Effects of harvest date combined with 1-MCP on postharvest physiological and storage quality of 'Venus Gold' apple

Abstract: 'Venus Gold' apple (known as 'Weihaijin') is a new variety of large fruit, late maturing, and fine apples by the Iwate University of Japan from the natural hybrid offspring. The 'Venus Gold' apple at its best maturity is favored by the market, due to its golden and crisp flesh, richness in juice and fresh fragrance, unique taste, and excellent quality. However, there is no accurate reference to determine the optimum harvest period or maturity of 'Venus Gold' apples at present. This study aims to clarify the influence of the 1-Methylcyclopropene (1-MCP) treatment on the postharvest physiology and storage quality of 'Venus Gold' apples at different harvest periods. A reliable theoretical basis and technical support were provided for the harvest standard of the 'Venus Gold' apples in the production, the quality improvement, as well as the delay of softening and aging in the postharvest storage. In this experiment, three harvest periods were selected as the growth and development period of 185 days (harvest period I), 192 days (harvest period II), and 199 days (harvest period III). The concentration values were also set as 0 (CK), and 1.0 μL/L 1-MCP after treatment. The postharvest physiology and storage quality were evaluated at room temperature (20±0.5)℃ at a relative humidity of 85%-90%. The results showed that there were higher and earlier peaks of respiration and ethylene in the late-harvested fruits, compared with the CK. The 1-MCP treatment significantly reduced the ethylene release rate and respiration intensity of fruits in the three harvest periods, and then significantly inhibited or delayed the occurrence of respiration and ethylene climacteric peak. There was no significant difference in the starch content and amylase activity between the 1-MCP treatment and CK in the fruits at the harvest stage I and III (P≥0.05). However, the 1-MCP treatment greatly contributed to the higher hardness and original pectin content of fruits at the harvest stage I and III, indicating the delay of the soluble pectin content and PG activity. There was a significantly (P<0.05) inhibited effect on the increase of amylase activity during the storage period of 13 to 25 days, indicating the effective delay of starch conversion. Harvest period II presented better quality of the soluble solids, titratable acid, and vitamin C of 'Venus Gold' apple, compared with harvest period I. By contrast, harvest period II significantly delayed the fruit softening and aging for the longer shelf life, indicating the higher fruit hardness and titratable acid content, compared with harvest period III. An optimal combination was achieved in the storage and freshness preservation after comprehensive analysis: the growth and development period of 'Venus Gold' apples was harvested in 192 days combined with the 1.0 μL/L 1-MCP treatment during 25 days of normal temperature storage.