冷藏对南果梨酯类香气合成关键酶活性及蛋白表达的影响

以南果梨为试材,系统分析冷藏及冷藏后常温货架期间南果梨果实酯类香气物质的变化,研究酯类香气物质代谢途径关键酶脂氧合酶(lipoxygenase,LOX)和醇酰基转移酶(alcohol acyltransferase,AAT)活性及蛋白表达水平的变化,探讨冷藏对南果梨酯类香气物质代谢影响的作用机制。结果表明,与冷藏90 d相比,冷藏180 d的南果梨在出库时以及冷藏后转入常温货架期果实后熟至最佳食用期时,果实酯类香气成分种类、主要香气成分与总酯含量均明显减少;冷藏过程中果实LOX和AAT活性与表达量变化不明显,但在冷藏后常温货架期间,冷藏180 d的处理果实LOX和AAT活性以及LOX蛋白表达高峰出现的时间较冷藏90 d的处理果实提早3 d,AAT活性显著低于冷藏90 d的处理,LOX和AAT蛋白表达水平也显著低于冷藏90 d的处理。由此可见,长期冷藏一定程度上抑制了南果梨酯类香气物质合成关键酶活性与蛋白表达,从而影响了果实酯类香气物质的合成,降低了冷藏南果梨的香气品质。

Effect of Cold Storage on the Activities and Protein Expression of Key Enzymes Involved in the Biosynthesis of Aroma-Related Esters in ‘Nanguo’ Pears

In order to explore the mechanism of the effect of low temperature storage on the metabolism of aroma-related esters in ‘Nanguo’ pears, the changes in the composition of aroma-related esters, and the activities and protein expression of lipoxygenase (LOX) and alcohol acyltransferase (AAT), the key enzymes for the metabolism of aroma-related esters, in Nanguo pears during cold storage and subsequent shelf life at ambient temperature were investigated. Results showed that compared with storage for 90 days, the number of aroma-related esters, the content of the major aroma components and total ester content after 180 days of storage and after subsequent ripening at ambient temperature until the optimal consumption date significantly decreased. There was no significant difference in the activities and protein expression of LOX and AAT during cold storage. However, during the shelf life at room temperature after cold storage, the activities and protein expression of LOX and AAT reached the maximum levels three days earlier in the 180-days stored fruits than the 90-day stored ones. Moreover, the former showed a significant reduction in AAT activity and the protein expression levels of LOX and AAT. These results indicated that long-term refrigeration could inhibit the activities and protein expression of the key enzymes for the biosynthesis of aroma-related esters to a certain extent, thus affecting the generation of aroma-related esters and reducing the aroma quality of Nanguo pears.