Lychee is of high nutritional value, with a moisture content of 84 g, carbohydrates of 14 g, fat of 0.6 g, protein of 0.7 g, vitamin C of 36 mg, riboflavin of 0.04 mg, and niacin of 0.4 mg per 100 g of pulp. Litchi is one of the most intolerant fruits. Each year, the loss caused by decay in China accounts for more than 20% of the total output. Since the 1980s, the application of advanced technology and equipment has made some promising progress in litchi preservation technology, but the fundamental issue of preservation of litchi has not yet been resolved. Therefore, to further improve the preservation of litchi, it is of great significance to ensure market supply, increase the income of farmers and foreign exchange through exports. There are many methods for the preservation of litchi. People often classify them into three categories according to the storage temperature and the length of storage, namely: normal temperature storage method, zero-low temperature storage method, and zero-low temperature fast freezing storage method. 1. Room temperature storage method has low storage cost at room temperature and does not require special equipment. It is suitable for short-distance transportation and air transportation. The general preservation period is 5 days. Liang Hanhua from the Hong Kong Polytechnic University and Ji Zuoliang and Huang Xiaoyu from the South China Agricultural University believe that after bleaching at 500 цg/1, pre-cooling at 14-20°C, treatment with B-aluminophosphate, azole and ethylene sorbent, foam foam packaging is used. + Ice packaging, this simple cooling storage method combines the features of controlled atmosphere refrigerated storage and room temperature storage. After 5 days of storage of litchi, the commodity rate reached 94.77%. Chen Zhihong and others studied the preservation effect of Chinese herbs, radix lucidum, polygonum cuspidatum, prickly ash, clove, and cinnamon on Litchi. It was found that the use of Chinese herbal medicines in combination with ethylene absorbers and polyethylene plastic packaging can keep litchi preserved at room temperature for 10 days. The flavor. With modified atmosphere technology and necessary anti-corrosion and color protection measures, Litchi has been preserved for about a month and has been used for commercial storage of litchi. At low temperature, the respiration, ethylene release, and ACC synthesis of litchi fruit were all decreased, but the electrolyte leakage rate of litchi pericarp cells was increased at low temperature. When the exudation rate reached 50%, the fruit suffered irreversible cold injury, browning and decay, and thus low temperature When the lower litchi storage time exceeds one month, the commodity rate decreases. Low-temperature supplemented by modified atmosphere technology better storage of lychee, you can use spontaneous air-conditioning (MA storage), that is, polyethylene plastic bags, through litchi own respiration to change the ratio of carbon dioxide / oxygen in the plastic bag, and then reduce Lose water, reduce respiration, and extend storage life. Artificial low-temperature air-conditioning storage method (MA storage) can also be used. After fruit collection, wet pedicle, diseased fruit and mechanically damaged litchi fruits are removed as soon as possible, and then preserved in a 0.25-mm-thick polyethylene plastic bag. 2.5kg, bag filled with different concentrations of carbon dioxide and oxygen, stored in a 1-3 °C cold storage, the relative humidity inside the library is maintained at about 90%, every 2 to 3 days to adjust the gas inside the sealed container, glutinous rice, carbon dioxide and oxygen Each was 5%, and the good fruit rate reached 91% after 30 days. The best gas combination for Huaizhi is 10% carbon dioxide and 3% oxygen. Due to the complexity of operations and the need for certain equipment, the domestic air-conditioned and preserved fresh litchi has not yet been commercialized. Precooling problem. Litchi is generally pre-chilled before storage. The effect of pre-cooling is mainly to reduce the respiratory intensity, inhibit the activity of pathogens, and also improve litchi resistance to cold and reduce the occurrence of physiological diseases. Ice-water liquid has both preservative and pre-cooling effects, which is a convenient and practical pre-cooling method. The ice water solution is generally controlled at about 5°C, and the fruit is soaked for 5-10 seconds. Generally, the fruit temperature will be reduced by about 10°C. After the precooling, it should be stored in the cold storage immediately. 2. Zero-temperature, quick-frozen storage Quick-freezing and preserving methods are usually frozen at a low temperature below -23°C, packaged in plastic film, and then refrigerated at -18°C and 95%-100% relative humidity for more than one year. The process flow is: selecting fruit → disinfecting → rinsing → color protection → quick freezing → packaging → refrigeration. One of the key issues in the production of frozen lychees is color protection and browning. The color control fluids that are more commonly used today are mixtures of citric acid and salt. In general, the quick-freezing temperature is closely related to the quality of the quick frozen fruit. The lower the quick freezing temperature, the smaller the ice crystals formed in the frozen fruit tissue, the better the quality of the fruit, and the longer the color retention after thawing. In terms of color protection research, scientists have done a lot of useful attempts. Wang Shaofeng and others used the F4-LC litchi fresh-keeping protection agent to treat the frozen lychee. The color-protecting agent GOS-L89, developed by the scientific staff of the South China Institute of Botany, Chinese Academy of Sciences, can process frozen lychees for 8-10 months, with a shelf life of 2-3 days. In South Africa, Australia, Israel, and other countries, sulfur-smoked, dilute hydrochloric acid, and then red frozen storage method. There is a problem with frozen lychee. Due to the destruction of the cell tissue caused by freezing, the skin of the thawing is quickly browned, and the flesh of the fruit is soaked in water. The fruit cracking problem is also serious. Fruit pre-cooled to near 0 °C, or frozen in plastic bags, can reduce the rate of cracking.