Research On Mechanism Of Reducing Chilling Injury Of Eggplant With High Relative Humidity Storage

Eggplant has high nutritional value,postharvest metabolism of eggplant is vigorous,with a high rate of respiration and transpiration,and it is easy to lose water,shrink and rot.Therefore,some preservation measures should be taken to delay the deterioration of postharvest.Among them,low temperature storage is a widely used and effective way to keep fresh.But eggplant is a cold-sensitive vegetable and is vulnerable to cold damage during low temperature storage.The symptoms such as pitting rust on the surface and browning and blackening of internal flesh reduce the commercial value of eggplant.High relative humidity storage could significantly inhibit transpiration and tissue wilting of fruit and vegetable,which had a good application prospect in postharharvest cold chain storage.However,the effect of high relative humidity storage on chilling injury of eggplant has not been reported.To this end,the effects of dry fog controlled cold storage（4.0±0.5℃,96～99%RH）and low relative humidity cold storage（4.0±0.5℃,70～75%RH）on fruit quality,chilling injury,phenolics,reactive oxygen species,proline,and polyamine metabolism of eggplant were studied,in order to study the effect of high humidity storage on low temperature chilling injury of eggplant,and further explore its mechanism,so as to provide a theoretical basis for the application of dry fog controlled humidity storage in cold chain storage and transportation of postharvest eggplant.The main results are as follows:1.The effects of high relative humidity storage on fruit quality and phenolics metabolism of eggplant during low temperature storage were studied.Mild chilling injury symptoms appeared at 3 d in low relative humidity storage,and then the chilling injury index gradually increased.High relative humidity storage could significantly reduce water loss shrinkage and chilling injury symptoms of eggplant,maintain high fruit hardness,total phenolics and anthocyanin content,and maintain high commercial value.At the same time,the activity of phenolicis synthase such as PAL,C4H and 4CL was increased,promoted the expression of Sm PAL,Sm C4H1,Sm C4H2 and Sm4CL genes,improved its antioxidant capacity,increased the resistance of eggplant to low temperature.2.The effects of high relative humidity storage on reactive oxygen metabolism of eggplant during low temperature storage were studied.High relative humidity storage in inhibition of eggplant chilling injury at the same time,could effectively reduce relative conductivity and MDA content in fruit,improve the activity of SOD,APX,CAT,POD in antioxidant system,promote Sm Cu/Zn SOD,Sm APX,Sm CAT,Sm POD gene expression,inhibit H₂O₂ and O₂.^-generation,keep high-OH and DPPH free radical scavenging rate,greatly reduced the chilling injury of eggplant fruit.3.The effects of high relative humidity storage on proline and polyamine metabolism of eggplant during low temperature storage were studied.High humidity storage could increase the activities of proline synthase P5CS,OAT,polyamine synthase ADC and ODC,inhibit the activities of proline degradation related enzymes PDH and polyamine degradation related enzymes DAO and PAO,which was beneficial to the accumulation of proline and polyamine content in eggplant fruit,improve the cold resistance of eggplant,and reduce the occurrence of cold damage.