Repeated thermal treatment could impair the flavor of instant black tea(IBT)as the volatile compounds and characteristic constituents dramatically vary during the manufacturing process.Utilization of fresh leaves as r...Repeated thermal treatment could impair the flavor of instant black tea(IBT)as the volatile compounds and characteristic constituents dramatically vary during the manufacturing process.Utilization of fresh leaves as raw material in IBT manufacture at low temperature may become an alternative to conventional extraction methods.This study aimed to improve the quality of IBT using fresh tea leaves by a two-stage enzymatic processing.The influence of combined enzymatic oxidation and extraction conditions for maximal extractable flavour(taste and aroma)characteristics from fresh tea leaves were investigated.The changes of aroma profiles and chemical constituents including theaflavins(TFs),thearubigins(TRs),theabrownines(TBs)and TRs/TFs ratio in converted tea brews under two-stage enzyme catalyzed fermentation and extraction conditions were further compared between different treatments,based on which the optimised conditions were determined.During the two-stage enzymatic processing,75 kinds of volatile compounds were identified in all processed samples,and the contents of TFs,TRs,TBs and TRs/TFs ratio could be optimized by adjusting different procedures and parameters.The overall properties of final product were compared with two types of commercial IBT.High quality IBT with desired properties and antioxidant activity can be manufactured using fresh tea leaves by two-stage enzymatic processing approach.展开更多
Aroma is one of the most important factors for the flavor, taste, and quality of pu-erh tea, and the post-fermentation process has an important influence on the aroma of pu-erh tea. In the present study, the influence...Aroma is one of the most important factors for the flavor, taste, and quality of pu-erh tea, and the post-fermentation process has an important influence on the aroma of pu-erh tea. In the present study, the influence of fungi fermentation on the flavor of pu-erh tea was investigated and compared. Volatile compounds from pu-erh tea fermented by four Aspergillus strains, including A. niger, A. oryzae, /1. awamori, and A. glaueus, were extracted and analyzed using ultrasound-assisted extraction-dispersive liquid-liquid microextraction-gas chromatography-mass spectrometry （UAE-DLLME-GC-MS）, and a total of 63 volatile compounds were identified. In comparison with the sun-dried green tea, fermented pu-erh tea contained high levels of methoxyphenolic compounds, such as 1,2,3-trimethoxybenzene, which was the most abundant one. Our results confirmed that the characteristic methoxyphenolic compounds were produced by the activity of Aspergillus during the post-fermentation process, and A. niger and A. awamori were the most important strains for the formation of aroma quality of pu-erh tea.展开更多
基金financially supported by the National Key R&D Program of China(2017YFD0400804)Public Technology Research Project of Zhejiang Province(LGN18C160001)Special Fund for Quality Research in the Public Welfare(20110210)to X.Yang。
文摘Repeated thermal treatment could impair the flavor of instant black tea(IBT)as the volatile compounds and characteristic constituents dramatically vary during the manufacturing process.Utilization of fresh leaves as raw material in IBT manufacture at low temperature may become an alternative to conventional extraction methods.This study aimed to improve the quality of IBT using fresh tea leaves by a two-stage enzymatic processing.The influence of combined enzymatic oxidation and extraction conditions for maximal extractable flavour(taste and aroma)characteristics from fresh tea leaves were investigated.The changes of aroma profiles and chemical constituents including theaflavins(TFs),thearubigins(TRs),theabrownines(TBs)and TRs/TFs ratio in converted tea brews under two-stage enzyme catalyzed fermentation and extraction conditions were further compared between different treatments,based on which the optimised conditions were determined.During the two-stage enzymatic processing,75 kinds of volatile compounds were identified in all processed samples,and the contents of TFs,TRs,TBs and TRs/TFs ratio could be optimized by adjusting different procedures and parameters.The overall properties of final product were compared with two types of commercial IBT.High quality IBT with desired properties and antioxidant activity can be manufactured using fresh tea leaves by two-stage enzymatic processing approach.
基金National Science Foundation of China(Grant No.81172944)National Key Technology R&D Program “New Drug Innovation” of China(Grant Nos.2012ZX09301002-002-002 and 2012ZX09304-005)
文摘Aroma is one of the most important factors for the flavor, taste, and quality of pu-erh tea, and the post-fermentation process has an important influence on the aroma of pu-erh tea. In the present study, the influence of fungi fermentation on the flavor of pu-erh tea was investigated and compared. Volatile compounds from pu-erh tea fermented by four Aspergillus strains, including A. niger, A. oryzae, /1. awamori, and A. glaueus, were extracted and analyzed using ultrasound-assisted extraction-dispersive liquid-liquid microextraction-gas chromatography-mass spectrometry （UAE-DLLME-GC-MS）, and a total of 63 volatile compounds were identified. In comparison with the sun-dried green tea, fermented pu-erh tea contained high levels of methoxyphenolic compounds, such as 1,2,3-trimethoxybenzene, which was the most abundant one. Our results confirmed that the characteristic methoxyphenolic compounds were produced by the activity of Aspergillus during the post-fermentation process, and A. niger and A. awamori were the most important strains for the formation of aroma quality of pu-erh tea.
