Preservation technology of the hottest litchi by l

Litchi remote transportation and preservation technology

litchi harvest season is in midsummer, at which time, the temperature often reaches more than 30 ℃. However, litchi has thin pericarp and more juice, which is prone to mechanical damage and microbial infection. At the same time, litchi pericarp is rich in polyphenol oxidase and peroxidase, which are the key enzymes of pericarp browning. When the water loss rate of pericarp reaches about 50% of its own content, browning begins. Therefore, litchi is one of the most difficult fruits to keep fresh. Now the remote cold storage and preservation technology of litchi fresh fruit is introduced as follows for reference

I. color protection treatment

① use litchi color protection agent "gos-l98" (Institute of Botany, Chinese Academy of Sciences), and treat fresh litchi according to its instructions. It can be stored for 7 days under 35 ℃ and 20 days under 5 ℃. Even if the peel is air dried, it still has bright red. ② Soak the fruit in 2% sodium sulfite, 1% citric acid and 2% salt solution for 2 minutes or more. ③ Soak the fruit in 1% citric acid and 2% salt aqueous solution for 2 minutes. The litchi treated by the above 2 and 3 methods can be kept fresh by other fresh-keeping methods for more than 3 days than litchi without color protection treatment

II. Fresh keeping measures

(I) liquid chemical preservation method

its mechanism and requirement is that the drug can form an invisible packaging machine 'target' on the surface of litchi after dissolving in water=_ Blank> transparent film can not only effectively close pores, reduce respiratory intensity, delay fruit aging, but also act as an extender to make it evenly distributed on the whole surface of litchi, and has the effect of antisepsis and sterilization. The commonly used preservatives are:

chlorhexidine is made in China, which is usually 25% suspension. It has the advantages of high efficiency, broad spectrum, low toxicity, low residue, and is harmless to users and consumers. It can effectively prevent and control crown rot, black rot, green mold, and anthrax. After 250 times dilution, it is milky white suspension, which has good suspension, water dispersibility, adhesion and spreadability. China's testing machine has made a benign development. After processing the fruit, the surface is clean, free of stains, and the appearance of the goods is good. Soak it in ice water solution (for precooling, it is required to be below 12 ℃, and 4 ℃ - 6 ℃ is better) for 1 minute, pick it up, quickly blow it dry with an electric fan, then pack it with non-toxic, breathable and water-friendly fresh-keeping film (or ordinary non-toxic polyethylene plastic film), place it in a polystyrene foam box with ice (fruit ice ratio: 1), and load it into a refrigerated car of a train or car or an ordinary truck (covered with tarpaulin) for transportation Marketing

Shibaoke, produced in Germany, is commonly used as 45% emulsifiable concentrate, which has special effects on the prevention and control of a variety of plant diseases caused by ascomycetes and semiotics. Dilute it with double ice water solution and soak it for half a minute, then pick it up. The rest of the treatment is the same as the above 1 method

tektomey made in China, containing thiabendazole 41.8, is a suspension, odorless, tasteless and highly stable. It can be diluted with ice water solution to 300-400 times and soaked for 1 minute. It also has the effect of preventing fruit browning

some domestic fruit preservatives, such as Beijing ZB preservative, Xianbao mango preservative, fangtuo banana preservative, can also be used in experiments

(II) solid preservative preservation method

the principle of sulfur fumigation treatment is that sulfur dioxide gas produced by burning sulfur has the functions of sterilization, bleaching and so on. The SO2 release can be divided into two stages. In the first stage, a higher concentration of SO2 is released within 1-2 days after the packaging of litchi to disinfect the surface of litchi. In the second stage, 0.05-0.1 per 10000 of SO2 can be released for about 2 months to inhibit pathogenic bacteria during long-term storage or long-distance transportation. The disadvantage is that the bleaching effect of SO2 has a certain impact on color protection

activated carbon with strong adsorption can be used as a carrier, adding strong oxidant sodium chlorate, and then adding ferrous sulfate and zinc oxide with fresh-keeping activity. Mix the above four drugs evenly in the dosage of 6:2:1:1, then add a small amount of water to fully mix them, dry them at 100 ℃ - 110 ℃, make them into solid preservatives with a diameter of 2-3 mm, and package the finished products with different specifications and weights as required. Generally, it is put into a small breathable plastic bag (sealed with paper bag externally, or ordinary non-toxic plastic bag. Sometimes, the biological content of RS nylon 10/10 is up to 100%, and some holes are punctured), and then stored with litchi in a foam box (the ice in the box should be wrapped with non-toxic film, and the bag mouth should be tightly tied to prevent ice water from soaking the fruit). This solid preservative can decompose and eliminate harmful gases in the storage process, inhibit the occurrence of mold, and thus play a fresh-keeping role. Its dosage accounts for 2-3% of litchi

(III) fresh keeping bag fresh keeping method

if it is processed with polyolefin resin, the plastic film composite heavy packaging bag with multi-layer structure can reflect more than 95% of the light, so that the temperature in the bag does not rise significantly under direct sunlight. Its moisturizing performance is excellent, and it can adjust the gas composition in the bag by itself, forming a low oxygen and high carbon dioxide fruit storage environment, which can be used in the natural temperature changing environment with the temperature below 60 ℃

III. improve the circulation supporting technology of the North transportation cold chain

adopt a comprehensive fresh-keeping method: through color protection → liquid fresh-keeping → solid fresh-keeping → foam box ice cubes → 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 and a series of treatments, we can achieve planned marketing and see the use of the electro-hydraulic servo universal testing machine. If the storage temperature can be maintained at 4 ℃ - 6 ℃ (relative humidity 75-90%, the same below), it can be kept fresh for one month (the good fruit rate is more than 85%, the same below); The storage temperature 7 can be kept fresh for about 25 days by changing the pendulum and sample base - 8 ℃; The storage temperature is 9-12 ℃, and it can be kept fresh for about 3 weeks. The fresh-keeping temperature of litchi should not be below 4 ℃ to prevent irreversible chilling injury; In large and medium-sized cities, small wholesale fruit merchants or fruit sellers should also have refrigerators to keep fresh. Litchi, which is exported to the north of the Yangtze River, is still transported by the refrigerated truck of the train (maintained at 4 ℃ - 6 ℃), which has good effect and high efficiency. When there is no such car, the impact of the train's open and grate car is also smaller than that of the car's vibration, with a high rate of good fruit and a low total freight