Lychee, which is known as the “Four Fruits of the South†together with bananas, pineapples and longan, is a very popular fruit. The flesh is translucent and has a sweet taste. Since the end of May, Litchi has been listed. It includes many varieties. According to the maturity time, there are March red, white sugar millet, scorpion laugh, black leaf, white wax and so on.
The color and flavor of the lychee is good. However, it has two limitations. First, it is geographically. It grows only in tropical and subtropical humid regions and is difficult to grow widely. Secondly, the preservation period is short. The ancients discovered this very early. Bai Juyi pointed out in the "Litchi Picture Sequence": "If you leave the branch, it will change in one day, and it will change on the second day. Four or five days away, the color and fragrance are all gone." Just a few dozen words, refining the process of litchi corruption. It can be seen that the preservation period of lychee is very short, and fresh lychee is a problem.
Why is it difficult to keep lychee fresh:
The lychee corruption process mentioned above only takes three or four days. Why is lychee corrupted so quickly? This is to start with its structure. The pericarp of the litchi contains a large amount of phenolic compounds, in which the polyphenol oxidase reacts with oxygen in the air, which causes the conversion of phenolic organic substances into terpenoids, and the accumulation and polymerization of terpenoids causes the red color of the peel to disappear. It turns brown. The peel also contains the hormone ethylene that promotes fruit ripening, which also accelerates the corruption of fresh fruit. In addition to the structure of the lychee itself, the external environment is also an important factor. As mentioned above, the harvesting time of lychee is in the summer of higher temperatures. Generally speaking, the temperature rises, the respiratory intensity of plant organs also becomes stronger, and the breathing consumes a large amount of nutrients, which leads to the aging of fresh fruits and is difficult to resist the invasion of germs.
Ancient lychee preservation method:
After analysis, we saw that the lychee is difficult to keep fresh mainly in the chemical reaction of oxygen and peel. Although the ancients did not have such scientific consciousness, they knew that the fresh lychee needs to be isolated from the air. The ancient method of lychee preservation was sealed and the most popular red was selected. The lychee, then find a big bamboo, cut a hole and put the lychee into it, then use bamboo to lay it up, but also wrap some mud seal, after the seal, the gas in the bamboo will moisten the lychee. In this way, lychee can be hidden in the second winter.
Modern lychee preservation method:
In the modern technology developed, with the advent of cold chain transportation equipment such as cold storage, freezer and refrigerated trucks, Litchi broke the magic spell of “Four Days and Five Colors and Scent†and the shelf life was extended. After the lychee is harvested, it is not easy to be spoiled in the environment of 4 ° C - 14 ° C. Therefore, many cold chain logistics facilities have been perfected to extend the storage period of lychee. For example, Lingshan has built more than 40 cold storages for litchi. Haikou and the e-commerce platform transport the packaged litchi products through cold chain cars... The establishment of these cold chain logistics facilities enables the litchi to be stored and transported in a cooler environment. To achieve an extension of the shelf life. Litchi receives pre-cooling and storage from the harvest, and the shorter the time, the better.
According to Australian reports, 52% of the 0.05% benzoate solution was used to soak the fruit for 2 minutes, dried and placed in a square plastic box covered with a 0.01 mm polyethylene film, which was stored at room temperature for 7 days. There is also a good effect of Tekto (TBZ) or carbendazim 100ppm soaked fruit 2 - 3 minutes, 0.5% sodium sulfate or 2% sodium hypochlorite for 2 minutes. Removal of normal temperature storage, as well as quick-freezing storage, fresh lychee is scalded with hot water to inhibit the activity of epidermal enzymes, prevent discoloration, and then quickly freeze at a low temperature of 20 ° C - 28 ° C, and then at about 20 ° C In the middle of storage, the supply market can be taken out at any time.
The above method is suitable for merchants to sell lychee. How do we keep lychee in our daily life?
Daily storage method of lychee:
In our daily life, fresh lychees are generally selected for easy preservation. First cut the long branches of the lychee, then put the lyche into the crisper and place it in the shade. If you have the conditions, you can soak the plastic bag with lychee in the water. This simple method can keep the lychee fresh for a few days.
If you want to keep it longer, you can throw away the bad lychee, and the remaining healthy lychee cuts off the branches and leaves only a small pedicle, and packs 20-30 lychees with some fresh lychee leaves in the newspaper. After placing the plastic bag, place it on the fresh-keeping layer of the refrigerator. It should be noted that it is necessary to check frequently to ensure that the litchi is not broken and that the newspaper is in a dry state. This method can save the litchi for about ten days.
If you still want to save longer, you have to work hard. Take the ripe lychee together with the leaves and pick the healthy lychee and put the leaves together in a clean ceramic pot. Then take the appropriate amount of lychee honey and boil. It is also added to the ceramic tank, and finally it is sealed and sealed, and the tank mouth can be sealed with wax. Place the pots in a ventilated and dry place. In this way, the litchi can be kept fresh until the second year of New Year's Day.
Conclusion:
The current lychee preservation technology has been improved, and the development of food machinery and equipment and the advancement of technology have greatly facilitated our fresh lychee. From the above analysis, there are two physical and chemical methods for lychee preservation. The physical method is mainly based on low temperature refrigeration. This method is realized by means of food machinery, and the preservation effect is the best. However, the current technical conditions can not achieve the need for long-distance transportation and sales, and a difficult point of lychee preservation. It is believed that with the continuous development of food machinery, more and more perishable fruits can achieve fresh food.