Influence of the pH on the formation of pyrazine compounds by the Maillard reaction of L-ascorbic acid with acidic, basic and neutral amino acids

The influence of different pHs, ranging from 5.0 to 9.0, on the formation of pyrazines in the Maillard reaction of L-ascorbic acid with acidic, basic and neutral amino acids was studied. The results clearly showed that pyrazine formation was favored at higher pH. These findings suggest that the formation of pyrazines is catalyzed by base. However, pH affects the formation of pyrazines at different degrees for neutral, acidic and basic amino acids. The pH has the greatest impact on acidic amino acids and the least impact on basic amino acids and the impact of pH on neutral amino acids is in between. L-Cysteine behaves similar to acidic amino acids because of its weakly acidic mercapto group. Another finding is that the formation of some pyrazines is independent of the amino acid structure, and the amino acids are solely a nitrogen source and do not provide carbon skeletons. (C) 2011 Curtin University of Technology and John Wiley & Sons, Ltd.