Effects of Liquid Fermentation by Aspergillus on Volatile Components of Sun-dried Green Tea Infusion Based on HS-SPME-GC-MS Combined with Chemometrics
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Abstract:
The effects of liquid fermentation by Aspergillus on the aroma characteristics and volatile components of sun-dried green tea infusion were investigated through sensory evaluation, headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and chemometrics. The results show that unfermented sundried green tea infusion exhibits fresh and nectar aromas, while fermentation with Aspergillus niger alone results in a fatty aroma. In contrast, fermentation with Aspergillus oryzae alone produces floral and fruity aromas along with a mint aroma. Moreover, the infusion subjected to mixed fermentation exhibits a woody aroma with a slight fatty note. Fermentation with Aspergillus oryzae retains the highest alcohol content (13.76%), significantly increases the ester content (24.76%), and produces the greatest number of total and characteristic volatile components (23), including methyl salicylate (mint aroma) and benzyl salicylate (fruity aroma). Fermentation with Aspergillus niger retains the highest aldehyde content (4.44%) and significantly enhances ester content (20.14%). Mixed fermentation significantly increases the content of ketones (9.09%) and hydrocarbons (18.94%). Principal component analysis and Euclidean distance clustering reveal that the volatile components of the tea infusion fermented by Aspergillus oryzae alone are the most distinctive. Overall, fermentation using single strains and mixed strains significantly alters the aroma characteristics of sun-dried green tea infusion. Specifically, Aspergillus oryzae is identified as a superior aroma-producing strain in liquid fermentation, exhibiting a synergistic effect with Aspergillus niger to enhance the flavor of tea infusion. These results provide a theoretical basis for aroma enhancement technology and the development of diversified fermented tea products, which support innovation in the tea industry.
