Study on Storage and fresh-keeping of Jujube

Jujube is one of the unique fruit trees in China, which has been cultivated for more than 2000 years. Jujube is resistant to cold, drought and barren, and has strong adaptability. It is known as "iron crop". Jujube fruit is rich in nutrition, contains more than twice the sugar content of ordinary fruit and more protein, fat, iron, phosphorus, calcium and other substances, has a high nutritional value and dietotherapy function.

The domestic research on the storage and postharvest physiology of fresh jujube began in 1980. The postharvest physiology and storage of jujube were studied and explored, and a lot of work was done on the physiological and biochemical mechanism, but in the storage technology, that is, there is no new breakthrough in prolonging the storage period of fresh jujube.

Progress in Storage conditions and Technology

In our country, people have the habit of eating fresh dates, and they have also accumulated some fresh-keeping methods. There are records of fresh dates preserved in the ice cellar in the archives of the Qing Palace, with a storage period of less than one month. In the past ten years, many scientific research and teaching institutions have done a lot of research and exploration on the storage conditions and technology of fresh jujube. the results show that the storage of fresh jujube is affected by many factors.

1. Variety

The storage tolerance of fresh jujube varies greatly with different varieties. According to the storage resistance tests of 30 varieties collected from Taigu and Shanxi fruit trees in Shanxi, Xiangfen round jujube, Linfen round jujube and Yongjiha Oviductus Ranae had the best storage resistance. Taigu Hulu jujube, Tuntun jujube and Xiangzao jujube are in the middle, while Lang jujube and Junzao are the worst.

2. Harvest maturity

Harvest maturity has a significant effect on the storage life of fresh jujube, the lower the maturity, the more resistant to storage, but the rate of water loss of fruits is faster than that of fruits with high maturity.

3. Environmental conditions

Temperature.

Temperature is the most important environmental factor affecting the storage life of fresh jujube. In a certain range, the lower the temperature, the better the storage effect, but frostbite will occur when it is below the freezing point. According to the determination, the freezing point of semired Lang jujube is-2.4 ℃ 3.8 mol.

Humidity

Fresh jujube is a kind of fruit which is easy to lose water. The water loss rates of Lang jujube, Hongxing apple and Hawthorn stored for 14 days were 22.2%, 1.2% and 11.2% respectively under the condition of 6-10 ℃ and 70%-80% relative temperature, respectively, indicating the importance of maintaining high humidity for fresh jujube storage. Using 0.03~0.06mm PVC punching bag to store fresh jujube has a good moisturizing effect.

Gas composition

Different gas composition tests showed that fresh jujube could not tolerate carbon dioxide, and carbon dioxide higher than 5% would accelerate the softening and browning of fresh jujube pulp. In the case of basically no carbon dioxide, 1.5% low oxygen did not soften and turn brown earlier than the air control, indicating that fresh jujube is more sensitive to carbon dioxide than to low oxygen.

4. Other physical and chemical methods

Calcium is an important component of the gum layer in fruit cells. many studies have shown that calcium treatment can improve fruit firmness and storage life. Lang jujube was soaked in 2% calcium chloride immediately after harvest, and the rate of good fruit after 2 months storage was 20% higher than that of the control. Junzao jujube was treated with 5% calcium chloride for 5 minutes before storage, and the hard fruit rate was 15.6% when stored in a perforated bag for 70 days under the condition of 0 ℃, while the hard fruit rate of the control was 6.2%. However, some studies have shown that there is no obvious effect of soaking fruit with calcium chloride compared with the control.

In recent years, the research on the storage of fresh jujube continues, and many physical and chemical methods such as coating film, preharvest hormone treatment, cobalt 60 radiation treatment, vacuum preservation, electromagnetic radiation, rapid cooling, heat treatment and so on have been discussed. although some methods have a certain effect on delaying the softening of jujube fruit, it has not been seen to have a significant effect. New methods and techniques are still being explored.