Study On Quality Change And Preservation Technology Of Fuliang Green Tea During Storage

There are many reports ahout green tea quality change during processing,but few studies ahout green tea change quality during storaging.In order to explore the flavor substances changes of Fuliang green tea during storaging and provide theoretical and technical support for its fresh-keeping,this paper mainly studied five aspects:(1)the flavor substances change of Fuliang Green Tea during storaging;(2)the effect of different preservative on Fuliang Green Tea during storaging;(3)the effect of different package on Fuliang Green Tea during storaging;(4)the effects of different preservative and package on Fuliang Green Tea during storaging;(5)Design of green tea preservation and transfer warehouse.This paper takes Fuliang Green Tea as the research object.Firstly,the quality change of Fuliang Green Tea during storage was studied,and the flavor substances change and the influence of green tea quality were analyzed during storaging.Then,by using different preservation technologies(preservative,package and their composite),the better preservation technology of green tea was obtained.Finally,a green tea storage was established based on the preservation technology.The research methods,main results and conclusions are as follows:1.Flavor substances change of Fuliang Green Tea during storaging.Five non-volatile components(water,tea polyphenols,caffeine,amino acids and total sugars)and volatile components closely related to the quality of green tea were selected.First,their non-volatile components were determined and analyzed.Then GC-IMS combined with HS-SPME-GC-MS were used to detect the volatile compounds,and ROAV was used to analyze the changes during storaging.The results showed that polyphenols and caffeine contents decreased gradually during storaging.The soluble total sugars and free amino acids contents increased first and then decreased gradually,and both reached the maximum in the third month.Except for cysteine,the other free amino acids content decreased gradually.56 and 64 VOCs were identified by GC-IMS and HS-SPME-GC-MS,respectively.During storaging,the rich linalsol and its oxides,geraniol,heptanal,β-ionone,nonaldehyde,3-hydroxy-2-butanone and methyl salicylate gradually decrease or even disappear,and all have positive contribution to the green tea aroma.However,some substances that have negative effects on green tea aromare gradually produced,such as chrysanthemum alcohol,9-acetoxy-nonaldehyde,2-octanone,3-ethyl-1H-pyrazine and 2,5-dimethylpyrazine.PCA results based on GC-IMS can distinguish green tea samples with different storage time.ROAV results based on GC-MS showed that the ROAV of linalool,dimethyl sulfur,nonaldehyde,geraniol,jasmonone,(E,E)-2,4-nonenal and Δ-juniene were significantly different in different storage time samples.Considering the increase of cysteine and the decrease of linalool oxide during storage,oxidation may not be the only factor contributing to the decline in tea quality.2.Effect of different preservative on Fuliang Green Tea during storaging.In this study,several representative preservatives on the market were selected,and the composite preservatives of desiccants and deaerators to conduct accelerated aging test of green tea.The preservation effects of these preservatives were compared from six different index substances(water soluble,polyphenols,soluble total sugars,total free amino acids,caffeine and flavonoids).The experimental results showed that,in terms of the retention amount of all indexes,all indexes contents in the green tea group after adding preservative were higher than those in the control group,so the fresh-keeping effect after adding preservative was very obvious.The different preservative had different fresh-keeping effects,among which the three compound preservative agents of color-changing silica gel+vitamin c,color-changing silica gel+iron powder or sodium metabisulfite + vitamin c had better fresh-keeping effects.3.Effect of different package on Fuliang Green Tea during storaging.In this study,several representative packages on the market were selected to conduct accelerated aging test of green tea,and their preservation effects were compared from six different index substances(water soluble,polyphenols,soluble total sugars,total free amino acids,caffeine and flavonoids).The results showed that the preservation effect of green tea was closely related to the selection of packages.The preservation effect of double-layer or three-layer composite packages was better than that of single-layer package.The preservation effect of green tea was the best when it was packaged with AL/PA or PET/PE.4.Effects of different preservative and package on Fuliang Green Tea during storaging.In this study,several preservative agents(color-changing silica gel+vitamin c,color-changing silica gel+iron powder and sodium metabisulfite+vitamin c)and packages(AL/PA and PET/PE)with good preservation effect were selected as a pair to conduct accelerated aging test of green tea.Their preservation effects were compared from six different index substances(water soluble,polyphenol,soluble total sugar,total free amino acid,caffeine and flavonoids).The results showed that the preservation effect of different preservative and packages was different in terms of the retention of various indexes.Among them,the preservative effect of green tea was the best after the combination of sodium metabisulfite and vitamin c was added and then packaged with PET/PE.5.Design of green tea preservation and transfer warehouse.Based on the preliminary design of green tea preservation and transfer storage,including site selection,workshop layout,process flow and structural characteristics analysis of the transfer storage.This study determined the kinds of preservatives and packages,completed the layout of green tea preservation and transfer storage,related equipment selection and related drawings.And carry on the transfer warehouse structure characteristic and the process flow analysis.The green tea preservation and transfer warehouse with a total capacity of 72 tons was established,which could slow down the rate of change of bad tea and prolong the shelf life of tea,thus improving the economic value of tea.