高湿度贮藏环境保持香梨表皮蜡质延缓衰老进程

为了探讨相对湿度对库尔勒香梨表皮蜡质的影响及与耐贮性的关系，该文设置3个不同相对湿度（25 ℃，40%～45%、60%～65%和80%～85%），研究不同湿度贮藏下香梨表皮蜡质含量和化学组分的变化及与贮藏品质的相关性。通过气相色谱-质谱联用技术（gas chromatography-mass spectrometer, GC-MS）对不同湿度贮藏香梨表皮蜡质的化学组分进行比较分析，同时测定好果率、失重率、表观色泽、硬度、可溶性固形物含量、可滴定酸含量、乙烯释放速率和呼吸强度等贮藏品质参数，最后对蜡质含量、化学组分及贮藏参数做相关性分析。结果表明：对照组（相对湿度40%～45%）和处理组的蜡质均由烷烃、烯烃、脂肪酸、醇类、醛类、酯类和萜类组成，但所含具体物质种类和含量略有差异。不同湿度贮藏条件对蜡质含量和各化学组分均有影响，与对照组相比，相对湿度80%～85%贮藏可显著保持蜡质含量、烷烃和醛类物质，延缓脂肪酸和醇类物质增加（P<0.05）。蜡质化学组分及采后衰老之间存在密切相关性，各蜡质组分中，酯类和萜类物质对贮藏品质影响最大，其次是烷烃和醇类物质，其中：酯类物质与失重率、硬度和好果率极显著相关（P<0.01）；萜类物质与失重率和好果率极显著相关（P<0.01）；烷烃物质与失重率极显著相关（P<0.01）。总体来看，在贮藏过程中，高湿度贮藏环境通过保持表皮蜡质含量和化学组分延缓香梨衰老进程，维持稳定的蜡质化学组成对采后香梨贮藏品质的保持具有正向作用。

Delaying the aging process of pears by maintaining cuticular waxes under high humidity storage conditions

Cuticular wax is an important factor that affects storage quality and commercial value of fruits and vegetables after postharvest. Previous studies have shown that cuticular wax of pears undergoes significant changes during storage. However, there are few studies on the effects of different humidity environments storage on the wax changes and the correlation with storage quality. In this paper, the total wax content, chemical composition and the relationship between the wax and storage quality of Korla pear stored at different relative humidity (40% - 45%, 60% - 65%, 80% - 85%) were determined. After extracting cuticular wax by chloroform extraction, chemical compositions were determined by gas chromatography-mass spectrometry (GC-MS). Eight quality parameters (e.g. qualified fruits percentage, weight loss, apparent colour, hardness, soluble solids content, titratable acidity content, ethylene evolution rate and respiratory intensity) were measured and correlation analysis were performed between total wax content, chemical compositions and storage parameters. The results showed that the compositions of fruit wax under different humidity environments were quite similar, mainly including alkanes, olefins, fatty acids, aldehydes, alcohols and esters. Nevertheless, the amount and type of each composition varied. The substances of the primary components with higher contents were nonacosane, hentriacontane, (9Z)-9-tricosene, palmitic acid, oleic acid, docosanol, 1,1-dimethoxydodecane and lanosterin. At the end of storage, the highest cuticular wax content was observed in 80%-85% relative humidity storage and the lowest in 40%-45% relative humidity storage. Compared with the control, high humidity environment delayed the aging process of pear, reduced the decrease of weight loss, hardness, soluble solids content, titratable acid content, and qualified fruits percentage, postponed the peak of respiratory and ethylene release, the 80%-85% treatment was remarkable. Different humidity environment had certain influence on wax content and chemical composition of postharvest pear. The relative humidity of 80%-85% could better maintain the total wax content, alkane and aldehydes, and delay the increase rate of fatty acids and alcohols. Among the components, esters and terpenoids have the greatest influence on storage parameters, followed by alkanes and alcohols. The results showed that the chemical composition of cuticular wax were changed under different humidity environments during storage, at the same time, there was significant correlation(P<0.01) between total wax content, chemical composition and postharvest senescence. In summary, most of the aging process were delayed due to the total wax content and chemical composition were maintained in high humidity environment, manifesting that stable chemical composition of cuticular wax play an important role in keeping good quality of postharvest pear. Overall, to understand the changes of cuticular wax in different humidity environment could provide sufficient information for further study on the effect of cuticular wax on postharvest storage performance. In this paper, the effect of storage in different humidity on the cuticular wax of Korla pear was studied. The change of cuticular wax during shelf life period of pear fruits after storage and control measures to regulate cuticular wax compositions need to be further explored. In addition, the molecular mechanism between cuticular wax chemical compositions and storage quality of Korla pear is not clear, which needs further study.