The Effect Of UV-C Irradiation On Postharvest Quality And Antioxidant Activity Of Fragrant Pear

In recent years, there have been many studies about the correlation between the intake of fruit and vegetables and disease prevention and anti-aging. UV-C irradiation is a new method for postharvest treatment of fruit and vegetables which is simple for operation, no pollution, and in accordance with the requirement of green food. It is reported that UV-C treatment can improve the activity of defense enzyme and increase disease resistance of fruit and vegetables and promote the production of phenols and flavoniods. Fragrant pear produced in korla area is an economically important fruit in daily consumption. The aim of the paper is to study the effect of different doses of UV-C treatment on the quality and antioxidant system of fragrant pear.The effect of different doses of UV-C irradiation on the physical quality of fragrant pear during storage was investigated. After UV-C treatment, the storage quality and nutrients of fragrant pear were better kept. Firmness and weight loss rate is the important index of fragrant pear. The UV-C treatment delayed the decline of firmness and reduced the weight loss which means the UV-C treatment can better maintain the quality of the appearance of the fragrant pears during the storage. UV-C treatment can delay the peak of respiration and ethylene release. This experiment showed that UV-C is effective in keeping the content of total soluble sugar. Also UV-C treatment reduced the accumulation of MDA and delayed increasing of the cell membrane permeability. However, UV-C treatment has little effect on titratable acid and soluble solid content.Phenolics and VC are important antioxidants in fruits and vegetables. The experimental results show that the UV-C treatment tended to reduce content of VC in fragrant pear but this effect was not statistically significant. UV-C treatment can increase the content of phenolics in fragrant pear. The dose of3kJ/m2UV-C treatment resulted significantly increased secondary metabolism of total polyphenols and flavonoids. It also improved FRAP and DPPH free radical scavenge capacity. The effect of6kJ/m2UV-C treatment is not as good as3kJ/m-. The results showed that appropriate doses of UV-C treatment can improve the antioxidant capacity in postharvest fragrant pear.Numerous studies show that aging is closely associated with reactive oxygen species. Aging is the result of biological active oxygen accumulated in the body. SOD in plant disproportionated O2-as H2O2and O2, and the POD, CAT, etc tuned the H2O2into H2O, so as to relieve the ROS damage. Experiment showed that the mining of fragrant pear with APX, SOD, CAT enzyme activity are declining with the extension of storage time. After the declining ability of scavenging free radicals of fragrant pear, so that the activity of free radicals increased, membrane lipid peroxidation enhanced, fruit cell membrane was damaged. And UV-C treatment can delay the reactive oxygen species metabolism related enzymes.APX and SOD, CAT activity decreased, which is beneficial to the removal of the reactive oxygen species, so as to maintain the balance of active oxygen metabolism.PAL enzyme activity increased after UV-C irradiation which promoted the total phenol accumulation. The POD and PPO activity increased with the extension of storage time but UV-C irradiation treatment can delay the change. And the enzyme related to cell wall degradation of cellulose enzyme and beta-glycosidase enzymes reduced after irradiation treatment which means it is benefical to keep the firmness and the taste of fragrant pearThe high performance liquid chromatography (HPLC) method was used for monomer polyphenols content in the fragrant pear. The main phenolic acid compound in fragrant pear was chlorogenic acid and the main flavonoids substances was catechins and rutin. The phenolics content in the UV-C treatment group is higher than in the control group, while the phenolics content of3kJ/m2treatment group was higher than6kJ/m2treatment group.