The effects of modified atmosphere and l-methylcyclopropene (1-MCP) treatments on the quality of 'Starkrimson' and 'Granny Smith' apple cultivars stored in the ambient conditions

The study was carried out between 2016 and 2017 at Postharvest Physiology Laboratory of the Department of Horticulture, Akdeniz University and in the ordinary uncooled storage unit in Akçay, Elmalı district of Antalya province. In the research, the effects of 1-methylcyclopropene (1-MCP) and modified atmosphere (MA) treatments and their combination on the postharvest quality of 'Granny Smith' and 'Starkrimson' apple cultivars under cold and ambient storage conditions were investigated. For this purpose, 625 ppb 1-MCP was applied to the fruits that harvested at the optimal harvest stage in the both storage conditions. 1-MCP treatments were carried out at 18 ºC in Elmalı and at 5 ºC in Akdeniz University. 1-MCP were carried out for 24 hours in both storage conditions. After 1-MCP treatments the apples were stored in MA. The control group of fruits were stored without any treatment. Cold storage studies were carried out at 0 ºC temperature with 85-90% relative humidity in cold storage unit of Department of Horticulture, Akdeniz University and the ordinary storage studies were conducted at ambient temperature in Elmalı, Antalya. The temperature and relative humidity of the storage room in Elmalı were monitored by a thermohygrograph. Fruit samples were removed from different storage conditions at 30 day intervals and following parameters; flesh firmness, weight loss, titratable acidity, total soluble solids, skin colour changes (L*, C*, h°), ethylene production, respiration rate, antioxidant activity, total phenolics and total flavonoid contents were examined. At the end of the study, it was determined in both storage conditions that the weight loss and total soluble solids content of the fruits were increased while titratable acidity was decreased. The lowest weight loss was obtained at 1-MCP+MA combination in both storage conditions. The most suitable treatment for titratable acidity was 1-MCP in cold storage and 1-MCP+MA combination in ambient storage conditions, respectively. In addition, 1-MCP+MA combination effectively maintained fruit color by delaying color changes from green to yellow at ambient storage condition for 'Granny Smith' apples. Maintaining fruit firmness at ambient storage conditions, 1-MCP treatment was more efficient for 'Granny Smith' and 1-MCP and 1-MCP+MA were found to be more efficient for 'Starkrimson'. At cold storage conditions, on the other hand, 1-MCP and 1-MCP+MA combination were found to be more successful in maintaining the flesh firmness. 1-MCP treatment controlled the development of P. expansum, the most common decay cause in apples. 1-MCP treatment was also reduced ethylene production, respiration rate, development and severity of superficial scald. It has been determined that apples stored at ambient storage conditions had higher ethylene production and respiration rate. There was no difference among treatments in terms of antioxidant activity and total phenol contents. But, while the total phenolic decreased at ambient storage conditions, no significant changes observed on fruits kept in cold storage. Furthermore, there was no significant effect of storage conditions on antioxidant activity. The total flavonoid content of the apples increased during storage and 1-MCP treatment was further accelerate this increase. In conclusion, 'Granny Smith' and 'Starkrimson' apples stored in cold storage can be stored up to 210 days. But under uncontrolled ambient conditions, storage length without losing market quality were 60 days for 'Starkrimson' and 120 days for 'Granny Smith' apples.