Xiaofen Wu,Tetsuo Ozawa,Yinhua Li,Jihua Duan,Kun Zhu,Jianan Huang,Zhonghua Liu,Keqin Wang
This study evaluated the effects of fermentation time and temperature on the content of high molecular weight polyphenol mitochondrial activation factors (MAFs) and other polyphenols in Congou black tea using high-performance liquid chromatography (HPLC). There were two broad chromatographic peaks in the HPLC spectra of MAFs: MAFs-1 (16.163 min) and MAFs-2 (34.31 min); MAFs-2 was satisfactorily analyzed by HPLC, with separation by paper chromatography. The MAFs-2 contents increased gradually in different varieties of Congou black tea as the fermentation time and temperature increased; the maximum MAFs-2 content was 5.11% in Xiaoxianghong 21-3 after 8 hr of fermentation. The total polyphenols and catechins contents decreased, whereas the theabrownins contents increased as the fermentation time and temperature increased; the theaflavins and thearubigins contents in different Congou black teas showed different variation tendencies. Therefore, studies regarding changes in polyphenols during fermentation will help improve the quality of Congou black tea and enhance its health benefits. Novelty impact statement A new method for the determination of MAFs-2 by high-performance liquid chromatography combined with paper chromatography was established. The content of MAFs-2 increased initially and then stabilized as fermentation was continued from 2 to 8 hr, it increased gradually as the fermentation temperature was increased from 23 to 37°C. These results provide a new analytical method for MAFs in black tea and a theoretical basis and technical guidance for improving the quality of Congou black tea.
This study focused on the efficiency of enzymatic synthesis for theaflavins (TFs) and SII types of thearubigins (SII-TRs) in suspended fermentation of different varieties of tea leaves. The results showed that the content of catechins in tea variety-Xiaoxianghong 21-3 (XXH21-3) was the highest among the five kinds of fresh tea leaves, and it had the strongest ability of transforming catechins to TFs and SII-TRs. The total amount of catechins for XXH 21-3 decreased rapidly and the conversion ratio of TFs reached the highest level of 13.96% after 20 min, the residual catechins was the lowest (3.08%) and the conversion rate of SII-TRs was the highest (13.02%) after 120 min during the suspended fermentation of five varieties tea leaves. Among the six catechin types, epicatechin gallate (ECG), epigallocatechin gallate (EGCG) and epigallocatechin (EGC) were consumed in large quantities, and the residues were all less than 5% in the final stage of fermentation, of which ECG consumption was the fastest, followed by EGCG. These results demonstrated that the concentration of catechins and PPO activities were positively correlated with the formation of TFs and SII-TRs, POD activity was positive correlation with synthesis of SII-TRs and negative correlation with TFs.
Aspergillus cristatus , the predominant microbe of Fuzhuan brick tea (FBT) , is responsible for the creation of distinctive golden flower and unique floral aroma of FBT. The present study examined the alterations in chemical and aromatic components of raw dark tea by solid-state fermentation using A. cristatus (MK346334), the strain isolated from FBT. As results, catechins, total ployphenols, total flavonoids, theaflavins, thearubigins and antioxidant activity were significantly reduced after fermentation. Moreover, 112 and 76 volatile substances were identified by HS-SPME-GC–MS and HS-GC-IMS, respectively, primarily composed of alcohols, ketones, esters and aldehydes. Furthermore, the calculation of odor activity values revealed that 19 volatile chemicals, including hexanal, heptanal, linalool and methyl salicylate, were the main contributors to the floral, fungal, woody and minty aroma of dark tea. The present research highlights the pivotal role played by the fermentation with A. cristatus in the chemical composition, antioxidant property and distinctive flavor of dark tea.
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