Study On Changes Of The Aroma Components Of Tea Induced By H₂O₂ Produced By The Oxidation Of Catechins

In this study,GC-FID/MS and HPLC were used to study the mechanism of catechins oxidation to produce H₂O₂,and the possibility of H₂O₂-induced degradation of key volatile substances in green tea was further analyzed,with a view to clarifying the relationship between the oxidation of catechins—the accumulation of H₂O₂—the change of volatile components—the deterioration of aroma quality,which provided a theoretical basis and technical guidance for the regulation of aroma quality of green tea beverages during storage,and provided a certain reference significance for the processing and production of tea beverages and food.The main findings were as follows:1.Taking EGCG,the monomer with the highest catechin concentration in tea beverages,as the research object,the amount of H₂O₂ was measured under the reaction conditions such as the types of catechins,concentration,temperature,water bath time,metal ions,antioxidants,and pH by using a microplate reader method,and the results were further analyzed by analysis of variance.The test results showed that:?1?The order of the amount of H₂O₂ produced by catechin monomers such as EGCG,EC,ECG,EGC,and GA was EGCG>EGC>ECG>EC>GA,the amount of H₂O₂production was not always positively correlated with concenteation of catechins.There would be a downward trend when the amount of H₂O₂ produced by the system reached an equivalent concentration.At 37,50,70,and 90°C,the amount of H₂O₂ produced by EGCG gradually increased with the extension of the water bath time.?2?After adding metal ions including Fe²⁺and Cu²⁺to the EGCG solution,it was found that low concentrations of metal ions helped to promote the generation of H₂O₂ in the system solution,and once the concentration increased,which would help to inhibit the generation of H₂O₂ in the system solution.The oxidants including VC,BHA,BHT,and TBHQ contributed to the formation of H₂O₂ in the system solution,and the promotion effect of TBHQ was more significant,but it was not ruled out that the antioxidant itself may also generate H₂O₂.As the pH of the system solution increased,the amount of production of H₂O₂ was significantly increased.?3?With the increase of the water bath temperature under specific water bath conditions,the pH of the system solution gradually decreased,and the higher the concentration,the more obvious the decrease.And the content of EGCG showed a decreasing trend due to oxidative degradation of catechins,which promoted the formation of oxidative degradation products GCG ECG,CG,and GA.2.Taking the key volatile component linalool as the research object,the HS-SPME/GC-MS technology was used to study the effect of H₂O₂ on linalool under the reaction conditions such as the types of aroma monomers,concentration,mixing ratio,metal ions,pH,water bath temperature and water bath time,and the results were further analyzed by analysis of variance.The test results showed that:?1?5 kinds of aroma monomers including linalool,benzaldehyde,hexanal,linalool and?-ionone were treated with H₂O₂ and the concentration of linalool,linalool and?-ionone was reduced obviously,and the higher the concentration of linalool,the more obvious the effect of H₂O₂ on linalool,and as the concentration of H₂O₂ increaseed,the concentration of linalool first increased and then decreased.Among The ratio of H₂O₂ and linaloolin 1:3,2:2,and 3:1,the ratio of 2:2 made the aroma substances decrease more obviously.?2?The metal ions including Fe²⁺and Cu²⁺helped reduce the concentration of linalool,and the higher the concentration,the more the effect Obviously,and the more obvious the concentration decreased after adding H₂O₂.?3?H₂O₂ solution helped increase the concentration of linalool at a suitable pH,while the concentration of linalool would gradually decrease with the increase of pH.Heating time,temperature and the treatment of H₂O₂ all helped to reduce the concentration of linalool in the system solution.3.Taking the main catechin monomer EGCG and the key volatile component linalool as the research objects,microplate reader detection method,HS-SPME/GC-MS technology were used to study the effect of interaction between EGCG and linalool on the amount of H₂O₂ and the concentration of linalool under under the reaction conditions such as the temperature of water bath and metal ion conditions,and the results were further analyzed by analysis of variance.The test results showed that:?1?not only EGCG monomer could produce H₂O₂,but the addition of linalool could accelerate the formation of H₂O₂ on the basis of the former,and even increased the amount of H₂O₂ at normal temperature.?2?Compared with the control group without added metal ions,the EGCG monomer solution would significantly increase the amount of H₂O₂ after adding Cu²⁺.?3?Heating treatment would recduce the concentration of linalool,while adding EGCG afterwards would not have a significant effect on the linalool solution.?4?Adding metal ions to the solution helped increase the aroma concentration,and the presence of EGCG significantly affected the concentration of linalool,while Fe²⁺and Cu²⁺had the opposite trend.