Study On The Factors Affecting The Acidification Of Congou Black Tea During Storage

Congou black tea is the main black tea categories produced in our country,which was developed well in recent years.However,different degrees of acidification occurred during storage of Congou black tea,which affected its taste quality.In this paper,the factors and mechanism of acidification in the storage process of Congou black tea were studied mainly from the process and storage conditions,in order to provide theoretical basis for the optimization of processing technology and storage conditions of Congou black tea.1.The effect of aroma-enhanced technology on acidification during storage of black teaThe effects of different aroma-enhanced temperature(80℃,130℃)and differentaroma-enhanced times(1,2,3 times)on acidification of Congou black tea during storage were studied.The results of sensory review and electronic tongue analysis showed that,compared with the tea samples without fragrance,the acidity and astringency of tea infusion increased with the increase of fragrance temperature and frequency,while the sweetness decreased significantly,and the composition ratio of flavor types changed obviously.The results of UPLC-Q-TOF/MS and HPLC analysis showed that the contents of soluble sugar and amino acid were significantly reduced after aroma-enhanced treatment,especially the contents of sweet and umami amino acids,flavonoid glycosides and aroma glycosides were reduced,while the contents of oxalic acid,malic acid,quinic acid and ester catechin were increased,indicating that the composition of taste substances had changed.Further through the in vitro simulation experiment,it was found that the contents of oxalic acid,malic acid and quinic acid in tea with exogenous aromatic amino acids and glucose increased significantly after being raised at 130℃.The possible ways to accelerate acidification during storage of black tea by the process of improving aroma are as follows: The decomposition of sugars and amino acids after heating will produce organic acids,and some aldehydes and alcohols in Congou black tea are slowly transformed into organic acids during storage.These reasons lead to an increase in the total acidity of Congou black tea.Meanwhile,the process of fragrance and storage leads to a decrease in the content of taste substances in tea,which changes the composition of tea taste and leads to acidification of tea infusion.Production is suggested to control the temperature and frequency of enhanced-aroma,in order to enter the market before enhanced-aroma is appropriate.2.Influence of storage technology on acidification of black teaThe effects of different storage temperatures(room temperature 17-25℃,cold storage 0℃,freezing-20℃)on acidification of Congou black tea were studied.The results showed that the contents of polyphenols,amino acids and soluble sugars decreased significantly with the increase of storage temperature.Total acid content increased significantly and p H decreased significantly.The accumulation of oxalic acid,quinic acid and gallic acid during storage and the decrease of the contents of tea polyphenols,amino acids,soluble sugars and other taste substances are likely to be the main reasons for acidification of tea stored at normal temperature,and the preservation at lower temperature can effectively delay the acidification of black tea during storage.Compared with old black tea,young black tea has lower acid content in old black tea.The reason for the lack of acidity may be that the total acid content in the sample is not enough to reach a certain sensory threshold.Secondly,the old raw material itself has a high content of soluble sugar,which may effectively balance the taste of tea soup,so it is not easy to occur obvious acidification in the storage process.The effects of different oxygen content(nitrogen filling,vacuuming,conventional),different air humidity(high humidity,low humidity)and different packaging materials(thin aluminum foil bag,thick aluminum foil bag,plastic ziplocking bag)on acidification during storage of Congou black tea were compared.The results showed that acidification of Congou black tea during storage was closely related to the reduction of polyphenols,amino acids,flavonoids and soluble sugars,and the absence of taste substances was the main reason for the prominent sour taste of black tea.Low temperature(below 0℃),low humidity and nitrogen filling are the main methods to effectively delay acidification during storage of Congou black tea,which can better maintain tea quality.