Differential Volatiles and Sensory Quality of Green Tea- and Black Tea-infused Rice Wines

Objective Effects of rice wine fermented with green tea or black tea on the sensory quality, microbial community, and functional activities of the resulting products were studied.

Method Rice wines were brewed with green tea (W-GT) or black tea (W-BT) made from a same batch of fresh leaves, as well as control (W-C) without the tea addition but an equal volume of distilled water. On the prepared wines, sensory evaluation was conducted by an expert panel, microbe structures analyzed by 16S rRNA and ITS high-throughput sequencings, and functional activities predicted using PICRUSt2. The headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was employed to identify characteristic flavor components with relative odor activity value (rOAV) determined. Correlation between the microbes and metabolites was used to unveil microbial roles in the wine flavor formation.

Result The sensory panel indicated that the yellowish-green W-GT had a refreshing taste with a delicate, elegant green-tea aroma, while the bright orange-yellow W-BT exhibited a mellow flavor with a pronounced honey-like aroma and full-bodied mouthfeel. W-BT was abundant on the functional genes, particularly those in the metabolic pathways, whereas W-GT was highly enriched in the functional genes related to genetic information processing and drug resistance. Based on 16S rRNA, Firmicutes was the dominant phylum in W-GT, and Leuconostoc the prevailing genus in both W-BT and W-GT. The ITS sequencing showed that Mucoromycota dominated at the phylum level among all, Saccharomyces and Mucor abundant at the genus level in W-BT, and W-GT rich in fungal diversity. A total of 922 volatiles, mainly esters, terpenoids, and ketones, were identified by GC-MS. The top 10 characteristic components scored on rOAV were β-ionone, 3-methylpentanal, (Z,Z)-3,6-nonadienal, (E,Z)-2,6-nonadienal, 8-nonenal, (E)-2-hexenal, (E,E)-3,5-octadien-2-one, 1-Nonen-3-one, (E)-β-ionone, and trans, cis-2,6-nonadien-1-ol. Among them, β-ionone was significantly higher on the values ranging from 18,173.75 to 22,879.45. On differential metabolites, W-GT was significantly upregulated on terpenoids, while W-BT enriched on phenols and aldehydes. The correlations between the core microbiota of Mycobacterium in W-GT and Blautia in W-BT were involved in the formation of the characteristic flavor compounds in the two tea-infused rice wines.

Conclusion From the perspective of tea–microbe–wine interactions, the cause of quality differentiations of W-GT and W-BT seemed apparent. The microbes from the added green tea regulated the metabolic activity that enriched the terpenoid formation in W-GT; whereas the polyphenols from the fermented black tea and the aldehydes formed from the aroma-producing probiotics augmented the opulent flavor in W-BT.