"1-MCP" preservative can effectively control various physiological and biochemical reactions of postharvest kiwifruit, including the release of ethylene and respiratory intensity, etc., inhibit the ripening effect of endogenous ethylene and exogenous ethylene on kiwifruit, and slow down the aging process of kiwifruit , prolong the storage period of kiwifruit, maintain fruit hardness and nutrients, and prevent fruit from softening and rotting.
1. Physiological characteristics and storage characteristics of kiwifruit
Kiwifruit is a climacteric fruit with a physiological post-ripening period and is very sensitive to temperature and ethylene. If it is not processed in time after harvesting, the ethylene in the fruit will increase rapidly at room temperature, and the respiration will be significantly enhanced. After reaching the peak, the starch content will decrease, the pulp will become soft, and the sugar content will increase, which will lead to aging and rot.
So far, there are more than 100 varieties and varieties of Actinidia plants, and the most economically valuable ones are Chinese Actinidia and Delicious Actinidia. Generally speaking, gourmet kiwi is more durable than Chinese kiwi. For the same species, the storability of different varieties (strains) is also quite different. Generally, early-maturing varieties have poor storability, while "Hayward", "Qinmei", "Luoyang No. 1", "E-30", "Huaguang No. 5", "Tongshan No. The storability of varieties such as "Haohao" is better; the size of the fruit also has a certain relationship with the storability. Generally speaking, the fruit is small and the specific surface area is large, so the transpiration of water is stronger and the weight loss is faster. The fruit treated with over-expansion agent has poor storability and cannot be used for medium or long-term storage.
2. Harvesting and Precautions
2.1 Harvesting period:
The maturity of the harvest has an important impact on the quality and storability of the fruit. If the harvest is too early, the fruit will not be fully developed, the quality will be poor, and it will not tolerate storage; if the harvest is too late, the fruit will be fully mature. The quality and flavor are good, but the fruit is easy to soften and not resistant to storage. In order to ensure the best storage period and fruit quality, Chinese kiwifruit is better harvested when the fruit soluble solid content is 6.2% to 6.5%, and delicious kiwifruit is better harvested when the fruit soluble solid content is 6.5% to 7%. This kind of fruit is not only resistant to storage, but also has the best flavor after storage.
2.2 Precautions:
The key to harvesting kiwi fruit is to avoid all mechanical damage as much as possible. Generally, manual harvesting is adopted and carried out in batches according to maturity. Fruit pickers should cut their fingernails short, and it is best to wear gloves to harvest; do not irrigate the garden within 5 days before harvesting, and do not apply nitrogen fertilizers within 20 days. Harvesting should be carried out in the morning on a sunny day or when the morning fog has disappeared. It is not suitable to harvest within the next 6 days and in the morning when the dew is not dry. The whole operation process should be handled with care, put down, loaded and unloaded with care to avoid bruising and stacking. The harvested fruits should be placed in a shaded place.
3. Preparation before warehousing
3.1 Pre-cooling Kiwi fruit should be pre-cooled before low-temperature storage, otherwise the storage property will be seriously affected. When harvested, kiwifruit often maintains a relatively high "field heat", and physiological activities such as respiration and metabolism are vigorous, and it is easy to spontaneously ripen. At the same time, if it is directly sent to the cold storage without pre-cooling, the temperature difference of about 20°C inside and outside will cause physiological activity disorder and excessive freezing injury of the fruit, and water will condense on the fruit surface, increasing the chance of pathogen invasion. The fruit should be pre-cooled to 5°C as soon as possible after harvesting, and the delay time at room temperature should not exceed 8-12 hours.
3.2 Warehouse management Eliminate peculiar smells and sundries in the warehouse. Wash the ground with saturated potassium permanganate solution or bleaching powder, then close the warehouse door for 24 hours, or fumigate with 5-15 grams of sulfur mixed with dry sawdust per cubic meter for 48 hours, and then turn on the machine to cool down. Reduce the temperature of the sterilized cold storage to 0°C two days in advance, and then put the pre-cooled fruits into the storage. The storage temperature should be stable at about 2°C. After all the storage is completed, adjust the temperature inside the storage. In addition, try to fill the warehouse within a week or so, and keep it fresh in time.
4. "1-MCP" preservation treatment
Ethylene has a great influence on the storability of kiwi fruit. Under the condition of 0℃, even a small amount of ethylene (30ppb) will obviously accelerate the progress of post-ripening decay, soften the flesh and shorten the storage life. Therefore, it is very necessary to treat with "1-MCP" preservative and store under low temperature conditions.
After the storage is full, the "1-MCP" preservative should be used for fumigation in time to inhibit the release of ethylene and reduce the breathing intensity. For long-term storage, secondary fumigation can be carried out if necessary.
5. Storage management:
5.1 Suitable storage conditions:
Temperature: -0.5℃～0.5℃
Humidity: 90%～95%
Controlled atmosphere conditions: O2: 2%~3% CO2: 4%~5% C2H4<0.02 μl/L
The storage of kiwifruit requires stable temperature and humidity, and frequent changes in temperature and humidity are extremely harmful to the storage of kiwifruit. The optimum relative humidity for refrigeration should be controlled at 90% to 95%. Less than 90% of the fruit is prone to water loss and wrinkled skin, and more than 95% of the pathogenic bacteria are easy to invade. The storage temperature should not be lower than -1.5°C to avoid freezing damage and loss of commodity value.
In the early stage of storage, the temperature in the warehouse can be kept at about 0°C, and in the later stage, it can be appropriately lowered with the decrease of the external temperature, and can be adjusted down by 0.1°C every week or so. In the early stage, because kiwifruit contains a lot of water, the humidity in the warehouse should be properly controlled to prevent the growth of mold. In the later stage, the warehouse is dry and can be properly watered.
5.2 Sterilization: During storage, it should be sterilized regularly, preferably every half a month, and the effect of using fungicides in rotation is better.
5.3 Ventilation: Change the air every 25 days or so, and the ventilation time is controlled at about half an hour. Choose sunny days when the outside temperature is low.
5.4 Out of the warehouse and on the market: The kiwi fruit that has been fumigated with "1-MCP" preservative has a long shelf life after being out of the warehouse, so the temperature can be slowly raised one week before the out of the warehouse according to specific needs. 2-4°C, it can be sold as soon as possible after listing.
6. Storage diseases and their prevention and control:
Stem rot is the main disease that causes fruit rot during kiwifruit storage.
Symptoms: Affected fruits appear obvious water stains at the fruit pedicle at first, and then the lesions spread downwards evenly, feeling soft and elastic, and the other parts are not much different from healthy fruits. When the diseased fruit is cut, the pedicle will rot first, and the rot will spread downward in the pulp, but the top of the fruit will generally remain intact. The rotten pulp is water-soaked, slightly transparent, smells like wine, and slightly discolored. With the development of the disease, a layer of gray-white mold grows out of the diseased fruit, and the mold on the outside of the diseased fruit often spreads to adjacent fruits, causing re-infection.
The pathogens are Botrytis cinerea and Penicillium, and the pathogens and conidia overwinter on the diseased fruit and spread through airflow. The fungus first causes flower rot and leaf rot, and fruit infection mostly occurs during fruit picking and grading packaging.
Prevention methods:
(1) Do a good job in the prevention and control of flower rot in the field to reduce the source of bacteria. And about 20 days before picking the fruit, spray 65% mancozeb 600 times or prothine 1000 times.
(2) Carry out chemical antiseptic treatment in time within 24 hours of fruit picking. It can be sprayed with 20 times solution of Jing-2B film, 20 times solution of Jing-2B film plus 500mg/L carbendazim or thiophanate-methyl.
(3) Low temperature storage. Under refrigerated conditions at 1°C, it takes about 4 weeks for the infected fruit to appear pedicle rot, and the fruit without disease after 40 days of storage, although it may be re-infected, generally does not develop disease.
