Study On Postharvest Storage Characteristics And Ripening And Softening Mechanisms Of Two Kinds Of Muskmelon Fruits With Thin Skin

The thin-skinned melon(Cucumis melo var.makuwa Makino)is an annual creeping herbaceous plant in the family Cucurbitaceae and genus Cucumis.The northwest arid region is a dominant production area for melons with unique advantages of light and heat resources,producing high-quality melons that have become one of the important economic crops locally.However,the typical respiratory climacteric fruit of the melon is prone to sandification and deterioration after harvest,with a short storage period and significant shelf loss,so it is of great significance to understand the post-harvest storage characteristics and possible maturity aging mechanism of melons and explore preservation measures.This experiment studied two geographical indication agricultural products,Black Willow "White Pear Crisp" and Wuyuan "Lantern Red," in the Hetao region of Inner Mongolia.Mature(7-8 maturity)fruits were used as 2materials and were subjected to ambient temperature(25±2℃)and low temperature(8±1℃)treatments to observe the changes in external morphological characteristics,nutritional quality,and softening-related indexes during storage,aiming to understand the storage characteristics and possible softening mechanism of the two melon varieties and providing theoretical support and technical support for scientific and reasonable post-harvest preservation measures.The results are as follows:(1)Under ambient temperature storage conditions,the unique appearance and quality of ’White Pear Crisp’ melons gradually formed on the 3rd day after harvest and continued until the 7th day of storage.With the extension of storage time,brown spots and mold spots appeared on the fruit surface,the fruit skin began to shrink,the texture gradually sandified,and the external appearance quality of the fruit significantly declined.The ’Lantern Red’ fruit was of the best quality on the 1st day of storage,and the external appearance quality of the fruit started to decline after 3 days of storage,manifested as the fruit skin wrinkling and turning gray,with the appearance of brown spots.With the extension of storage time,the flesh texture quickly sandified and softened,and an unusual odor was emitted.Low-temperature conditions can significantly delay the decline in the external appearance quality of the two melon varieties.(2)Throughout the entire storage period,the content of soluble solids,soluble sugars,soluble proteins,and vitamin C in the two melon fruits increased in the early storage period and decreased in the late storage period as storage time extended.Under low-temperature conditions,the change trend of the nutritional substance content of the two fruits was consistent with that under ambient temperature conditions,but the change process was slowed down.(3)Throughout the entire storage period,the changes in peroxidation-related indicators of the two melon fruit membranes were similar.The malondialdehyde(MDA)content and relative conductivity of the two varieties of melon fruits gradually increased with the extension of storage time.The LOX activity of ’white pear crisp’ fruit increased gradually with the extension of storage time.The LOX activity of ’lantern red’ fruit showed a trend of increasing in early storage period and decreasing in late storage period.The MDA content,relative conductivity,and LOX activity of the two varieties of melon fruits demonstrated lower values under low-temperature treatment than under ambient temperature treatment,indicating that low temperatures can inhibit the peroxidation of fruit cell membranes.(4)Throughout the entire storage period,the water-soluble pectin(WSP)content of the two melon varieties gradually increased,while the flesh hardness and cellulose content gradually decreased.At room temperature,the PG enzyme activity of the two fruits increased gradually with the extension of storage time,while at low temperature,the PG enzyme activity showed a fluctuation trend of first decreasing,then increasing and then decreasing.The performance of fruits under low temperature treatment was better than that under normal temperature treatment,indicating that temperature was the key factor affecting the degradation of fruit cell wall components.(5)The correlation analysis between melon fruit hardness,sugar,cell wall components,and related softening enzymes under ambient temperature conditions showed that the fruit hardness of White Pear Crisp was significantly positively correlated with the content of soluble sugar,MDA content,WSP content,PG,and LOX activity and significantly negatively correlated with the cellulose content.The fruit hardness of Lantern Red was significantly negatively correlated with the content of soluble sugars and LOX activity and significantly positively correlated with the cellulose content.This indicates that cellulose content is an important component for maintaining fruit hardness.The mechanisms of melon softening are different for different varieties.In summary,it can be concluded that White Pear Crisp has better storage durability than Lantern Red.