Investigation of the reaction between 4-hydroxy-5-methyl-3(2H)-furanone and cysteine or hydrogen sulfide at pH 4.5.

Reaction of 4-hydroxy-5-methyl-3(2H)-furanone (HMF) with cysteine or hydrogen sulfide at pH 4.5 for 60 min at 140 degrees C produced complex mixtures of volatile compounds, the majority of which contained sulfur. Sixty-nine compounds were identified, some tentatively, by GC/MS. These included disulfides (26), thiols (7), dithiolanones (6), thiophenones (4), dithianones (3), and thienothiophenes (6). The main non-sulfur compounds were 2, 3-pentanedione, 2,4-pentanedione, and 3,4-hexanedione. Both systems produced approximately the same total quantity of volatile compounds, but the reaction containing cysteine gave the larger number of individual compounds, with thiols quantitatively the dominant components. By comparison, the major products formed in the reaction with hydrogen sulfide were the dithiolanones. Reaction pathways are presented for the major products and, where applicable, possible reasons for the differences in composition of the two systems are discussed. The contribution of these reactions, and their products, to the flavor of roasted foods is considered.