Effect Of Humidity Factor On The Cold Resistance Of Nitric Oxide (NO) Fumigated Hami Melon After Harvest

Hami melon(Cucumas melo L.)is one of the characteristic fruits of Xinjiang.The shape of the fruit is oval,the skin is light green,the seed cavity is small,the skin is tough,resistant to transportation,mature in high temperature and summer,the harvesting period is concentrated,and the fruit is piled up.Postharvest storage and preservation brings great pressure.At present,cryopreservation is one of the commonly used and effective methods.Because Hami melon(Cucumas melo L.)itself is a cold-sensitive fruit,the unpleasant low temperature tends to cause cold damage to the fruit,which seriously affects the postharvest quality of the fruit.In recent years,the research on the application of NO in the preservation of fruits and vegetables is extensive,but the effect of humidity factor on the storage quality of Hami melon is still less.Therefore,this studyselected Junxiu-Hami melon varieties in Kashi County,Xinjiang,using a concentration of 60 ?L/L NO,in low humidity(LH:35%?45%),medium humidity(MH:65%?75%)and high humidity(HH:90%?99%)The Hami fruit was fumigated.The chilling injury and quality parameters of cantaloupe fruit during storage at 3? were studied,and the optimal experimental group under optimal fumigation conditions was used to determine the activity of related enzymes and the study of cell wall metabolic pathways to explore the humidity factor and The effect of NO on the cold resistance of Hami melon fruit after harvest.The main findings are as follows:(1)Screen the appropriate humidity factors and study the relationship between NO and humidity factors and cold tolerance of Hami melon fruits.The Hami melon is treated by different humidity factors such as low humidity(LH:35%?45%),medium humidity(MH:65%?75%)and high humidity(HH:90%?99%).The experimental results show that under different humidity fumigation conditions,NO can delay the occurrence of chilling damage and quality deterioration of Hami melon(Cucumas melo L.).When the low humidity factor is 35%?45%,the cold tolerance of Hami melon during storage can be significantly improved.Compared with the control,the chilling injury of NO treatment group is delayed for 5 days,and the cold injury index is the lowest when it is stored for 30 days,only 40.00%;During the storage process,the fruit quality of the NO treatment group was better,and the hardness decreased slowly,which was 17.07 N,which was only 29.08%lower than the control group,and the cell membrane permeability increased only 24.11%;it could effectively maintain the high soluble solids.The content;delays the decrease of TA and Vc content of Hami melon(Cucumas melo L.)fruit;reduces the respiratory rate and ethylene release,and delays the peak occurrence time.It is clear that the humidity factor is one of the main factors affecting the effect of NO fumigation.In the condition of low humidity of 35%?45%,NO can better improve the cold tolerance of Hami melon(Cucumas melo L.)fruit and maintain a good storage quality.(2)Under the optimal treatment humidity conditions determined in the previous experiment,the effects of NO fumigation on postharvest reactive oxygen metabolism of Hami melon(Cucumas melo L.)fruit were investigated.Experiments show that NO has a significant promoting effect on antioxidant enzymes related to reactive oxygen species during storage.The SOD,POD,CAT and APX activities of the treated fruits were significantly higher than the control.It can effectively reduce the production rate of superoxide anion(O2·-)and the increase of chilling index.It is indicated that LH-NO treatment can improve the cold resistance of postharvest Hami melon(Cucumas melo L.)by enhancing the activity of related antioxidant enzymes.(3)The research proves that humidity and NO treatment have obvious preservation effect on fruits and vegetables.In this experiment,under the condition of low humidity of 35%?45%,further study on humidity factor and NO fumigation on postharvest softening of Hami melon(Cucumas melo L.)fruit.The effect between cold resistance.The results showed that when the humidity factor was 35%?45%,NO fumigation treatment could maintain the higher hardness of postharvest Hami melon(Cucumas melo L.)fruit and delay the softening process of fruit.Significantly inhibited the activity of PG and Cx,effectively increased the original pectin content of the fruit,delayed the decline of hardness;inhibited the cell membrane permeability and soluble pectin content.In summary,LH-NO can improve the storage quality of fruits after harvesting by regulating cell wall metabolism-related enzymes,and improve the cold tolerance of fruits,thereby prolonging the storage time of fruits.