Effect of pH on the volatile formation from the reaction between cysteine and 2, 5-Dimethyl-4-Hydroxy-3(2H)-furanone

The effect of pH on the volatile components formed by the reaction between cysteine and 2, 5-dimethyl-4-hydroxy-3(2H)-furanone was studied in a Parr bomb model system. pH values of 2.2, 5.1, and 7.1 represented points below, around, and above the isoelectric points of cysteine. At pH 2.2, the major components formed were 3-methyl-2-(2-oxopropyl)thiophene, 1, 2, 3-trithia-5-cycloheptene, 2, 5-dimethyl-4-hydroxy-3(2H)-thiophenone, and 2, 4-hexanedione. At pH 5.1, the major components formed were 3, 5-dimethyl-1, 2, 4-trithiolane isomers and 2, 5-dimethyl-4-hydroxy-3(2H)-thiophenone. At pH 7.1, various classes of heterocyclic compounds, including thiazoles, thiazolines, and pyrazines, were identified. All three of the reactions produced roasted and meaty aromas, but the reaction at pH 2.2 generated the best meat flavor in terms of the roasted and meaty notes evaluated.