Effects Of De-astringency From Persimmon By Different Carbon Dioxide And Ethanol Treatments

Fruits of persimmon cv.‘Zaohong’ were treated with different concentration of carbon dioxide andalcohol. The effects of deastringency in different treatments on the soluble tannin content,fruit quality,chloroplast pigment content, ADH, PPO enzyme activity and active oxygen species were studied.Theresults as follows:1It was found that the treatments with30%ethanol,40%ethanol and80%carbon dioxide canremove astringency completely in96hours at room temperature. The alcohol treatmen could reduce thesoluble tannin content more effective than the carbon dioxide treatment. Furthermore, the activity ofalcohol dehydrogenase（ADH） and polyphenol oxidase（PPO） were investigated during the de-astringentprocess. The result showed ADH activity increased to the its peak levels, and then decrease, while PPOactivity gradually increased in the treatment..2Titratable acid and chloroplast pigment content of persimmon fruits showed a gradual downwardtrend and soluble sugar at first decreased within the first48hours and then increased but the treatmentof carbon dioxide and alcohol presented different trend during treatment process; vitamin C increasedslightly at first and then decreased; chloroplast pigment content decreased; carotenoid content increased.It was suggested that treatment of carbon dioxide has more effect on fruit quality and chloroplastpigment than alcohol treatment, and the effect is better when the concentration of carbon dioxidehigher.3The change of MDA content, O^2-net generation rate, SOD, POD, CAT activity in fruits ofpersimmon cv.‘Zaohong’ were studied during the de-astringency treatment of carbon dioxide.Theresults showed that the MDA content raised in the earlier stage and then declined, and it took less timereaching the summit in the treatment with the higher concentration of CO₂; the net generation rate of O^2-showed a increase trend and decreased only in70%and80%CO₂treatment during late stage; the SODactivity increased at more significant rate during late stage than early stage, the higher the concentrationof CO₂was, the higher the SOD activity was; the POD activity raised in the early stage then declined.The changes of SOD activity with70%and80%CO₂treatment were similar, and the higher activitywas associated with the lower concentration of CO₂; The higher CAT activity was observed in thehigher concentration of CO₂treatment during early stage, whereas the lower activity during latedeclined stage. The studies suggested that the changes of active oxygen metabolism showed the sametrend as that of tannin content and fruit quality in previous studies. CO₂was the main affecting factorsof active oxygen metabolism, it has a positive effect on de-astringency treatment of carbon dioxide inpersimmon.