Abstract To determine whether ozone can regulate fruit ripening and delay fruit aging, Kiwifruit (Actinidia deliciosa 'Guichang') was fumigated with different ozone concentrations (100 μL/L, 200 μL/L, 300 μL/L) for 3 h, stored at 1 °C and 85 ± 5% RH for three months, and then matured at 20 °C and 85% RH for 12 days. Compared with controls, the optimal concentration of ozone delayed kiwifruit ripening during cold storage by delaying the respiratory burst that precedes fruit decay. Consequently, fruit firmness, nutrient content, and enzyme activity remained stable; the expression of AdACS1 and AdACO1 as well as the activity of ACC synthetase (ACS) and ACC oxidase (ACO) was downregulated, whereby ACC and MACC were accumulated. In addition, ozone-treated fruit showed significantly reduced infection with grey mold. The effect of ozone on kiwifruit at 200 μL/L was the best suited for delaying fruit senescence, maintaining high quality during storage and fruit ripening compared with other fruits. Overall, our study indicated that ozone may play a major residual role in the physiological process of fruit ripening; furthermore, ozone can affect ethylene biosynthesis and fruit changes associated with endogenous ethylene production.

Abstract We investigated the effects of melatonin (MT) treatment on the physiological quality and cell wall metabolism of kiwifruit during a 12-day shelf life period (20 ± 1 °C, 90 ± 5% RH), after 90 days of cold storage (0 ± 0.5 °C, 90 ± 5% RH). Our results showed that MT treatment delayed kiwifruit softening, as evidence by the enhanced endurance of a healthy appearance, quality, color difference L* value, and firmness of the fruit flesh. MT treatment reduced fruit decay rate, respiration rate, and malondialdehyde content; furthermore, MT-treated kiwifruit maintained high levels of total soluble solids, titratable acid, and ascorbic acid. Additionally, MT inhibited the decrease in fruit pectin, cellulose, and hemicellulose contents; it delayed the increase in water-soluble pectin content and kept pectin methyl esterase, polygalacturonase, cellulase, and β-galactosidase activities low. These results indicated that melatonin may have reduced the speed of softening of kiwifruit and preserved fruit quality by inhibiting enzymatic degradation of the cell wall, and by delaying pro-pectin, cellulose, and hemicellulose degradation, as well as the increase of water-soluble pectin content. These findings indicate that MT treatment may be an effective measure to delay kiwifruit postharvest cell-wall metabolism and preserve fruit quality.

Abstract The effects of 1-methylcyclopropene (1-MCP) treatment and controlled-atmosphere (CA) storage and their combination on quality and antioxidant capacity of postharvest blueberries were evaluated here. To investigate the most appropriate approach for maintaining fruit quality, blueberries were subjected to four different treatments, a control (CK), 1-MCP, 3% O2 + 10% CO2 (CA), and 1-MCP combined with 3% O2+10% CO2 (1-MCP + CA), then stored for 80 days at 0 °C. It was found that the applications of 1-MCP, CA and 1-MCP + CA were effective at delaying the increase in weight loss and inhibiting the decrease in firmness, total soluble solids (TSS) contents and titratable acidity (TA) contents. In addition, 1-MCP, CA and 1-MCP + CA treatment could significantly suppress MDA accumulation and relative electrolytic leakage promotion. Moreover, the production of reactive oxygen species (ROS), such as O2- and H2O2, was reduced by all the treatment, which was associated with increased activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Taken together, our findings indicate 1-MCP, CA and 1-MCP + CA have potential applications in maintaining the quality and improving the antioxidant capacity of harvested blueberries, and 1-MCP + CA is the most effective treatment.

Abstract Pitaya fruits have high senescence rates throughout their postharvest storage period. Additionally, studies have confirmed that melatonin plays a regulatory role in plant senescence. However, the involvement of melatonin in the postharvest senescence of fruits remains unclear. In this study, two cultivars of pitaya fruit, ‘Zihonglong’ and ‘Jinghonglong’, were treated with melatonin and then evaluated for characteristics of senescence while in storage for 10 days. The results showed that melatonin treatment delayed fruit senescence in both pitaya cultivars, as indicated by the inhibition of weight loss, decay incidence, relative membrane permeability, and malondialdehyde (MDA) content, as well as the maintenance of the total soluble solids and ascorbic acid contents and the reduced respiration intensity. In addition, melatonin treatment reduced the O2·- production rates, H2O2 contents, and lipoxygenase activities but enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in both pitaya cultivars. These results indicate that melatonin may contribute to delaying senescence in pitaya fruits. This study shows the potential of the use of melatonin in the postharvest storage of pitaya fruits, as well as other horticultural fruits.

Abstract Melatonin is known to influence various physiological processes, including plant ripening; however, the effect of melatonin on postharvest blueberry fruit softening is unknown. Herein, the effects of melatonin at different concentrations (100, 300, and 500 μmol L-1) on the quality parameters, cell wall substances, cell-wall-degrading enzymes, and cell wall ultrastructure of blueberry fruits were investigated during low-temperature storage. Melatonin treatment was found to effectively delay the decline in fruit firmness, slow the loss of soluble solids and titratable acids, and decrease the respiration rate and decay rate of blueberry fruits. The blueberry fruits treated with 300 μmol L-1 melatonin exhibited the best quality. Melatonin treatment promoted anthocyanin accumulation, delayed ascorbic acid degradation, maintained a low relative membrane permeability in pulp, inhibited increases in lipoxygenase (LOX) activity, and reduced membrane lipid peroxidation. Moreover, melatonin controlled the formation of soluble pectin by inhibiting the activities of pectin methylesterase (PME), polygalacturonase (PG), cellulase (Cx), and β-glucosidase (β-Glu) while maintaining high contents of protopectin and cellulose. These results indicate that melatonin can effectively improve blueberry fruit quality and antioxidant capacity as well as and delay fruit softening by inhibiting the degradation of cell wall substances.

Abstract In this work, the effects of 1-methylcyclopropene (1-MCP) on texture properties, titratable acidity (TA) and total soluble solids (TSS) in blueberry were examined during long term storage and simulated transportation. Blueberry fruits were stored at 0 ± 0.5 °C after being treated with 0.1, 0.2 and 0.3μL L-11-MCP. After 40 and 80 days of storage, quickly put 8 punnets into a foam box with commercial cold pack to simulate the commercial transportation for 2 days at 25 °C. There were considerable differences in the texture properties during long term storage and simulated transportation with 1-MCP. The 0.3 μL L-1 1-MCP can effectively decreased the decline of gumminess and chewiness, retarded the reduction of TA, and delayed blueberry fruit softening. There was significant positive correlation among firmness, springiness, cohesiveness, gumminess, chewiness, resilience, TSS, and TA. These results demonstrate that the 0.3 μL L-1 1-MCP combines with commercial polyethylene bags were successful effect in maintaining the texture properties of blueberry.