Litchi Storage and Transportation Technology
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Litchi is a subtropical fruit originating in southern China. Because of its unique color and fragrance, it is deeply loved by people. It is known as "Zhongguozhiguo" and it is one of the most competitive fruit in the international market in China. However, due to its maturity in the midsummer high temperature season, coupled with its special structure, strong metabolism, perishable deterioration after picking, easy browning of the peel, which brings great difficulties to the storage and transportation preservation work. (I) Storage characteristics Litchi is a non-breathing peak fruit. The intensity of respiration on the day of harvest is high and gradually decreases with the extension of time, but it is still 2 to 3 times higher than that of apples, pears, oranges, bananas, etc. When the fruit turns brown and rot, the respiratory intensity rises again and there is no significant respiratory peak. Ethylene release from litchi was always kept at a low level, and there was no significant ethylene peak. In the mature and aged process of litchi, the effect of ethylene was not obvious. Therefore, to do a good job of storage and preservation of litchi must take all feasible ways to reduce the respiration of Litchi fruit. If lychee is precooled as soon as possible after harvest, storage under proper low temperature conditions is one of the important means to reduce the respiratory intensity of litchi and prolong its storage life. Litchi fruit structure is very special, exocarp cuticle is very thin, there are many small cracks in the cracks, the middle is loose sponge tissue, so the water is easily lost; In addition, the peel and pulp completely separated in the structure, no conduction organization connected when When the skin is dehydrated, although the pulp has sufficient moisture, it is difficult to supply the peel, so the peel quickly loses water and browns. Therefore, the phenomenon usually seen is that the skin is dry and dark, while the flesh still maintains a fairly full moisture content. At room temperature without packaging, all litchi placed for 3 days turned brown and the weight loss rate of the pericarp could be as high as 50%. It can be seen that the more it is in dry heat, the more important it is to moisturize the skin. It can be said that moisturizing is preservation. Litchi browning is fast, and it is rare in other fruits. Generally, litchi changes brown within 24 hours after picking. At room temperature, it loses the attractive bright red and browning after 2 to 3 days. The commercial value of litchi. The factors causing the browning of the litchi peel were, in addition to the dehydration of the peel, the infection, infestation, thermal damage of the pathogen, and the senescence of the fruit itself. The internal cause of browning is enzymatic browning. Polyphenol oxidase and peroxidase are present in the litchi pericarp. The pericarp also contains a large amount of phenolic substances (including the red pigment of the litchi skin). Under aerobic conditions, these The enzyme acts as a biocatalyst that oxidizes the phenols into a dark brown substance. Recent studies have shown that peel browning is also related to the fading or discoloration of its red pigment, ie, anthocyanin. The color of anthocyanin depends on the pH of the environment where it is present. Improve, the color changes from red to colorless, and then become purple, purple and black, such as the use of alkaline dissolved lychee treatment of fresh litchi, litchi immediately turned black, if the solution is processed, it can restore red. The rapid dehydration of the litchi skin resulted in an increase in the pH of the peel. This accelerates the occurrence of browning. From the above analysis, it can be seen that controlling litchi browning should start from several aspects: 1 Use appropriate moisturizing packaging to reduce dehydration of the peel. 2 Reducing respiratory intensity and delaying fruit senescence, such as pre-cooling, low-temperature storage, and modified atmosphere storage. 3 inhibition of polyphenol oxidase activity, such as modified atmosphere storage, the use of polyphenol oxidase inhibitors such as sulfur dioxide. 4 reduce the pH of the fruit, such as acid treatment. (B) Storage diseases 1. Litchi chinensis Phytophthora chinensis Litchi chinensis is the most serious disease on litchi fruit. Not only does it cause serious losses during fruit storage and transportation, but it also causes a lot of fruit drop and rotten fruit when it encounters cloudy and rainy weather during fruiting period in the field. In severe cases, the loss can reach 30% to 80%. In some years, the pre-acquisition weather was clear and cloudy, and the appearance of the fruit was good. However, the disease was outbreak in post-harvest transport, which caused heavy losses to the sales department. [Symptoms] Young litchi fruit, ripe fruit, stalks, and fruiting branches can all be affected. However, serious damages and large losses are mainly caused by ripening fruits and fruits during storage and transportation. When the result was victimized, more blemishes, irregular spots, and spots with no obvious edges appeared on the pedicel, and a white mold layer grew on the surface when wet. The lesions expand rapidly, often turning the whole fruit brown, flesh rot, acid rot and brownish juice. Symptoms are more difficult to distinguish from acid rot. [Pathogenesis] Germs can overwinter on diseased leaves and diseased fruits. In the late spring and early summer of the following year, sporangia are produced and spread by wind and rain. The disease during storage and transportation mainly comes from the healthy appearance of the field, but has been invaded by the bacteria, and under appropriate conditions, continue to contact the disease. The occurrence and prevalence of diseases are most closely related to the level of humidity. Pathogens require high humidity at all stages of the infestation process, otherwise they cannot be compromised. Under high humidity conditions, pathogenic bacteria can invade fruit at 11-30°C, and the most suitable expansion temperature is 25°C. Therefore, in the field of fruiting in the field, in the event of continuous rainy weather for more than 4 to 5 days, the disease will be severe. During storage and transportation, moisturizing packaging helps to prevent peel browning, but high humidity environment is easy to induce severe Phytophthora capsici. [Prevention and control methods] The control of rotten fruit during the storage and transportation of lychee caused by Phytophthora infestans is not very effective due to anti-corrosion and low-temperature storage and transportation of the pesticide after harvest. The focus should be on orchards. (1) Do a good job of orchard sanitation, clear the fruit, rotten fruit, and litter on the trees and the ground, and burn them together. Reduce the source of the disease. (2) From the first week before flowering, regular spray protection fungicide, a total of 3 to 4 times, each time interval of 2 to 3 weeks. For example, 25% of Bacillus subtilis 500-600 times or antiviral 600 times, or 80% alfa-aluminum 400 times, or 75% chlorothalonil 500-800 times, 70% thiophanate-methyl 1500-fold. (3) After fruit picking, the fruits for storage can be immediately soaked with Rhizoctonia or acetylphosphorus 1 ‰ + tetrodol (or sigong) 1 ‰ solution in the place of production. If the sterilizer is soaked with ice water ( 5~10°C liquid soaking for 5 to 10 minutes), so that the pre-cooling and anti-corrosion treatment are carried out at the same time, the effect is better. After the fruit is dried, it is sent back to the cold store to continue pre-cooling. The fruit temperature is reduced to 7～8°C, and then in the cold storage. Select fruit packaging. 2. Litchi acid rot Sour rot disease is a common disease of litchi fruit, which mostly occurs in larvae and ripe fruit. It is a relatively serious threat during storage and transportation. The incidence rate is sometimes more than 10%. [Symptoms] Major hazards to ripening fruit or pests, usually from the pedicle of the fruit. The lesions are brown irregular spots, then gradually enlarged to brownish rot of the whole fruit, the pulp is sour and rancid, the peel hardens, turns dark brown Out of acid water, the disease minister had a layer of white mold (sprout spores). [Pathogenesis] Germs are widely distributed in the soil and spread by wind and rain or insects. During the storage and transportation of fruits, they are infected by disease or fruit, or invaded by wounds. Fruits that are damaged by litchi, elephant moths, and caterpillars, or fruits that are mechanically damaged during fruit picking, are susceptible to disease, but are often not easily detected when harvested. [Control methods] (1) Strengthen cultivation management and prevent and control litchi pests in time. (2) Harvesting and transportation to avoid damage to fruits and fruit pedicles, and in particular, it is not advisable to use sharp scissors to collect su. The handle of the ear is cut flat to avoid stabbing the fruit. (3) Immediately dip the fruit with the liquid after fruit selection. Litchi post-harvest anti-corrosion commonly used B-aluminum, Rhizobium, Tecdo, carbendazim and other agents can not control the acid rot, so add imazalil 1 or double guanidine salt 1 anti-acid rot. (4) Treating with hot liquid after picking fruits can find and remove pests early. 3. Litchi Anthracnose Anthracnose is a common disease on litchi leaves. It currently causes less damage and is an expanding, noteworthy disease. Sensitive disease of young fruit, causing early fruit drop, more mature or immature fruit. It usually occurs at the end of the fruit. The lesions are round, brown and brown on the edges. Sometimes the center of the lesion produces orange-red sticky granules. In terms of prevention and control, it is mainly used in combination with carbendazim or thiophanate-1 for antiseptic treatment in combination with the control of Phytophthora capsici. (C) Storage Technology 1. Harvest litchi for storage, harvest maturity to eight mature appropriate, at this time litchi peel basically red, turtle crack with tender green or yellow-green, inner skin is still white, but Huaizhi varieties can be harvested when the endocarp at the near pedicle shows red turning. When ripe litchi is eight, the fruit content is almost close to the highest value, and the ratio of sugar to acid is about 70:1. If the maturity is too high and storage is not tolerated, the dark skin color is a sign of overcooking. Fresh food should not be allowed for long. It is advisable to harvest on a sunny day in the morning or on a cloudy day. It should not be harvested in the rainy days, after the rain, and in the hot sun. When picking, it should be lightly folded and gently placed. The container for fruit packing should be hung on the tree. The ear should not be thrown on the ground. Try to avoid mechanical damage and ensure quality. Advocate short branches for fruit picking, that is, do not fold the leaves below the ear when picking, and keep 2-3 buds below the base of the ear. 2. The antiseptic treatment shall be treated with a bactericide on the day of harvesting. Generally, it shall be soaked with BPA (1‰) + Tecdo (1‰) for a while and then dried to select the fruit package. It has also been reported to be soaked in deep liquid with benzene concentration of 510 at 52°C for 2 minutes, or soaked in 0.5% copper sulfate solution for 20 seconds. In addition, Mi Xianan, imazalil, sec-butylamine etc. are also used as litchi in foreign countries. Antiseptic drugs have good results. 3. Select the fruit to remove the cracks, mechanical damage and pests and fruits, select the fruits with the same maturity to ensure the quality. Fruit branches can be retained, but the leaves must be removed to avoid increasing the concentration of carbon dioxide in the package due to excessive breathing, affecting the longevity of litchi fruit. The fruit selection should be done in a cool place or at a cold storage warehouse. 4. Remove mechanical damage and pests and diseases before packing and packaging. Litchi fruit has strong respiration, high heat of respiration, and the skin is very easy to lose brown water. Therefore, it is better to use a small package or ventilated medium-sized package that can both moisturize and cool down. The inner packaging can use 0.02-0.04 mm thick polyethylene film bag, the amount of packaging should not be too much, 0.5 to 1.0 kg is appropriate, polyethylene bags can be moisturizing and have the effect of spontaneous atmosphere. The outer packing can use perforated cardboard boxes, wooden boxes or bamboo baskets, and the loading capacity can be 10-20 kg in order to facilitate ventilation and heat dissipation. The short-term transport at normal temperature can be packaged in plastic baskets, wooden boxes, bamboo baskets, etc. The liners can be used to pad grass and leaves, and the polyethylene film around them can moisturize and facilitate ventilation. The load should not be too large, so as to avoid rot and browning caused by excessive temperature in the center of the package. 5. Pre-cooling pre-cooling is one of the key measures to prolong the shelf life of litchi. Litchi harvested in the hot season, the temperature of the fruit itself is high, and the respiration of litchi is particularly strong, and the heat of respiration is very large. Even if the fruit temperature is not easy to fall down in a colder cold store, it should be quickly cooled. As soon as possible, the temperature of the fruit should be lowered to the proper temperature for storage. The pre-cooling method can be diversified. When using dipping medicine, it can be dispensed with ice water, and the anti-corrosion and pre-cooling can be integrated, which is both quick and labor-saving. It can also enter the pre-cooling room for fruit selection and packaging after the antiseptic treatment, making full use of working time for pre-cooling. The simplest method is to quickly store the goods after packaging, place them separately to cool the heat, and store them until they are close to the temperature. Prechilled Litchi fruit can fall to storage temperature within 24 hours, while unpre-cooled fruits require 50-60 hours to fall to storage temperature, as shown in Table 10. The shorter the time from harvesting, packing, and storage, the better the storage effect. The effect of pre-cooling on the temperature drop of litchi into the storage is 3～5°C (Table 10) 6. Storage and transportation (1) Storage at normal temperature: Normal temperature storage is mainly based on the antiseptic effect of preservatives to achieve the preservation purpose, and also useful for preservation. The agent is treated with heat treatment to prevent corrosion. The preserved litchi is moistened with plastic film to prevent browning and decay. For example, China Agricultural College (1984) applies 1 liter of Benzene + 1 ‰ of aluminum diphosphoric acid to fruit, and is packaged in a 0.015 mm thick polyacetate-ethylene film (EVA) and can be stored at room temperature of 30-35°C. 7 to 9 days, the good fruit rate is above 90%. Some people try the ice cooling method for normal temperature storage and transportation, to achieve better results, the approach is: litchi first anti-corrosion pre-cooling, after drying with a polyethylene bag, into the foam plastic box, add ice cubes, cooling, fruit Ice ratio of 2:1, and then quickly shipped to the market, after 3 to 5 days, litchi is still fresh, the disadvantage is that the packaging is easy to accumulate high concentrations of carbon dioxide, resulting in litchi taste. The preservation time of normal temperature storage and transportation can reach 5 to 10 days, while the lychee that has not been processed for preservation is rotted in browning after 2 to 3 days after harvesting. However, the storage at normal temperature is a little careless, that is, causing huge losses. So far, it has not been possible to propose normal temperature storage technology suitable for large-scale production. (2) Low-temperature storage and transport: The low-temperature storage and transportation of litchi is the basis for controlling peel browning, reducing pathological decay and maintaining fruit quality. Litchi storage and transportation temperature is 3 ~ 5 °C, the temperature is too low will suffer cold damage, such as litchi at 1 °C under 30 to 35 days that began to chilling, peel browning and become taste. Litchi should not be allowed to change temperature during storage and transportation. Low-temperature combined with modified atmosphere has better storage effect. Different litchi varieties require different concentrations of oxygen and carbon dioxide. The concentration of carbon dioxide is preferably 3% to 5%, and the oxygen concentration is 5%. However, the requirements for atmosphere storage equipment are high. It is difficult to promote the production. At present, many methods for spontaneous storage at low temperature are used, namely, polyethylene film pouches of suitable thickness are used for packaging. Low-temperature self-regulation can make Lychee storage and transportation period of 30 to 40 days. (3) Sulfur-soaked and pickled acid treatment: Sulfur dichloride is the most widely used preservative in food processing and can inhibit polyphenol oxidase activity. It is also an effective bleaching agent and is therefore used to prevent enzymatic browning of litchi skin. Change and antiseptic. The treatment method is to burn 100g of 90% sulfur powder per cubic meter, fumigate the lychee for 15-30 minutes until the peel red fades and turns bright yellow. Sulfur dioxide gas (1% concentration) can also be directly released from high-pressure cylinders for fumigation. Sulfur treated litchi should be stored at a low temperature of 1 to 2°C and stored for 1 to 2 months. Otherwise, it is prone to mildew and rot. After the sulphur treatment, the red fruit can only be partially restored. It is well-known that artificial fruit on longan fruit can reduce tree load, reduce nutrient consumption, concentrate nutrition, promote young fruit development, and strengthen fruits and fruits. It is the production of longan that increases longan fruit, improves quality, and seizes longan. An important measure for high yield and stable production. If there is a reasonable result, I will work with the regional fruit production technical guidance station and Professor Lu Meiying of Guangxi University to study and discuss together a set of simple and easy-to-operate fruit removal methods. "," "short cuts, digging and sweeping." This simple method of fruit thinning was popularized and applied in large areas in Pingnan County. The effect was very good and it was very popular among fruit farmers. Here is the introduction, share with everyone. "See the four sparse ones" is the ear of the longan tree that sparse 25 trees. In the process of sparse spikes, the four ears are cut to remove the ear, and the whole ear is cut off together with the lower two to three leaves of the mother tree. After leaving the sparsely populated and evenly distributed the ear, call it "see the sparse one" and evenly sparsely and evenly. In the case of a stunted ear, remove it first. “Short cuts, digging hearts and sweeping sweeps†is to pulverize the remaining big ears. Firstly, the longan ear is gently disturbed by hand into bundles, and then the branches are cut at appropriate positions to make a short cut. This is the first step of “short cutâ€; then, loosen the hand to allow natural extension of the ear, and then use the branches to cut the axis of the ear. In part, this is the second step of “diggingâ€; the third step will cut one or two spikes or ears from the base of the ear, which is “sweeping the groundâ€. After fruit thinning, depending on the variety and the results of the mother branch size 40-70 grains per ear. The longan eyes using the above methods for fruit thinning have a compact, spherical shape, uniform fruit size, large fruit color, and good commercial quality. They are very popular with consumers and vendors, and their economic value is significantly improved.