Investigation of the change in the flavor of a coffee drink during heat processing.

Heat processing is responsible for the change in the flavor of a coffee drink. In this study, the application of gas chromatography-olfactometry of headspace samples (GCO-H) using the vapor fraction before and after heat processing of the coffee samples resulted in the detection of 12 odor-active peaks for which the flavor dilution (FD) factors changed. Eight potent odorants were identified from these peaks by gas chromatography-mass spectrometry (GC-MS). Among these components, methanethiol (putrid), acetic acid (sour), 3-methylbutanoic acid (sour), 2-furfuryl methyl disulfide (meaty), and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like) increased after heating of the coffee sample, whereas 2-furfurylthiol (roasty), methional (potato-like), and 3-mercapto-3-methylbutyl formate (roasty) decreased compared with the coffee sample before heat treatment. In addition, extensive studies have been carried out on the pH effects on the change in the concentration of 2-furfurylthiol during heat processing and in the pH range of 5-7; it was found that the concentration of this compound in the model solutions had significantly changed.