Effects of Ultrasonic Pretreatment on Texture,Pectin Properties,and Pectinase Activity of Kiwifruit During Storage
After harvest,kiwifruit undergoes rapid softening and quality changes,significantly affecting its economic value.In order to extend its storage period,ultrasound(US)technology was applied in the pre-storage treatment of kiwifruit.The study investigated the effects of different treatment times(10,20,30 min)on the textural properties,pectin characteristics,and pectinase activities of kiwifruit during storage,followed by a correlation analysis.The results indicated that kiwifruit treated with US for 20 minutes showed a significant increase in hardness,adhesiveness,and chewiness during storage.The 20-minute US treatment inhibited the activities of pectin-degrading enzymes polygalacturonase(PG),pectin lyase(PL),and pectin methylesterase(PME)during kiwifruit storage,thereby restraining the conversion of chelate-soluble pectin(CSP)and sodium carbonate-soluble pectin(NSP)to water-soluble pectin(WSP)and increasing the molecular weight of pectin.Monosaccharide composition of pectin indicated that the 20 minutes US treatment delayed the decrease in the linearity and side chain length of kiwifruit pectin.After 12 days of storage,the hardness of kiwifruit treated with ultrasound for 20 minutes increased by 61.11％.Correlation analysis revealed a negative relationship between kiwifruit hardness and WSP content,as well as the activities of PG,PL,and PME(r＞0.85),and a positive relationship with CSP content and molecular weight(r＞0.90).Ultrasound treatment could slow down the softening rate of kiwifruit by regulating the metabolism of cell wall substances.The research findings provide a theoretical basis for extending the shelf life of kiwifruit.
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