy-2-acetylfuran, 2-furfural, 5-hydroxymethyl-2-furfural, and 5-methyl-2(3H)-furanone in the thermal degradation of D-glucose under the roast conditions. |
