Volatile Compounds Produced by the Reaction of Leucine and Valine with Glucose in Propylene Glycol

Equimolecular amounts of amino acids (l-leucine and l-valine) and d-glucose were refluxed at 140 °C for 2 h in propylene glycol. The volatiles were isolated by simultaneous steam distillation and extraction. The extracts were separated in advance by column chromatography on silica gel with a benzene−ether gradient. The resulting fractions were analyzed by GC and GC-MS. Twenty-seven compounds, including 13 pyrazines, 6 dioxolanes, 2 aldehydes, 2 acids, and 2 pyridines, were identified. Dioxolanes, aldehydes, and pyrazines are the major volatiles, and the percentages of their total gas chromatographic peak areas are 41.13, 23.67, and 17.69 respectively. Formation pathways and sensory properties are described. Keywords: Volatile compounds; Maillard reaction; model reaction system