Effects Of Vacuum Combined With Tea Polyphenols Impregnation On Quality Characteristics Of Kyoho Grape During Storage

Grapes are rich in nutrition and are deeply loved by people.However,grapes are soft and juicy.Due to transpiration,metabolic activities,and microbial attack during postharvest storage and transportation,they are easily softened and shrunk,browned and rotted,which greatly restricts the development of the table grape industry in China.Therefore,looking for the green and efficient post-harvest storage technology is still a hot research topic today.In this paper,effects of vacuum impregnation combined with tea polyphenol(VI-TP)on quality and impregnation properties of Kyoho grapes were investigated.Meanwhile,the material transfer during vacuum impregnation were modeled.In addition,effect of VI-TP on the physical and chemical quality,enzyme activity,pectin and anthocyanins of Kyoho grapes during storage was studied.Effect of VI-TP on the structural properties of pectin and anthocyanins of Kyoho grapes during storage were also investigated.According to these results,VI-TP preservation technology of Kyoho grapes was established and its mechanism was also revealed.The results were as follows:(1)Effects of vacuum combined with tea polyphenols impregnation on quality and impregnation properties of Kyoho grapes: The quality and impregnation properties of Kyoho grapes were investigated with VI-TP,and the material transfer during vacuum impregnation was modeled.The maximum effective porosity and impregnation volume fraction were obtained with 5k Pa vacuum treatment at 20 °C for 15 min,and the best impregnation level was obtained.In addition,the hardness of grapes was the highest with such impregnation conditions.Moreover,the activities of polyphenol oxidase and peroxidase in fruit were lower,while the activity of phenylalanine ammonia-lyase was higher.The content of tea polyphenols and anthocyanins was higher,and grape color also was better at these impregnation conditions.The results of the research on mass transfer of vacuum impregnation combined with tea polyphenol process showed that Azura model,Penetration model and Magee model can better predict the water loss and solids acquisition during the vacuum impregnation process of grapes.(2)Effects of vacuum combined with tea polyphenol impregnation on physics and chemistry quality of Kyoho grapes during storage: The physical and chemical quality of Kyoho Grapes were researched with VI-TP during storage.Compared with control(CK),vacuum impregnation group(VI)and normal pressure impregnation tea polyphenols group(AI-TP),vacuum combined with tea polyphenols impregnation(VI-TP)treatment can effectively inhibited the decrease in hardness and chew ability of Kyoho grapes,and maintained higher fruit springiness.At the same time,the weight loss rate and decay rate of Kyoho grapes during storage were also effectively suppressed by VI-TP treatment.In addition,higher soluble solids(SSC)and titratable acid(TA)content were observed in VI-TP treated fruits.VI-TP also improved the colour and lustre of Kyoho grapes.The results showed that VI-TP could effectively maintain the physical and chemical quality of grape fruits during storage.(3)Effects of vacuum combined with tea polyphenol impregnation on pectin and polyphenols of Kyoho grapes during storage: The pectin,polyphenols and related enzyme of Kyoho grapes were studied with VI-TP during storage.Compared with CK,VI and AI-TP,VI-TP treatment effectively inhibited the activities of polyphenol oxidase(PPO),peroxidase(POD),pectinomethylesterase(PMG)and polygalacturonase(PG)of Kyoho grapes during storage.High phenylalanine aminotransferase(PAL)activity of Kyoho grapes with VI-TP was maintained.In addition,the higher total phenol and anthocyanin content and antioxidant capacity of Kyoho grapes during torage were also effectively maintained by VI-TP treatment.At the same time,the higher contents of water-soluble pectin(WSP),chelating pectin(CSP)and alkali soluble pectin(SSP)were observed in VI-TP treated fruits.(4)Effects of vacuum combined with tea polyphenol impregnation on the structural properties of pectin and anthocyanins of Kyoho grapes during storage: The structural properties of pectin and anthocyanins in Kyoho grapes were investigated by the high performance liquid chromatography(HPLC),liquid mass spectrometry(HPLC-MS),Fourier infrared spectroscopy(FTIR)and nuclear magnetic resonance(NMR).Compared with CK,VI,and AI-TP,VI-TP treatment could effectively inhibit the degradation of CSP and SSP of Kyoho grapes during storage,and maintained the higher molecular weight and structural integrity of pectin.At the same time,VI-TP treatment inhibited the degradation of anthocyanins of Kyoho grapes during storage.The HPLC-MS,FTIR and NMR results of the pectin-anthocyanin polymer showed that the cross-linking between the non-esterified groups of pectin and anthocyanins increased the esterification degree of pectin chain.The high degree of methyl esterification of pectin made the fruit have a better texture,which is conducive to the storage of grapes after harvest.