Effects Of Pre-harvest CPPU And Post-harvest Ozone Treatments On Electrical And Physiological Characteristics Of Kiwifruit

Kiwifruit is populared by consumers because of its rich nutrition.In recent years,aim to increase the single fruit weight and yield,the application of CPPU in domestic kiwifruit production has become more and more common.However,the negative influences such as the decline in the quality,storability,and the resistance to disease of kiwifruit have also become more prominent.Ozone is a green preservative,which has significant effects in extending the storage period and maintaining quality of fruits and vegetables.In addition,kiwifruit is accompanied by energy transformation and metastasis in post-harvest ripening,senescence,decay and other processes,which leads to changes in the amount and spatial distribution of the charge within the cell.Macroscopically manifested as changes in electrical characteristics.The experiments used Qinmei and Hayward as raw materials to study the effects of pre-harvest CPPU and post-harvest Ozone treatments on the electrical and physiological characteristics of kiwifruit during low temperature storage,and pre-harvest CPPU treatment and weightlessness on the quality and electrical characteristics of kiwifruit during normal temperature storage.It provided a theoretical basis for non-destructive testing of kiwifruit treated with CPPU based on electrical properties.At the same time,it explored the mechanism of post-harvest Ozone treatment to reduce the adverse effects of pre-harvest CPPU treatment on kiwifruit through macroscopic electrical properties.The study obtained the following results:(1)Pre-harves CPPU treatment reduced the quality,accelerated fruit ripening,and was not good for storage of Qinmei kiwifruit.And pre-harvest CPPU treatment significantly reduced the quality of Hayward kiwifruit,but it could inhibit ’the fruit’s respiration rate,PG activity,and Cx activity.The treatment with CPPU pre-harvest and ozone postharvest improved the quality and physiological indicators of kiwifruit.However,the effect of Ozone treatment on Qinmei Kiwifruit was significantly better than Hayward Kiwifruit.(2)Both pre-harvest CPPU treatment and post-harvest Ozone treatment affected the correlation of quality,physiological parameters and electrical parameters of kiwifruit.The characteristic frequency of Qinmei’s normal fruit,inflated fruit,and Ozone treated fruit was selected as 3980 k Hz,0.1 k Hz and 3980 k Hz.The characteristic frequency of Hayward’s normal fruit,inflated fruit,and Ozone treated fruit was selected as 39.8 k Hz,3980 k Hz and0.1 k Hz.The common sensitive electrical parameter of Qinmei’s normal fruit and inflated fruit was Cp at the characteristic frequencies of 3980 k Hz and 0.1 k Hz.Cp was significantly correlated with VC,TA,PG,and Cx of normal fruit and inflated fruit,and had the strongest correlation with VC.A mathematical model of Cp and VC was established and the value of VC can be predicted by the equation.The common sensitive electrical parameter of Hayward’s normal fruit and inflated fruit was Lp at the characteristic frequencies of 39.8 k Hz and 3980 k Hz.Lp was significantly associated with the respiration rate,and the establishment of a mathematical model of both can be used to predict the value of respiration rate.It provided a theoretical basis for non-destructive testing of kiwifruit treated with CPPU based on electrical properties.For Qinmei kiwifruit,Ozone treated fruit had the same characteristic frequency as normal fruit,but different from inflated fruit.However,for Hayward kiwifruit,the characteristic frequency of Ozone treated fruit was inconsistent with both normal and inflated fruit.The macroscopic electrical properties indicated that post-harvest Ozone treatment can reduce the negative effects of pre-harvest CPPU treatment on kiwifruit.(3)Both CPPU treatment and weightlessness resulted in declining quality of kiwifruit during normal temperature storage.Weightlessness had a greater impact on the quality of Qinmei kiwifruit,and CPPU treatment had a greater impact on the quality of Hayward Kiwifruit.Among the 24 frequencies selected,the characteristic frequencies of Qinmei’s normal fruit,inflated fruit,and Hayward’s normal fruit,inflated fruit were respectively 3980 k Hz,1580 k Hz,631 k Hz,and 251 k Hz in the process of weightlessness at room temperature.The common sensitive electrical parameter of the four samples was Lp at the characteristic frequencies.The regression equation based on Lp and VC can be used to achieve non-destructive testing,so that the kiwifruit treated by CPPU can be selected.This has application prospect in actual production.The sensitive electrical parameters that can characterize the weightlessness rate were not screened out at the characteristic frequency of0.1 k Hz,so a mathematical model could not be established to achieve the non-destructive testing of freshness of kiwifruit.