Study On The Chilling Injury And Quality Regulation Technologies Of Postharvested Papaya Fruit

Papaya(Carica Papaya.L)is a popular tropical fruit with soft texture,sweet and high nutritional value.Papaya belongs to respiration climacteric and cold-sensitive fruit which is easy to ripening and soften and rot seriously during storage time and transportation.In this study,the effects of hypobaric pre-treatment,heat shock treatment and cold shock treatment on postharvest physiologies,storage quality and antioxidant quality of 'Risheng' papaya fruit.In addition,the effects of heat shock and cold shock treatments on fruit chilling injury and the quality of shelf-life were studied.The results were as follows:1.To study the different hypobaric pre-treatment(0 MPa,0.025 MPa,0.05 MPa,0.075 MPa)on storage quality and antioxidant activity of papaya fruit.The results showed that hypobaric pretreatment could significantly delay the decrease in fruit firmness.inhibit the changes in contents of TSS.Vc,flavonoids content,maintain the total phenol content and higher SOD activity,inhibit the accumulation of malondialdehyde(MDA)compared with the control group(C.K).These are advantageous to maintain storage quality and antioxidant capacity of papaya fruit.Anong all treatments,the effect of 0.05 MPa was the most significant,then followed by 0.075 MPa.2.The effects of heat shock treatment(50? and 55? hot water for 10 min)on postharvest physiology and antioxidant activity of papaya fruit stored at 12? and 20,C were studied.The results showed that heat shock treatment could significantly delay the decline in fruit firmness,delay the change of peel color,maintain high TSS content,increased Vc and TA contents,and delay the change of flavonoid content.The peak of SOD was delayed and maintain the activity of SOD at the late stage of storage.Hot water treatment at 50? for lOmin had more significantly effect on prolonging storage about 10 days at low temperature and 5 days at room temperature.3.The effects of cold shock treatment(ice-water treatment for 0.5 h)on postharvest physiology and antioxidant activity of papaya fruit under the condition of cold storage at 15? were studied.The results showed that cold shock treatment could delay the decline in firmness,inhibit the change of fruit color,delay the peak of Vc content,increase the peak of TSS.It could significantly suppress the accumulation of MDA,maintain SOD and POD activities,and delay the content changes of flavonoids and total phenols,which is beneficial to maintain the quality and anti-oxidation of papaya fruits during the storage period.4.To study comparatively the effects of heat shock treatment and cold shock treatment on chilling injury and and shelf life quality of papaya fruits.The results showed that both heat shock treatment and cold shock treatment could significantly reduce chilling injury of papaya fruit under low temperature stress(5?),and slow down the rise in cell membrane permeability,inhibit the accumulation of MDA content,improve the activity of SOD,delay the decrease in flavonoids content.The fruits were stored at 5? for 20 days and then transferred to 25?(shelf life),heat shock treatment and cold shock treatment could delay the quality change,reduce chilling injury,and the fruit could turn softening and yellow normally.Heat shock treatment was better than cold shock treatment,it could maintain the higher flavonoids content and POD activity,and was helpful to maintain the shelf life and quality of papaya fruit.