Study On The Postharvest Refrigeration And Fresh-keeping Technology And Mechanism Of Chilling Injury Of Eggplant

Eggplant is one of the main vegetables in summer and autumn.The respiratory metabolism of eggplant was strong at ambient temperature after harvest.Improper storage and transportation can easily cause dehydration,rot,and deterioration.Low temperature refrigeration is often used to keep fresh,but eggplant will happen to chilling injury at unsuitable low temperature,which will affect the quality of eggplant seriously.In this paper,the‘Heiguan’eggplant was used as a test material to study the effect of storage temperature on preservation of postharvest eggplant stored with modified atmosphere package(MAP),intermittent warming combined with MAP on the chilling injury and storage quality of eggplant,as well as the mechanism of reducing chilling injury of eggplant by intermittent warming discussing from the cell wall,cell membrane,antioxidant system and relative expression of related genes.The results are as follows:1.The different storage temperature has a significant effect on the gas content in package bag,flesh color,peel firmness,appearance index,decay index and chilling injury index,as well as peroxidase(POD),catalase(CAT)and polyphenol oxidase(PPO)enzyme activities during the MAP storage process of eggplant after harvest(p<0.05).At 6℃and8℃,the degree of chilling injury of eggplant continued to increase with the storage time.Among them,eggplant at 6℃showed the earliest chilling injury and the most serious degree,and severe chilling injury symptoms appeared within 10 days.In the later period of storage,the gas in the treatment bags at 6℃and 8℃fluctuated greatly,the flesh color,peel firmness,activity of CAT and PPO were greatly reduced,activity of POD increased rapidly,the deterioration of quality was obvious,and the decay was serious.The commodity of eggplants stored with MAP at 12℃was the best.There was no chilling injury symptom within 20 days and the decay index was low.The storage quality remained good.2.The eggplant packaged with MAP was warmed intermittently in a cold storage at(6±0.5)℃once every 48 hours.The temperature of the eggplant was raised at 20℃for 24hours,four times in total.The control group was kept in a cold storage at(6±0.5)℃all the time during the storage period.The results showed that the intermittent warming treatment could significantly reduce the chilling injury index,decay index,respiratory intensity and free proline content during low temperature storage,and effectively maintain the appearance index,flesh color and firmness,delay the degradation of soluble sugar,soluble protein and phenol,reduce the occurrence of chilling injury during low temperature storage and maintain good quality of eggplant.3.The physical,chemical and molecular indexes of eggplant during storage after intermittent warming treatment were tested,the results showed that intermittent warming treatment can significantly inhibit the increase of the activity of polygalacturonase(PG)and cellulase(C_X),inhibit the degradation of protopectin and cellulose,maintain the integrity of cell wall structure,and reduce the softening degree of eggplant.The activity of lipoxygenase can be inhibited by intermittent warming treatment,and the accumulation of malondialdehyde(MDA)can be reduced,thus the lipid peroxidation of cell membrane can be inhibited and the cell membrane can be protected.Intermittent warming can significantly increase the activities of superoxide dismutase(SOD),POD,CAT and ascorbate peroxidase(APX),and induce the up regulation of SOD,POD and CAT genes expression,so as to scavenge active oxygen free radicals and enhance the chilling resistance of eggplant fruit.