Quality Characteristics and Metabolomics Analysis of Two New Varieties of <i>Tremella fuciformis</i>

<i>Tremella fuciformis</i> Berk., also known as white fungus and snow fungus, is one of the important edible and medicinal mushrooms in China. The quality characteristics and metabolites of different <i>T. fuciformis</i> varieties directly affect the stability of their processed products. In this study, two new varieties of <i>Tremella fuciformis</i>, namely ’TYH-SD1’ (yellow) and ’TWH-SD2’ (white), which were obtained by the team through single-spore crossbreeding and its control varieties Tr21 (yellow) and Tr01 (white), were used as test materials. The characteristics and nutritional quality of the four varieties of substrates were comparatively analyzed, while metabolomics was employed to investigate the differences in flavor substances. The results demonstrate that TYH-SD1 and TWH-SD2 had a higher rehydration rate and faster rehydration speed compared with the control strains Tr21 and Tr01, with a smaller stem and higher yield. Notably, TWH-SD2 had a 29.06% increase in its rehydration rate and it had higher contents of crude polysaccharide and vitamin D₃. The surface of TYH-SD1 ear pieces exhibited a porous structure with a larger pore size and the surface of TWH-SD2 ear pieces displayed a surface characterized by connected gully-like protrusions and fewer indentations, which were significantly different from that of Tr21 and Tr01 ear pieces. The textural analysis shows that TYH-SD1 and TWH-SD2 ear pieces were softer and more elastic, with greater cohesion and recovery, indicating that they had high tensile and deformation recovery ability. Metabolomics analysis revealed that the relative content of aldehydes in the volatile flavor substances TYH-SD1 and TWH-SD2 was high in n-alpha-aldehyde, nonanaldehyde, and n-pentanal. The relative content of alkanes in TYH-SD1 was second only to that of aldehydes, with decane having the highest content, contributing to its more almond aroma, fruity aroma, and fat aroma. TWH-SD2 exhibited the highest concentration of alcohols, accounting for 43.57%, which may result in a clear, mushroom, and lipid odor. The above results will provide theoretical basis for the further production, processing, and application of the new varieties.