Preservation and storage of jujube

Make a beautiful woman and nourish your life. For thousands of years, red jujube has been used as a good product for beauty, anti-aging and longevity, and it is also one of the important food sources for people in jujube areas to survive and tide over famine. Red jujube is different from the general dry and fresh fruit, it integrates medicinal, health care, edible and other functions. Jun jujube, as one of the four famous dates in Shanxi, is favored by consumers because of its unique shape, deep red color, thin skin and thick flesh, large stone fruit and crisp sweet taste. According to the determination, every 100g of fresh jujube contains 28.7g sugar, 0.45g acid and vitamin C432 mg, with an edible rate of 96.3%, while 100g dried jujube contains 75.6g sugar, 1.58g acid and only 16mg vitamin C.

Under natural conditions, jujube will lose water quickly without any treatment at room temperature. due to much water loss and abnormal metabolism, the pulp tissue is saccharified, the loss of vitamin C is serious and the nutritional value decreases. Only through effective storage and preservation can the nutrients of fresh jujube be preserved to the maximum extent and the market competitiveness be improved.

1. Storage characteristics

The storage characteristics of Jun jujube mainly include the following aspects: high respiratory intensity of ①. Junzao belongs to respiratory jump type fruit, and its postharvest respiratory intensity is about 2 ~ 3 times that of red Fuji apple, which is the root cause of postharvest storage intolerance of Junzao. ② loses water quickly. The skin of Jun jujube is thin, the epidermis is underdeveloped, and the water is easy to evaporate. fresh jujube loses its freshness and brittleness in 2 ~ 3 days after harvest. The water loss of Junzao with low maturity is faster than that of Junzao with high maturity. ③ is sensitive to carbon dioxide. When the volume fraction of carbon dioxide in the storage environment is higher than 2%, it will aggravate the softening and browning of Junzao, but it is less sensitive to hypoxia and can tolerate 1% hypoxia under the condition of 0 ℃. The maturity of ④ has a great influence on the storability. Early red jujube was the most resistant to storage, followed by semi-red fruit, and full red fruit was the least resistant to storage.

two。 Pre-harvest management

The pre-harvest management of Junzao mainly includes three aspects:

① reduces pesticide pollution. Strictly control the application amount of pesticides, in the effective concentration range, try to use low concentration to control diseases and insect pests, generally limit the use of pesticides can only be used once a year, 20 days before fruit picking should be stopped, in order to ensure that there are no pesticide residues in jujube. ② inhibits ethylene metabolism. The ethylene concentration and respiration intensity of jujube fruit peaked with the ripening of jujube fruit. Junzao jujube was sensitive to ethylene in the white ripening stage and insensitive to ethylene after coloring and ripening. Therefore, the timely use of ethylene biosynthesis inhibitors such as aminooxyacetic acid and aminooxyvinylglycine is beneficial to enhance the storability of Junzao. ③ increased fruit firmness. Calcium can form calcium pectin with pectic acid in the colloidal layer of jujube fruit cells, which plays an important role in maintaining fruit firmness, regulating tissue respiration and delaying senescence. Therefore, spraying 0.2% calcium chloride solution on the crown and jujube fruit half a month before harvest can enhance the calcitonin content of Junzao and improve its storability.

3. Warehouse disinfection

The warehouse should be cleaned and disinfected half a month before the harvest, and the refrigeration equipment, electrical equipment and other facilities should be maintained and repaired. When disinfecting the warehouse, 15g~20g sulfur can be used to fumigate 24h~48h for every 1 cubic meter of space, or 1% to 2% formalin or 84 disinfectant and 0.5% bleach can be used to spray the wall and floor. The tools and containers used in the warehouse can be disinfected by soaking or whitening the calcium hypochlorite solution with a mass fraction of 0.25%, or they can be exposed to the sun.

4. Harvesting method

It is strictly forbidden to knock or shake trees during harvest. Pick them with your hands and do them gently. Practice has proved that retaining fruit stalk is an important measure to improve the storability of Junzao. After the jujube fruit is harvested, the jujube should be graded according to the size of the jujube, and the diseases, insects, deformities and injured jujube should be eliminated.

5. Pre-cooling treatment

Pre-cooling treatment is a necessary link to improve the storage and fresh-keeping effect of Junzao. Its purpose is to quickly disperse a large amount of field heat and reduce the cold load of human storage. In addition, the pre-cooling treatment can also avoid the chilling injury phenomenon which is easy to occur because Junzao enters the cold storage state immediately. It is best to cool down to about 0 ℃ within 24 hours after picking Jun jujube. Jujube pre-cooling can be carried out in the pre-cooling room in the cold storage or through forced ventilation, or it can be placed in a ventilated and cool place for 2 to 3 days to make the temperature close to the temperature of the storage room.

6. Fresh preservation and storage

At present, the widely used storage and preservation methods are fresh-keeping agent, mechanical refrigeration, controlled atmosphere and other fresh-keeping methods. in addition, some efficient and energy-saving storage and preservation methods such as natural cold source, high voltage electrostatic field and electric functional water are also on the rise.

(1) the cold storage method of fresh-keeping bag according to the actual conditions of storage and preservation at the present stage, the storage and preservation of Junzao jujube should adopt the cold storage method of fresh-keeping bag, and the air relative humidity in the fresh-keeping bag should be controlled within the range of 90% and 95%. The fresh-keeping bag can eliminate the harmful gas produced during the storage of Junzao in time. Put the fresh-keeping bag into a plastic box, each box is packed with 10kg jujube, fasten the mouth of the bag, and then store it in pallets. The temperature in the storage should be controlled within the range of-1 ℃ ~ 0 ℃, and the volume fraction of carbon dioxide is less than 2%. In order to maintain a stable state of low temperature, the fluctuation of reservoir temperature should not exceed 1 ℃, and the fluctuation of product temperature of Junzao should not be more than 0.5 ℃. In this environment, jujube can be stored for 60 to 100 days, and the rate of good fruit can reach 50% to 90%.

(2) controlled atmosphere storage has the best effect among many storage methods.

The controlled atmosphere storage temperature and humidity are the main factors affecting the storage effect of jujube fruit. The appropriate temperature is-1 ℃ ~ 0 ℃ and the relative humidity is 90% ~ 95%. After storage, the fruit tastes good and its flavor is maintained.

High volume fraction of carbon dioxide can cause fruit poisoning or anaerobic respiration, and accelerate the softening and browning of jujube. The appropriate gas index should be 2%-4% of carbon dioxide and 3%-6% of oxygen.