Pear Fruit Storage and Fresh-Keeping Methods and Technical Key Points

Different pear varieties and types require different optimal temperature, humidity and optimal gas composition standards. For newly bred varieties, experiments must be conducted to determine the suitable temperature, humidity and optimal gas composition required for their storage, so that temperature and humidity control and gas composition regulation can be effectively carried out during storage to achieve the best storage results. Pear fruits are broadly divided into two major types.

1. Crisp-fleshed type varieties: The white pear system and the sand pear system mostly belong to the crisp-fleshed type. Generally, crisp-fleshed varieties, after harvest, mostly undergo a gradual pre-cooling process at 10°C before entering storage at 0-1°C for fresh-keeping. Taking the new variety Jinfeng pear as an example: pre-cooling is required before cold storage; the pre-cooling temperature should preferably be 5-8°C, and the pre-cooling time should be 1-2 days. If natural low-temperature storage is used, pre-cool overnight at low temperature before loading, and load early the next morning. The suitable storage temperature is 0-1°C; after loading, all means should be used to bring down the storage temperature. The cold storage should reduce the temperature to 0°C within 7-10 days; natural cold storage should reduce it to 0°C within 30-40 days, and no longer than 50 days. The storage temperature must not be lower than -1°C, otherwise chilling injury will occur, causing irregular brown spots in the flesh. Generally, the relative humidity in the storage should be maintained at 85%-90%; for cold storage, the relative humidity should be maintained at 90%-95%. When the humidity in the storage is below 80%, the peel is prone to shriveling. When the humidity in a natural cold storage is insufficient, water should be sprinkled on the floor (a humidifying device can be added in cold storage). For controlled atmosphere storage of Jinfeng pear at 0-1°C, oxygen should be maintained at 10%-15% and carbon dioxide at 1%-2%. Jinfeng pear is very sensitive to low oxygen and high carbon dioxide during long-term storage; under low temperature of 0°C, carbon dioxide reaching above 2% will cause carbon dioxide poisoning injury. Oxygen must not be lower than 10%; too low will also cause injury. Jinfeng pear is a storage-tolerant variety and can be stored for 8-9 months at 0-1°C after harvest.

2. Soft-fleshed type: This type includes varieties of the European pear system and the Qiuzi pear system; after harvest they tend to soften very easily and lose storage value, so after harvest they must be pre-cooled and then immediately placed at a temperature of about 0°C for storage. Taking the Nanguo pear group as an example (including red Nanguo pear and large Nanguo pear), the Nanguo pear group belongs to soft-fleshed type fruit and has a distinct respiratory climacteric period. After the respiration peak arrives, the fruit begins to senesce and the flesh begins to soften. Inhibiting and delaying the arrival of the fruit's respiration peak is an important technical measure for good storage of Nanguo pear. Nanguo pear is harvested at nine-tenths maturity, when the fruit's respiration peak has not yet arrived, but the seed coat has turned dark brown. Pre-cool the harvested Nanguo pears at 5-7°C for 2-3 days, then place them in 0°C cold storage, where they can be stored for 3-4 months. After ripening, they can still maintain their original color, aroma and flavor.

If Nanguo pear is subjected to controlled atmosphere storage, it should first be treated at 15°C for 3-5 days, then transferred to 0°C controlled atmosphere storage, with oxygen concentration maintained at 2%-3% and carbon dioxide concentration maintained at 3%-5%; after storage, it is ripened, and the storage period is 5-6 months. The fresh-keeping effect of controlled atmosphere storage is better than ordinary cold storage. If simple controlled atmosphere storage is adopted, when the flesh of Nanguo pear has not yet softened or is softening, put it into PE bags 0.04-0.05 mm thick and place them in a naturally ventilated storage; the storage temperature should initially be about 15°C and gradually drop to 0°C over 10-20 days. When stored in PE bags, the amount of fruit loaded per bag should not exceed 10 kg. The gas composition in the bag changes somewhat. When the temperature is relatively high at the initial storage stage, oxygen is 2%-3% and carbon dioxide concentration is 5%-8%. When the storage temperature drops to 0°C, the oxygen in the bag rises to 5%-10% and carbon dioxide drops to 3%-5%. Take care to maintain a stable temperature; it can be stored for 3-4 months.