Effects of exogenous ethylene treatment on the peel browning and shelf life quality of Huangguan pears

Abstract: Low-temperature refrigeration has been commonly used for post-harvest storage and preservation of fruits. But the long-term low-temperature storage can lead to the browning peel of Huangguan pear, or even be detrimental to the fruit quality. Alternatively, ethylene can serve as an endogenous hormone to regulate plant growth and development, whether fruit ripening or the stress resistance of plants. In this study, the slow release of exogenous ethylene with different concentrations was selected to treat the Huangguan pear fruits before storage, in order to explore the effects on the peel browning and quality during the subsequent shelf life. Three ethylene concentrations were produced in the same volume of closed space: 5, 20, and 100 μL/L. The control group was taken as the Huangguan pears with the rapid cooling at 0 ℃ and without the exogenous ethylene treatment. The low-temperature treatment group was set: the Huangguan pears after harvesting was immediately treated by cooling to 0 ℃, where the temperature was kept at 30 ℃and decreased by 1 ℃ every day for 30 days. Some indicators of fruit quality were then measured, including the water content, disease incidence, soluble solids, soluble sugar, titratable acid, and ascorbic acid. The performance of postharvest exogenous ethylene treatment was evaluated on the fruit quality, in order to avoid the occurrence of browning of the fruit peel under low-temperature storage (about 0℃). The results showed that the different concentrations of exogenous ethylene treatments completely inhibited the occurrence of browning of the peel of Huangguan pear, where there were no signs of damage on the epidermis. The incidence indexes were 10% and 37.6% for the low-temperature condition treatment and the control, respectively. At the end of the shelf life (6 d), the fruit firmness of the exogenous ethylene treatment group was significantly different from that of the control group (P < 0.05). The water content of fruits in the three different concentrations of exogenous ethylene treatment groups were higher than those in the control and low temperature condition treatment (P < 0.05), which maintained the excellent taste of Huangguan pear. A low-field nuclear magnetic resonance (NMR) showed that there was a lower free water content of the 5 and 100 μL/L exogenous ethylene treatment groups, compared with the control. It infers that the low free water content reduced the incidence rate of peel browning. The exogenous ethylene treatment maintained the content of soluble solids in Huangguan pear fruit. Exogenous ethylene treatment improved the fruit quality indicators, such as the titratable acid, soluble sugar, and ascorbic acid in the Huangguan pear fruits, indicating the better sensory quality of pear fruit. Among them, the treatment was performed better at the concentration of 5 μL/L. The exogenous ethylene treatment before storage can serve as an efficient and simple technology to inhibit the browning of Huangguan pear peel for a better shelf-life quality of fruits.