采后黄金百香果失水规律及其与品质劣变的关系

采后失水是百香果果实在贮运流通和销售环节最显著的品质劣变特征之一，严重影响其商品价值。本文利用低场核磁共振技术（Low Field Nuclear Magnetic Resonance，LF-NMR）研究采后黄金百香果果实在贮藏过程中的失水过程，并解析失水规律与品质劣变的关系。LF-NMR结果显示，黄金百香果在贮藏过程中，果浆和果皮的质子密度大幅下降，与外观严重失水表现一致；此外，果实失水以自由水为主，其含量下降了14.98%，结合水在贮藏后期显著减少，失水程度与果实采后成熟和衰老进程有关。进一步研究表明，黄金百香果采后成熟期有两个呼吸高峰，此时失水及其引起的失重较小，果皮叶绿素减少和类胡萝卜素增加促进了亮度和色调升高，果浆可溶性固形物保持在较高含量，可滴定酸含量和果实硬度均下降，果实正常完成后熟，极少出现腐烂；而在果实衰老期，呼吸速率下降，失水和失重加剧，果皮类胡萝卜素的迅速减少降低了表面亮度和色泽，果浆可溶性固形物和可滴定酸含量以及果实硬度下降，腐烂率迅速升高。因此认为，黄金百香果完熟后严重失水，不仅造成果实失重、失鲜，还可加剧其生理代谢以及细胞和组织结构变化，降低果实耐贮性，加快品质劣变。本研究可为百香果采后失水劣变机制和相应保鲜控制技术研究提供参考，并为果蔬采后水分状态的无损检测提供借鉴。

Postharvest Water Loss Pattern of Golden Passion Fruit and Its Relationship with Quality Deterioration

Water loss is one of the most significant quality deterioration characteristics of passion fruit during postharvest storage, transportation and marketing, which seriously affects its commercial value. In this study, Low Field Nuclear Magnetic Resonance (LF-NMR) was employed to investigate the water loss process of golden passion fruit during storage, and the relationship between water loss and quality deterioration was analyzed. The results of LF-NMR showed that the proton density of the pulp and peel of golden passion fruit decreased significantly during storage, which was consistent with the appearance after severe water loss; additionally, the water loss of fruit was mainly free water with 14.98% decrease, while the bound water decreased significantly in the later stage of storage; and the degree of water loss was related to the process of postharvest ripening and senescence. Further studies showed that there were two respiratory peaks during postharvest ripening period of golden passion fruit, meanwhile the water and weight loss was low, and the decreased chlorophyll content and increased carotenoid content contributed to higher brightness and hue; moreover, the total soluble solids (TSS) content decreased slightly, but titratable acid (TA) and fruit firmness decreased remarkably, indicating a normal postharvest ripening of fruit with rare rot. However, in the senescence period, the respiration rate declined as the water and weight loss increased, and the brightness and hue decreased as the carotenoid reduced rapidly; Furthermore, the TSS and TA contents, and fruit firmness kept decreasing, along with a rapid increase of decay rate. Therefore, the severe water loss of golden passion fruit could not only cause significant loss of weight and freshness, but also induce changes in physiological metabolism, cellular and tissular structure, which reduced fruit storage tolerance and accelerated quality deterioration. This study can provide reference for the study on the mechanism of water loss and corresponding control technology of passion fruit, as well as the non-destructive testing of water status in postharvest fruit and vegetables.