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.