Pear is a climacteric fruit with a post-harvest ripening period, and is very sensitive to temperature and ethylene. If not dealt with in time after harvest, the ethylene in the fruit will increase rapidly at room temperature, and respiration will grow significantly. After reaching the peak of respiration, the nutrient content in the fruit will be consumed in large quantities and the moisture will be lost. As a result, the fruit will gradually age and lose its edible value. Therefore, pears need to be kept fresh at low temperatures as soon as possible after being harvested.
The 1-MCP treatment has a good fresh-keeping effect on most pears. After pears are pre-cooled and put into storage, the 1-MCP treatment should be applied in time to extend the storage and shelf life. Cathy, head of Chesen Biochem Co., Ltd., a specialised manufacturer of fresh-keeping agents, introduced this pear fresh-keeping product.
According to Cathy, 1-MCP is able to effectively control various physiological and biochemical reactions of pears after harvest, including lowering the release of ethylene and respiratory intensity, inhibiting the ripening effect of endogenous ethylene and exogenous ethylene, and reducing the activity of polyphenol oxidase, cellulase and peroxidase. This will slow down the ripening and deterioration process, prolong the storage life, and maintain the visual quality, flavour, firmness and nutritional content of the fruit. In addition, it can also prevent various physiological conditions during storage.
It is worth noting that different varieties of fresh pears have different storability. Early varieties are generally not resistant to storage, while mid-and-late varieties are more resistant. "For example, among the Asian varieties, the white pears (Ya pears, Snow pears, etc.) are more resistant to storage; among the European varieties, Williams pears are not resistant to storage at room temperature - generally, they will quickly ripen and deteriorate about 10 days after being harvested.
Different varieties also have different temperature and humidity requirements during storage. In addition, you should also regularly sterilise and ventilate the cold storage. Ventilation should be carried out for about half an hour on a sunny day when the outside temperature is low,” Cathy said. "The sensitivity of different varieties to 1-MCP also varies. Generally speaking, Asian pears can be treated with 1-MCP in a similar way to apples, but European pears are extremely sensitive to 1-MCP, so the concentration of fumigation should be carefully controlled.”
Cathy also shared the storage and 1-MCP treatment tips for two common Asian and European pears:
1. Snow pears
Snow pears are thick in peel and firm in flesh, so they are storage-resistant. The best storage temperature is 0—1℃. When being put into cold-storage, the pears should be kept at 8℃—11℃ in the humidity of around 90%. If the temperature is too low, the pulp tissue will be damaged and deteriorate, while if the temperature is too high, the storage life will be affected. The process of putting the pears into storage needs to be as short as possible; it generally needs to be completed within 10-15 days. After this process is completed, the storage cells should be kept at the original temperature for 3 days.
Afterwards, the temperature needs to be lowered by 1°C every 3 days, stay at 4°C for 3-5 days when it reaches this temperature, and then be lowered by 1°C every 2 days until it drops to 0°C. The cooling period should be completed within 30-35 days. The storage temperature shouldn’t be lower than 0℃, and the humidity in the later period needs to stay at 90-95%. By using the 1-MCP treatment, the products need to be fumigated at a concentration of 0.5~1.0μl l−1 at 0℃ for 12-24 hours.
2. Williams pears
Williams pears are not resistant to storage at room temperature, so they should be put into cold storage in time after being harvested. They can also be stored under controlled atmosphere. They are best kept at a temperature of 0℃, with the O2 content of 2-4%, the CO2 content of 3-4%, and relative humidity of 90-95%. Different from apples and most Asian pears, this variety must be placed at a temperature of 20°C for 3-4 days after they leave storage to ripen and soften before they can be consumed. As the effect of 1-MCP is not easily reversed by exposure to ethylene, it must be treated in a certain way so that the fruit can ripen and soften normally after storage. The rate at which the fruit recovers ethylene sensitivity mainly depends on the concentration of 1-MCP applied.
Chesen BioChem is a specialised 1-MCP research, production and sales company in Hefei, China. The company also offers other agrochemicals. Each year, the company participates in international exhibitions such as Fruit Logistica to meet customers old and new. The company's 1-MCP has not yet been registered in other countries, but it is actively looking for interested distributors to register and promote the product across the world.