Formation pathways of 3-hydroxy-4,5-dimethyl-2[5H]-furanone (sotolon) in citrus soft drinks

After storage of citrus soft drinks supplemented with a vitamin mixture an off-flavor described with 'burnt' and 'spicy' was detected. Gas chromatography-olfactometry (GCO) and gas chromatography-mass spectrometry (HRGC-MS) revealed 3-hydroxy-4,5-dimethyl-2[5H]-furanone (sotolon) as the off-flavor formed during storage. Among the ingredients of the soft drinks, ethanol and ascorbic acid were found to be the essential precursors of sotolon. Two formation pathways were postulated on the basis of studies using ²H-(D) and ¹³C-labeled ethanol and ascorbic acid. Sotolon is either formed from two molecules of ethanol and carbons 2 and 3 of ascorbic acid (pathway 1) or it is generated from one molecule of ethanol and carbons 3, 4, 5 and 6 of ascorbic acid (pathway 2).