Abstract:Semi-dry dehulled coffee beans were treated with different Saccharomyces cerevisiae CMCC1793, CMCC1425, CMCC1557, CMCC32762 strains to ascertain differences in the volatile compounds under exposure. Beans were dried, shelled, and medium-roasted to obtain six samples: GK, HK, JK, ZK, MK, and CK, which were then subjected to headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS), odor activity value (OAV), and sensory evaluation, after which the physical and chemical characteristics were used to evaluate the samples. The results showed different volatile compounds for roasted beans inoculated with different S. cerevisiae strains, and of the 81 volatile compounds identified, 49, 52, 50, 52, 58, and 46 volatile compounds were identified in CK, GK, HK, JK, MK, and ZK with contents of 301.03, 286.31, 223.15, 333.05, 262.22, and 372.51 μg/g, respectively. Pyrazine compound content was highest in JK at 122.99 μg/g, with ketone compounds the second highest at 53.02 μg/g. OAV analysis indicated the presence of 12 compounds with OAV values not less than one, of which 3-ethyl-2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2-acetylpyrrole and 2,5-dimethyl pyrazine showed the highest values in JK. These compounds contribute greatly to the coffee aroma system. Sensory evaluation showed that coffee samples inoculated with S. cerevisiae generally had higher scores than the uninoculated samples, and the scores for aftertaste and balance were higher in JK than the other coffee samples. In conclusion, CMCC 1557 is the most suitable microbial starter for the semi-dry processing of coffee. This study provides a theoretical basis and technical support for upgrading and improving the primary processing and flavor quality of coffee.
