EFFECT OF PH ON PYRAZINE FORMATION IN GLUCOSE GLYCINE MODEL SYSTEMS

Pyrazines produced from a D-glucose/L-glycine model browning system at eight pH values ranging from one to 12 were isolated by extraction and identified by combined gas chromatography/mass spectrometry. Thirty-two compounds were identified in this study including: 19 pyrazines, nine other nitrogen-containing (non-pyrazine) products, and four oxygenated products. As the pH increased, the number of pyrazines produced also increased. The greatest varieties of pyrazines were produced at pH 9.00 and 9.64 in which all 19 pyrazines detected in this study were formed at trace or greater quantities. The major pyrazines generated were 2,3,5-trimethylpyrazine, 2,5-dimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, 2,3,5,6-tetramethylpyrazine and 2,3-diethylpyrazine.