Main technical measures for preservation and trans

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The main technical measures for the preservation and transportation of longan

1. Pre harvest treatment can be spray on longan trees with chlorhexidine or 0.02% 2,4-D solution, or both, which can prolong the storage time of longan after harvest. Generally, it can be sprayed about 2 weeks before mining

2. Longan harvested in due time for transportation to the north can be harvested in 8.2-8.8. Longan whose international influence in China's plastic machinery industry is increasing should stay until 8 The fruit should be harvested before 10 a.m. on sunny or cloudy days to improve the content of sugar, amino acids and vitamins. When picking the fruit, use the fruit scissors to cut off the lower compound leaves at the base of the ear, so as not to damage the tree body. Pick and place the fruit gently to avoid mechanical damage

3. Color protection treatment can be combined with fruit washing. Grading shall be carried out before treatment to remove rotten, cracked, damaged and pest fruits. According to the requirements of the fruit manufacturer, one of the following methods can be selected for color protection:

(1) 0.5% citric acid plus 0.03% vitamin C solution, or 1% citric acid solution for 2 minutes

(2) soak the fruit in 2% sodium sulfite, 1% citric acid and 2% salt solution for 2 minutes

4. Preservation treatment

(1) the mechanism of liquid chemical preservation method is that the agent can quickly form a 'target' on the surface of longan fruit after dissolving in water=_ Blank> transparent membrane can not only effectively close stomata, reduce respiratory intensity, delay fruit aging, but also play a role in antisepsis and sterilization. The commonly used preservatives and preservation methods are as follows: a. tekto. It is a glue suspension, tasteless, odorless and highly stable. It is effective against Penicillium, green mold, wood mold, gray mold, sickle mold, black stalk rot, brown stalk rot and anthrax. Use ice water (below 12 ℃, ℃ is better) to dilute the medicine solution and soak the fruit for 1 minute. B. Chlorhydrin. It is a new generation of contact bactericide, which can effectively control crown rot, black rot, Penicillium, green mold, green mold and anthrax. It has the advantages of high efficiency, low toxicity, low residue and safety to users and consumers. After 250 times of release, it is milky white suspension with good suspension, adhesion and adhesion. It can be used to soak fruit for 1 minute. C. Tecdol is mixed with chlorphenamine. Mix 0.02%ga3 with 0.1% terketol and Chlorphenamine to soak the fruit for 1 minute. After the above treatment, the fruits are dried by electric fan or cool dry after waterlogging, and then packaged with non-toxic, breathable and permeable fresh-keeping film. They are placed in a polystyrene foam box filled with ice cubes (fruit ice ratio: 1) into the oil tank of the universal tensile testing machine. The special fresh-keeping composite packaging bags and bamboo baskets made of polyolefin resin are used outside the box, which is more suitable for long-distance transportation

(2) solid preservative preservation method

① sulfur fumigation treatment produces sulfur dioxide gas from burning sulfur to achieve sterilization and bleaching. The dosage of domestic sulfur dioxide fresh-keeping tablets (0.62g per tablet) is about 0.25% of the fruit weight, that is, the practical fresh-keeping tablets per kilogram of longan fruit are placed on the bottom and upper layers of the packaged fruit

② 0.1ml per kilogram of longan fruit is fumigated with clotrimycin. The solution can be absorbed with rags, and then placed in a plastic bag with longan, and the bag mouth is fastened

③ the amount of SEC butylamine fumigated in the whole cluster of longan with branches per kilogram was 0.15ml. Put the longan fruit in 0 In the 06mm thick polyethylene film bag, conduct 24-hour sealed fumigation. After fumigation, open the bag and exhaust, and then refrigerate, store and transport

④ the newly increased production capacity is small, and the Chinese herbal medicine coated fresh-keeping paper is made of traditional Chinese medicine powder made of Stemona, Polygonum cuspidatum and galangal with licorice, and then mixed with oxidized starch. It is used to pack longan and keep it fresh at room temperature (southern summer) for 8 days, with a good fruit rate of more than 91%; If it is stored and transported at low temperature (temperature ℃, relative humidity%) for one month, the good fruit rate is about 95%, the fruit color is good, and the flavor changes little. The preparation method of Chinese herbal medicine coated fresh-keeping paper is as follows: weigh 350g Baibu, 300g Polygonum cuspidatum, 500g galangal and 100g licorice, and use a grinder to crush and SIFT (more than 40 mesh) into powder; Take 200g of starch, 1.2g of potassium permanganate, 1.5g of borax, 1g of sodium hydroxide and 100ml of water, heat them to ℃, keep stirring for minutes, and then cool them to become oxidized starch solution. The Chinese herbal medicine powder and oxidized starch solution are mixed in a ratio of 1:2, and then evenly coated on ordinary packaging paper, dried on a dryer or stove (℃), and then made into packaging paper or packaging bags of different specifications as required, stacked into bundles, And then packed with non-toxic plastic film

(3) fresh keeping bag fresh keeping method using medical high molecular materials, it gradually becomes a multi-layer plastic film composite heavy packaging bag made of polyolefin resin, which is the most widely used and used material. It can reflect more than 95% of the light, so that the temperature in the bag does not rise significantly under direct sunlight, and its moisturizing performance is excellent, and it can form a low oxygen and high carbon dioxide storage environment in the bag

5. Supporting technology of cold chain for longan transportation to North China longan adopts a series of comprehensive fresh-keeping methods, such as color protection → liquid fresh-keeping → solid fresh-keeping → foam cream plus ice → special fresh-keeping bags outside the box → bamboo baskets or wooden crates outside the bag → cold storage or controlled atmosphere storage in the wholesale market, so as to achieve planned marketing. If the cold storage temperature is maintained at ℃ (relative humidity%, the same below), the good fruit rate is about 97% after storage for 1 month; The rate of good fruit was still about 93% when the temperature of cold storage was kept at ℃ for 21 days. Longan should not be stored below 1 ℃ at low temperature to prevent chilling injury. Small batch fruit vendors and fruit merchants in large and medium-sized cities should have freezer facilities; It is exported to the northeast, northwest and North China. The refrigerated vehicle of train (maintaining ℃) has good transportation effect, high rate of good fruit and great benefit. The open (grid) wagon of the train is also faster than the automobile transportation, the fruit is less affected by vibration and resonance, the good fruit rate is high, and the moving cost is still low

(source: China Agriculture)

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