Effects of two enzyme extracts of Aspergillus niger on green tea aromas

Green tea was investigated in terms of its aroma changes induced by two enzyme extracts of Aspergillus niger, i.e., crude enzyme extracted from fermentation using tea stalk medium (CETSM) and crude enzyme yielded in potato dextrose medium. The result showed that the former had significant effects on sensory indexes and volatile constituents, with significant increases in toasty and mushroom notes, while the latter had little influence on the aforementioned indexes. In addition, the volatile constituents were significantly affected; in particular, the contents of cis-3-hexenol, 1-octen-3-ol, eucalyptol, hexanol, and benzaldehyde increased. Furthermore, gas chromatography-olfactometry (GC-O) analysis showed that an increase in 1-octen-3-ol strengthened the mushroom note. These results indicate that CETSM contains some novel enzymes that can modify the aroma profile of green tea. This study also provides valuable information and suggestions to use fermented enzymes to modify food aromas.