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
Amyloid is the term usually used to describe a particular type of elongated,unbranched protein fibril with cross-β-sheet characteristics,formed through the ordered aggregation of peptides or denatured proteins.Amyloi...Amyloid is the term usually used to describe a particular type of elongated,unbranched protein fibril with cross-β-sheet characteristics,formed through the ordered aggregation of peptides or denatured proteins.Amyloids show high association with many severe neurodegenerative diseases,such as Alzheimer's,Parkinson's,and Huntington's diseases.Unfortunately,there are still no effective medical treatments to cure these neurodegenerative diseases,including the failure of pharmaceutical approaches with amyloids as the targets.Polyphenols,the major phytochemicals in fruits,vegetables,tea and coffee have many beneficial functional properties,such as antioxidant,antimicrobial and anticancer properties.Polyphenols can interact with proteins through non-covalent interactions,including hydrophobic interaction,hydrogen bonding and electrostatic interaction.Polyphenols can also covalently interact with proteins mainly via the interaction between quinones,the oxidized products of polyphenols,and the nucleophilic residues(thiol,amino,guanidine,or imidazole)in protein side chains or peptides.Evidence from previous studies have indicated that polyphenols could reduce amyloid-formation via inhibiting fibril aggregation or steering oligomer formation into unstructured,nontoxic pathways.This effect was realized mainly through:(1)preventing conformational changes of precursor native proteins into amyloidogenic forms,(2)inhibiting the conversion of amyloidogenic precursors to amyloid fibrils,or(3)disrupting preformed fibrils meanwhile destructing the aggregation conditions.These findings imply that polyphenols could play a vital role in inhibiting protein misfolding,which might be useful for the prevention of various neurodegenerative diseases.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funded by the National Natural Science Foundation of China (No.31901760,No.31871843)the Natural Science Foundation of Jiangsu Province—Distinguished Youth Foundation (BK20200022)+4 种基金the Natural Science Foundation of Jiangsu Province—Youth Foundation (BK20190530)Jiangsu Agricultural Science and Technology Innovation Fund (CX (21)3040)Laboratory of Lingnan Modern Agriculture Project (NZ2021034)the Fundamental Research Funds for the Central Universities,China (KJJQ202102,KYDZ201903)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Amyloid is the term usually used to describe a particular type of elongated,unbranched protein fibril with cross-β-sheet characteristics,formed through the ordered aggregation of peptides or denatured proteins.Amyloids show high association with many severe neurodegenerative diseases,such as Alzheimer's,Parkinson's,and Huntington's diseases.Unfortunately,there are still no effective medical treatments to cure these neurodegenerative diseases,including the failure of pharmaceutical approaches with amyloids as the targets.Polyphenols,the major phytochemicals in fruits,vegetables,tea and coffee have many beneficial functional properties,such as antioxidant,antimicrobial and anticancer properties.Polyphenols can interact with proteins through non-covalent interactions,including hydrophobic interaction,hydrogen bonding and electrostatic interaction.Polyphenols can also covalently interact with proteins mainly via the interaction between quinones,the oxidized products of polyphenols,and the nucleophilic residues(thiol,amino,guanidine,or imidazole)in protein side chains or peptides.Evidence from previous studies have indicated that polyphenols could reduce amyloid-formation via inhibiting fibril aggregation or steering oligomer formation into unstructured,nontoxic pathways.This effect was realized mainly through:(1)preventing conformational changes of precursor native proteins into amyloidogenic forms,(2)inhibiting the conversion of amyloidogenic precursors to amyloid fibrils,or(3)disrupting preformed fibrils meanwhile destructing the aggregation conditions.These findings imply that polyphenols could play a vital role in inhibiting protein misfolding,which might be useful for the prevention of various neurodegenerative diseases.
