Study On The Change Of The Main Biochemistry,Aroma Components As Well As Their Influence On The Flavor Of Green Tea Beverages During Storage

Focusing on the change of the main biochemistry and aroma ingredients of green teabeverage, along with their correction, during storage.The following research works havebeen conducted: (1)The comparative study of the extracting method of aroma compoundsand HS-SPME was choosn as the best extracting method of aroma compounds fromgreen tea beverage. (2) The typical aroma compounds of XueYuan green tea and freeshgreen tea beverage was analysed and identified by GC-MS/GC-Olfactometry/RI methods.(3) The change of the main biochemistry and aroma ingredients of green tea beverage ,aswell as their correction and and their effect on the flavor of green tea beverage duringstorage. (4)Separation and analysis of the oxidation products of catechin in model systemand the effect of catechin oxidation on its anti-oxidant activity were also carded out,Themain results were as follows:1.The best extracting method and the optimum extracting conditionAmong the tested extracting methods of Simultaneously Distillation-Extraction(SDE),Head Space (HS) and HS-SPME, HS-SPME was the best for extracting aromacompounds from green tea beverage and the optimum extraction condition wasCAR/DVB/PDMS of extracting fiber,50"Cof extracting temperature, 60min ofextracting time, and 0.32g/mL of added sodium chloride, and 30mL of the head spacevolume.2.The typical aroma component of green tea beverageThe typical aromatic component of green tea beverage were: Linalool,Linaloloxide,Geraniol,Nerol,Nerolidol,(Z)-2-Heptenal,Benzaldehyde,Hexanal,Acetophenone,β-Lonone,Methyl salicylate,D-Limonene,2,5-Dibutyl-furan,which wereidentified by GC-MS/GC-O/RI methods. 3.The change of the main biochemistry and aroma components of green teabeverage,as well as their correction and their effect on the flavor of green tea beverageduring storage.The brightness of two kinds of green tea beverage (one added antioxidant, namedbeverage A,and the other wasn't, named beverage B) descended during storage, droped17.3% and 8.84%, respectively. Colour of the two kinds of beverage became yellow red;and the aroma of the beverages all reached the best in the 10th month of storage.Thebeverages appeared slight sourish odor in the last two months of storage.The main biochemistry ingredients of green tea beverage changed prominentlyduring the storage.The relative concentration of total polyphenol of beverage A andbeverage B decreased 26.6% and 9.01%, respectively,The concertration of EGCG alsodescended obviously.In the first month of storage,the concentration of catechin inbeverage A droped rapidly.However, it almost did not change in beverage B,but afterstoring for 6 months,the loss ratio of catechin in beverage A and beverage B were 57.2%and 64.3% respectively. During storage, there were amount of H₂O₂ produced in bothbeverages, and the concentration of H₂O₂ changed regularly. Which may be corrected tothe oxidation of catechins;The concentration of dissociative amino acid (AA) in twokinds of beverage changed regularly,too. After storage for one month,the concentrationof AA in the beverage A descended obviously, about 68% of which was lost. However, itincreased after the 4th month of storage.For beverage B, the change trend of AA wasconsistent with that of beverage A after the first month of storage, except that it changedindistinctively in the first month of storage.The main aroma components of green tea beverage also changed prominentlyduring storage.After storage,the kinds and concentrations of aroma components of bothbeverages increased obviously, and the relative contents of the presentative aromaticcompounds in both beverages increased dramatically.For example all of, the relativecontents of Linalool,Linalol oxide,Geraniol,β-Lonone increased dramatically duringthe whole storage time.However, the concentration of Hexanal,Benzaldehyde and Nerolof the beverage A descended smally in the 10th month.Correction between the change of the main biochemistry ingredients and the change of aroma of green tea beverage during storage was analysis by SAS software, and theresults showed that they had positive correlation. The oxidation of catechin and thechange of H₂O₂ lead to the increase in concentration of Linalool,Linalol oxide,Geraniol,β-Lonone,Benzaldehyde and Nerol;The change of AA and H₂O₂ lead to theconcentration increase of Hexanal. The oxidation of catechins was confirmed as adominant factor which lead to the change of aroma of tea beverage during storage bymultiple gradually regression analysis,and model system.4.Separation and analysis of the oxidation products of catechin in model system andthe effect of catechin oxidation on its anti-oxidant activityOne oxidant product (m/z471) and its dimer (m/z939) of tea catechin was wereseparated from H₂O₂ model oxidation system by multiple multistage columnchromatograph.HPLC-MS analysis showed that it was a product of EGCG by theelimination of 2H and adding a atom of oxygen.The anti-oxidized activity of oxidation products and tea polyphenol in differentsystems were mensurated. The results showed that the oxidant products of catechin hadvery strong antioxidant activity in all tested systems.The scavenging effect of the oxidantproducts on hydroxyl free radical(·OH) in methyl violet color metric system,DR system,salicylic acid system were 96.46%,84.8%,81.9%,respectively;The scavenging effect ofthe oxidant products on superoxide anion (O₂^-·) in luminescence of Pyragollicacid-Luminol system was 97.0%. and the antioxidant activity of the oxidant products wasmuch stronger than that of tea polyphenol in the same concertration in all tested systems.