| White tea is a unique type of tea in China.It is one of the six major teas.It is mainly produced in Fujian Province.In recent years,Yunnan Province has also begun to produce and process white tea on a large scale.White tea is not fried or kneaded during processing.The unique quality is deeply loved by consumers at home and abroad.For a long time,researchers have focused on Fuding white tea and Zhenghe white tea.There are few studies on Yunnan white tea,especially the quality changes of Yunnan white tea after storage.Therefore,this paper proposes to analyze the quality differences of white tea with different storage time in Yunnan and Fujian.In this paper,Jinggu white tea from Yunnan and Fuding white tea,Zhenghe white tea from Fujian were used as the research objects.The storage time was the new tea of the year(2022),storage for 1 to 3 years(2021,2020,2019)and storage for 15 years(2007),respectively.The physical and chemical components were detected and sensory evaluation was carried out.The volatile components in different varieties of white tea and white tea with different storage time were analyzed by headspace solid phase microextraction(HS-SPME)and gas chromatography-mass spectrometry(GC-MS),and the quality differences of white tea with different storage time in the two places were compared.The results are as follows :The 2022 tea samples of three kinds of white tea were analyzed.The results of sensory evaluation,physical and chemical composition detection and volatile component detection showed that there were differences among the three kinds of white tea.Sensory evaluation showed that the appearance of Jinggu white tea was grayish brown,while Fuding white tea and Zhenghe white tea were silver gray green and gray green,which reflected the appearance characteristics of Jinggu white tea ’black back and white face’.In terms of aroma,Fuding white tea and Zhenghe white tea are more intense than Jinggu white tea,while Jinggu white tea has a more pure aroma.Fuding white tea and Zhenghe white tea were light apricot yellow,Jinggu white tea was light honey yellow,which was darker than Fuding white tea and Zhenghe white tea.The taste of the three kinds of white tea is basically the same,but Fuding white tea and Zhenghe white tea with bitterness;fuding white tea and Zhenghe white tea are yellow-green,while Jinggu white tea is yellow-brown.The main physical and chemical components of different varieties of white tea are different.The contents of water extract,total catechins,tea polyphenols and flavonoids in Jinggu white tea were higher than those in Fuding white tea and Zhenghe white tea.The contents of amino acids and caffeine in Fuding white tea and Zhenghe white tea were higher than those in Jinggu white tea.The difference in the content of these substances makes the taste of the three white teas different.The water extract Jinggu white tea is the highest,so the taste is mellow,while the amino acid content of Fuding white tea is the highest,so the taste is fresh.The content of caffeine Fuding white tea and Zhenghe white tea is higher than that of Jinggu white tea,so the taste is bitter.The results of GC-MS analysis showed that 88 volatile substances were identified in different varieties of white tea,55 aroma substances were detected in Fuding white tea,55 aroma substances were detected in Jinggu white tea,and 51 aroma substances were detected in Zhenghe white tea,among which alcohols,aldehydes,esters,hydrocarbons and ketones were the main aroma substances.Alcohols and aldehydes are the main aroma components of white tea,among which linalool and its oxides,benzyl alcohol and nonanal are the main aroma components.The relative content of hydrocarbons in Jinggu white tea was significantly higher than that in Fuding white tea and Zhenghe white tea.The relative content of alcohols in Jinggu white tea and Zhenghe white tea was similar,and that in Fuding white tea was lower.The relative content of aldehyde compound Fuding white tea was the highest,followed by Zhenghe white tea,and Jinggu white tea was the lowest.The contents of the other three kinds of white tea were similar.The differences in these volatile substances created the aroma differences of the three white teas.In addition to the floral aroma substances,the relative contents of fruity and sweet aroma substances in Fuding white tea and Zhenghe white tea were greater than those in Jinggu white tea.Therefore,the aroma of Fuding white tea and Zhenghe white tea was stronger than that of Jinggu white tea,while Jinggu white tea showed more pure floral aroma.The physical and chemical components,sensory evaluation and volatile substances of white tea changed during storage.In the sensory evaluation,the color of the three kinds of white tea gradually became darker and grayish brown after storage.From floral and fragrance gradually transformed into fruity,medicinal fragrance;the color of the soup gradually deepened and became honey yellow;the umami taste disappears and becomes sweet;the color on the bottom of the leaf deepened and the softness decreased.With the increase of storage time,the contents of water extract,catechins,amino acids,soluble sugar and tea polyphenols showed a decreasing trend.The change of caffeine was not obvious after short-term storage,but decreased significantly after long-term storage,while flavonoids increased significantly.The change rate of water extract content of Fuding white tea was the largest,and that of Jinggu white tea was the smallest.The change of tea polyphenol content.The decline rate of Jinggu white tea was the highest,and that of Fuding white tea was the lowest.The change of flavonoids content The growth rate of Fuding white tea was the highest,and the growth rate of Jinggu white tea was the lowest.The change of amino acid content The decline rate of Fuding white tea was the highest,and the decline rate of Zhenghe white tea and Jinggu white tea was close.The decline rate of three kinds of white tea catechins was close.The change of caffeine content The decline rate of Fuding white tea was the highest,and the decline rate of Zhenghe white tea and Jinggu white tea was close.The decrease rate of soluble sugar content in Dingbai tea was the highest,and the decrease rate of Zhenghe white tea and Jinggu white tea was close.The change rate of most physical and chemical components of Fuding white tea and Zhenghe white tea was greater than that of Jinggu white tea,and the aging of Fujian white tea was faster than that of Jinggu white tea.The changes of the main volatile components of the three kinds of white tea with different storage time were similar.After short-term storage,the substances with clear aroma and umami slowly decreased,and the substances with woody aroma and presented began to appear or increase.The stale aroma and woody aroma of white tea stored for 15 years appeared,and the relative content of alcohols decreased significantly.During the storage process,the contents of linalool,geraniol,methyl salicylate,phenylethyl alcohol and other components with clear flower aroma decreased,so that the freshness and fragrance of white tea gradually decreased or even disappeared.The increase in the content of cedrol,2-methylnaphthalene,cedar wood,cedar wood,and other aged aroma substances may be the material basis for the aged white tea aroma.In addition,the coordination of benzaldehyde,fruity,floral,wood-flavored β-ionone,leaf-flavored,fruit-flavored geranyl acetone,etc.,together formed the characteristics of the aged white tea with jujube,medicine,and plum aroma during storage.The conversion rate of aged aroma substances in Fuding white tea and Zhenghe white tea was higher than that in Jinggu white tea,so the two kinds of white tea in Fujian were more likely to have aged aroma. |
