The lychee known as the “Four Big Fruits of the Southland” along with bananas, pineapples, and longans is a popular fruit. The flesh of the fruit is translucent and creamy. The taste is sweet. From late May onwards, litchi has been listed. It includes many varieties, According to the mature time, there are red in March, sugar millet, dumplings laughter, black leaf, white wax and so on.
The color, flavor and taste of litchi can be described as good. However, it has two limitations. First, it is geographical. It only grows in humid tropical and subtropical areas and is difficult to grow widely. The second is the short shelf life. The ancients discovered this very early. Bai Juyi pointed out in the “Lychee Pictorial Sequence”: 'If you change from this branch, it will change color on one day, but it will change on the second day, and change on the third day. After four or five days, the color and flavor will go away.' Dozens of words summed up the process of litchi corruption. It can be seen that the preservation period of litchi is very short. Fresh litchi is a difficult problem.
Why litchi is difficult to keep fresh:
As mentioned above, the litchi process only takes three or four days. Why does the litchi decay so quickly? It starts with its structure. Litchi's skin contains a large amount of phenolic compounds, in which polyphenol oxidase and air The oxygen in the reaction causes the conversion of phenolic organic substances into quinones, and the accumulation of quinones causes the redness of the peel to disappear and turn brown. The peel also contains the hormone ethylene that promotes fruit ripening. Accelerate the corruption of fresh fruit. In addition to the structure of lychee itself, the external environment is also an important factor. As mentioned above, litchi is harvested during the summer when the temperature is high. In general, the temperature rises and the respiratory intensity of the plant organs also increases. When it becomes stronger, the breath will consume a lot of nutrients, resulting in aging of the fruit, and it is difficult to resist the invasion of the bacteria.
Ancient litchi preservation method:
After analysis, we can see that the difficulty in keeping fresh litchi lies in the chemical reaction between oxygen and peel. Although the ancients did not have such a scientific awareness, they knew that preservation of litchi requires the isolation of air. The method used by the ancients for the preservation of litchi was the sealing method. Litchi, then find a large piece of bamboo, cut a hole and put the lychee in, put it on bamboo, and put some mud in it to seal it. After sealing, the air in the bamboo will nourish the lychee. With this method, the litchi can be Hide into the second winter.
Modern litchi preservation method:
In the modern, technologically advanced world, with the advent of cold storage, refrigerators, and refrigerated trucks, the litchi has broken the curse of 'Four Days and Five Colors', and the shelf life has been extended. After litchi is harvested, if Put in 4 °C -14 °C environment is not easy to corrupt, so many began to improve the cold chain logistics facilities to extend the shelf life of litchi. Lingshan, for example, built more than 40 cold storage for litchi, Haikou, together with the e-commerce platform through the cold chain car will The packaged litchi products are transported out... The establishment of these cold chain logistics facilities allows Litchi to be stored and transported in a relatively low temperature environment to achieve a longer shelf life. Litchi receives pre-cooling from storage, and is stored in storage for shorter periods of time. it is good.
According to reports in Australia, 52% of 0.05% Benzoate solution was used to dip fruit for 2 minutes, and after drying, it was put into a square plastic box and covered with a polyethylene film of 0.01 mm. It can be stored at room temperature for 7 days. There is also Tec. More (TBZ) or carbendazim 100ppm fruit dip 2 - 3 minutes, 0.5% sodium sulfate or 2% sodium hypochlorite dipping fruit for 2 minutes also have good results. Remove the normal temperature storage, there are quick-frozen storage, fresh lychee with hot water immersion Hot, Inhibit epidermal enzyme activity, prevent discoloration, and then quickly frozen at -20 °C - 28 °C low temperature, and then stored at about minus 20 °C, you can remove the supply market at any time.
The above method is suitable for merchants selling lychee. How do we preserve lychee in our daily life?
The daily preservation method of litchi:
In our daily life, we usually pick fresh lychees for easy storage. Cut the long branches of lychee first. Then put the lychee in the crisper and place in the shade. If possible, soak the plastic bags in the water. , This simple method can keep litchi for several days.
If you want to preserve it for a long time, you can throw away the bad lychees. The remaining healthy lychees cut off the branches leaving only a small pedicle, and 20 – 30 lychees plus some fresh litchi leaves in the newspaper. Put on the plastic bag and put it in the refrigerator's fresh-keeping layer. It should be noted that you should always check to make sure that the litchi is not broken and that the newspaper is in a dry state. This way you can save the litchi for about ten days.
If you still want to preserve it for a long time, you have to work hard. Take the mature lychee with the leaves and leaves. Pick the healthy litchi with leaves and put it in a clean ceramic jar. Then take the appropriate amount of litchi honey and boil it. Afterwards, ceramic jars are added. Finally, the lids are sealed and the mouth of the jars can be sealed with wax. Place the jars in a ventilated and dry place. In this way, litchi can be kept fresh until the following New Year's Day.
Conclusion:
The current litchi preservation technology has been improved. The research and development of food machinery equipment and technological advancements provide us with great convenience for fresh litchi. From the above analysis, there are two physical methods and chemical methods for the preservation of litchi. Physical The method is based on cryogenic refrigeration. This method is implemented with the help of food machinery, and the preservation effect is the best. However, the current technical conditions cannot achieve the need for long-distance transportation and sales. At this time, it is a difficult point for preservation of litchi. The continuous development of machinery, more and more perishable fruits can achieve fresh food.