Controlled atmosphere storage is a modern storage technology developed on the basis of traditional cold storage, which is considered to be the best storage method for fruit storage. Commercial atmosphere controlled storage has been abroad for more than 60 years. In developed countries, long-term storage of fruits is mostly controlled by atmosphere storage. The controlled atmosphere storage in China began in the 1970s. In the past 30 years, through the introduction, digestion and absorption of advanced technology and equipment from abroad, together with the continuous research and exploration by Chinese researchers, the technology of controlled atmosphere storage has been rapidly developed. Now has the ability to design and build a variety of air-conditioning libraries and air-conditioning equipment.

I. principles of controlled atmosphere storage

Normal air generally contains 21% oxygen, 0.03% carbon dioxide, and the rest is nitrogen and some trace gases. Fresh fruit is still a living body after harvest. During storage there is still a normal metabolic activity dominated by respiration which mainly shows that the fruit consumes oxygen and at the same time releases a certain amount of carbon dioxide and heat. Carbon dioxide (CO2) and ethylene released from fruit have significant effects on respiration of fruit.

Reducing the oxygen concentration and increasing the carbon dioxide concentration in storage environment can inhibit the respiration of fruit, delay the ripening and senescence of fruit, and prolong the storage period of fruit. Low temperature and low oxygen and high carbon dioxide could inhibit the synthesis of ethylene and weaken the effect of ethylene on fruit ripening and senescence, thus reducing or avoiding the occurrence of some physiological diseases. In addition, low concentration of oxygen and high carbon dioxide in the environment can inhibit the growth and spread of fungal diseases.

II. Advantages of controlled atmosphere storage of (CA)

storage time of the long-time air-conditioned storage is combined with the technology of low-temperature (cold storage) and the adjustment of the gas components in the storage environment, so that the storage period of the fruit can be prolonged to a great extent. Under controlled atmosphere storage, the annual supply of apples can be achieved; the pear and the pear, the pear, the pear and the like can be stored for 8 to 9 months, and the stored kiwifruit of the modified atmosphere storage is extended for 2 to 3 months more than the cold storage period.

(2) the fresh-keeping effect is good. After long-term storage, most of the fruits, such as middle-late ripe apple and pear, long-held pear, fragrant pear and so on, still have bright color, green fruit handle, pure flavor, plump appearance and similar to that of the fresh harvest time. Taking apple as an example, the flesh hardness, titratable acid and other indexes after controlled atmosphere storage were significantly higher than those of fruits frozen at the same time.

(3) Storage loss, low atmosphere controlled storage strictly controlled the temperature, humidity, oxygen and carbon dioxide in the storage, which effectively inhibited the respiration, transpiration and microbial damage of fruits, and lost water during storage. The loss caused by decay, etc., is greatly reduced. According to the observation of kiwifruit by Henan Institute of Biology, under the same storage period, the loss of common cold storage is as high as 15% and 20%, while the total loss of controlled atmosphere storage is less than 4%. After storage for 10 months, the water loss rate was almost zero for a certain air-regulated Kuyali pear in Hebei province.

(4) the long shelf-life fruits after controlled atmosphere storage still have a long period of "lag effect" after releasing the atmosphere-adjusted state due to the long-term low oxygen and high carbon dioxide effect. According to Shaanxi's experiments on apples, it is generally believed that the shelf life of controlled atmosphere storage is 3 times as long as that of cold storage on the premise of maintaining the same quality.

(5) "green" storage in controlled atmosphere storage of fruit, due to the interaction of low temperature, low oxygen and relatively high carbon dioxide, can basically inhibit the occurrence of infectious diseases. In the course of storage, chemical drugs are not used for antiseptic treatment.