Effect of Bagging on Wax Components and Storage Quality of ‘Yali’ Pear

In order to explore the effect of bagging on the wax compositions and storage quality of ‘Yali’ pear fruit, the differences and correlations of wax content and distribution, nutrition and quality indicators, and antioxidant properties of the two different treatments (polyethylene, (PE) plastic film bags and three-layer paper bags) stored at 25 ℃±1 ℃ were analyzed. The fruits were bagged at day 60 after blooming, then the bags were removed at harvest, and no-bagged fruit acted as the control. The results showed that the highest rate of fruit weight loss was found in PE plastic film bags-treated fruit, while there was no difference in fruit hardness, brittleness and compactness between the control and the two treatments within 14 days of storage. The increases in contents of wax compositions alkenes, fatty aldehydes, fatty alcohols, esters, and total wax were significantly delayed in the two treatments. The contents of alkanes C₂₇ and C₂₉, alkenes C₂₄-C₂₆, fatty acid C_18:1, fatty aldehydes C₂₆ and C₃₄, even number fatty alcohols C₂₂-C₂₈, seven esters, and triterpenoids (such as α-farnesene, β-amyrin, lupeol, and β-amyrenone) in the two treatments were lower than the control. In addition, compared to the PE plastic film bags treatment, the decline in contents of wax compositions alkene C₂₆, fatty acids C₁₆ and C_18:1, even number fatty aldehydes C₂₈-C₃₂, two esters (C_22:1 alcohol-C_18:1 acid and C_24:1 alcohol-C_18:1 acid), triterpenoids (Urs-12-en-28-al,3-(acetyloxy)-,(3á)-and Urs-12-en-28-al) were delayed by the three-layer paper bags treatment. Furthermore, in comparison with PE plastic film bags treatment, higher contents of peel flavonoids, peel total phenols (at day 14), fruit titratable acid and Vc (at day 14), and higher DPPH clearance rate were found in three-layer paper bags-treated fruit. According to PCA analysis of wax components, the control and the three-layer paper bags treatment were belonged to one group, while PE plastic film bags treatment was divided into the other group. The correlation analysis showed that wax components alkanes, fatty aldehydes, triterpenes and total wax in different treatments were positively correlated with the content of peel flavonoids (P<0.05), while fatty alcohols, esters and total wax were positively correlated with the content of fruit V_C (P<0.05 or P<0.01). This study indicated that the three-layer paper bags treatment could delay the decline in accumulation of some fruit wax components, maintain the higher peel antioxidant capacity, and thus enhance fruit quality of ‘Yali’ pear.