Biosynthesis of pleasant aroma by enokitake (Flammulina velutipes) with a potential use in a novel tea drink

Western consumers prefer tea products with little or no green flavor. Accordingly, edible basidiomycetes have been addressed as an innovative tool to naturally aromatize tea infusion to mask or reduce green flavor. After submerged fermentation of green tea infusion with basidiomycetes, multiple pleasant odor impressions were perceived which significantly differed from the characteristic green and floral odor of the substrate. Among twenty-nine screened fungi, enokitake (Flammulina velutipes) was regarded as an ideal species to potentially drive a sensorial tea drink because of its appealing nutty and chocolate-like flavor and a rapid fermentation process (16 h). To better understand flavor formation during fermentation as perceived by sensory evaluation, the flavor profile was decoded by direct immersion – stir bar sorptive extraction – gas chromatography – mass spectrometry – olfactometry. During the fermentation, a series of key odorants of the non-fermented tea infusion imparting green and floral were decreased, while compounds responsible for the nutty and chocolate-like aroma increased. Enokitake biosynthesized the sensory-relevant compound 2-ethyl-3,5-dimethylpyrazine, which has not been reported in basidiomycetes yet. We assume that vitamin B1 and sodium acetate are potential precursors in enokitake. In parallel, the accumulation of various alkylpyrazines (2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, and 2-ethyl-3,6-dimethylpyrazine) has been observed as well.