Screening of Floral Flavor-producing Clavispora lusitaniae and Its Effect on Coffee Quality

Fermentation was a key factor impacting coffee quality. However, coffee-fermenting microbial strains that produce floral flavors were scarce. A floral flavor-producing yeast strain was selected from Jiuqu samples. This strain was identified by morphological test, physiological and biochemical analyses, and 18S rDNA sequencing, and then applied to coffee bean fermentation under the conditions of 48 h duration, 30 ℃ temperature, and 0.1% (v/m) inoculum size. Gas chromatography-mass spectrometry combined with flavor component analysis, volatile components difference, odor activity value (OAV) and sensory evaluation were used to explore the influence of fermentation on coffee quality. A floral flavor-producing strain was obtained and identified as Clavispora lusitaniae CAU417. Compared with those in the control group, reductions of 54.0% and 33.3% were observed in the caffeine and trigonelline contents, respectively, in the fermented coffee powder, leading to a substantial reduction in the coffee's bitter taste (P<0.05). Sixty-two volatile compounds were identified in the fermented coffee, of which the contents of furans and pyrazines were the highest, accounting for 38.8% and 17.5% of the total volatile compound content, respectively. Compared with those in the control group, the OAV value of phenylethanol and 3-furfural in the fermented coffee increased by 920% and 24.3%, respectively. Coffee beans fermented by Clavispora lusitaniae CAU417 exhibited a prominent rose aroma, along with caramel, honey, cream, chocolate, nut, toasted, and fruity aromas. Correlation analysis revealed that the floral flavor was significantly positively correlated with phenylethanol (P<0.05), while the bitter and astringent taste exhibited significant negative correlations with chlorogenic acid, caffeine, and trigonelline (P<0.05). Thus, Clavispora lusitaniae can be used as an excellent coffee bean starter, which provide a theoretical basis and technical support for improving coffee quality.