Effect of Fermentation by Eurotium cristatum LJSC.2001 on the Fermentation Quality of Raw Dark Tea Made from Different Varieties

The current study was performedin order to explore the effect of Eurotium cristatum LJSC.2001 on the fermentation quality of raw dark tea. Golden flower loose tea was produced by using E. cristatum LJSC.2001 to ferment raw dark tea from the cultivars Zhuyeqi, Yuntaidaye and Taoyuandaye provided by representative manufacturers (Yuntaishan, Yunshang, Baishaxi and Junhe) in Anhua, Hunan province, and comparative analysis of their taste and aroma quality was carried out by sensory evaluation, basic physicochemical analysis, analysis of catechin components by high performance liquid chromatography (HPLC), and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Results showed that after fermentation by E. cristatum LJSC.2001, the dry tea samples were darker in colorand fully covered with golden flower; their infusions were darker in color, and had a strong fungal aroma and a mellow and full taste, and the brewed tea was soft. Raw dark tea from Baishaxi had a stronger fungal aroma after fermentation, while retaining a distinct pine smoke-like aroma. The contents of taste compounds including tea polyphenols, free amino acids, soluble carbohydrates, flavonoids, total catechins, myricetin, quercetin, and kaempferol showed an overall decreasing trend. The content of catechins in Yuntaidaye raw dark tea from Yuntaishan and Yunshang declined most. The relative contents of esters and aldehydes increased after fermentation. There were differences in the content of volatile components among the different fermented tea samples, methyl salicylate and (E,E)-2,4-heptadienal being the major ones. Multivariate statistical analysis showed significant differences in volatile composition between golden flower loose tea and raw black tea. There were 19 characteristic volatile components identified including methyl salicylate, (E,E)-2,4-heptadienal, (E)-linalool 3,7-oxide, (E)-furan oxidized linaloa, acetophenone, (E)-2-, (Z)-6-nonadienal, (E)-2-hexenal, (E,E)-3,5-octadien-2-one and n-tridecane. The contents of the nine volatile components increased significantly after fermentation, and they all contributed to the fungal aroma of golden flower loose tea. It can be seen that fermentation by E. cristatum LJSC.2001 can impart a more mellow and fuller taste and a more prominent fungal aroma to raw black tea.