不同预冷降温速度对减轻桃果实采后机械伤的影响

Effects of Different Temperature Changing Rates during Precooling on Reducing Mechanical Damage of Peach Fruit after Harvest

桃果实营养丰富,易于消化吸收,深受消费者喜爱。但桃果实采后易遭受机械伤,导致腐烂损耗,严重影响商品价值。本实验以‘湖景蜜露’桃为材料,并对其进行不同降温速度的预冷处理(果心温度在3 h或16 h内从27℃降至9℃),以不进行预冷处理的材料为对照(Control check,CK),然后再对桃果实进行挤压机械伤处理(通过质构仪模拟挤压处理,探头直径100 mm,测试深度10 mm,挤压速度1.5 mm/s),以研究不同预冷降温速度对减轻桃果实采后贮藏物流过程中遭受机械伤的影响。结果表明,对桃果实进行预冷处理,尤其是3 h快速预冷处理,可以降低果实瘀伤指数、腐烂率和失重率,延缓果实硬度下降,并且还会加速苯丙氨酸裂解酶活性在贮藏后期的上升。其中经过3 h的快速预冷处理,果实瘀伤指数和腐烂率相较CK分别降低了11.7%和8.3%。预冷处理还可抑制桃果实因遭受机械伤而导致的呼吸速率、乙烯释放量、丙二醛含量和多酚氧化酶活性的上升,其中3 h快速预冷处理和16 h慢速预冷处理在贮藏21 d时的多酚氧化酶活性分别为CK的75.7%和72.1%。此外,预冷处理也会延迟总酚含量的上升,两个预冷处理组在贮藏7 d时总酚含量分别为CK的85.1%和92.1%。综上,对采后桃果实提前进行快速预冷处理有利于减轻果实在后续因遭受挤压机械伤所导致的品质劣变和腐烂损耗,提高果实商品性。

Peach fruit is rich in nutrition,easy to digest and absorb,and loved by consumers.However,peach fruits are prone to mechanical damage after harvesting,decay and quality loss,limiting their commercial value.This study investigated the effect of different precooling rates on the reduction of mechanical damage in peaches after harvest.'Hujingmilu'peach fruits were subjected to precooling treatments(rapid precooling for 3 h and slow precooling for 16 h,reducing the core temperature of the fruit from 27℃to 9℃),with the control(Control check,CK)being without precooling.Afterwards,the fruits were subjected to compression damage(A texture analyzer with a probe diameter of 100 mm,a test depth of 10 mm and an extrusion speed of 1.5 mm/s was used to simulate the compression process).Overall,the precooling treatment,especially the rapid precooling treatment of 3 h,reduced bruise index,decay rate and weight loss rate,delayed the decline of fruit firmness during storage and accelerated the rise of phenylalanine ammonia lyase activity in the late storage period.In particular,the bruise index and decay rate of the fruits subjected to rapid precooling(3 h)were reduced by 11.7%and 8.3%,respectively,compared to the control treatment.Furthermore,the precooling treatments,regardless of time(3 h or 16 h),minimised increase in respiration rate,ethylene production,malondialdehyde content and polyphenol oxidase activity in the peach fruit with compression damage.The polyphenol oxidase activities in rapid precooled and the slow precooled fruits were 75.7%and 72.1%,respectively of the control at 21 d of storage.In addition,the precooling treatments also delayed the increase in total phenolic content,with rapid and slow precooling having 85.1%and 92.1%,respectively of phenolic content contained in the control treatment at 7 d of storage.In conclusion,rapid precooling of postharvest peach fruit prior to compression damage can reduce quality deterioration and decay of the peach fruit,and therefore,could improve the marketability of the fruit.