Application of the latest technology in storage an

2022-08-08
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Application of new technology in storage and packaging (Part 1)

I. reduced pressure storage

(I) overview

reduced pressure storage is to place horticultural products in a storage room with excellent air tightness, artificially cause the pressure difference between the storage environment and the internal organization of horticultural products, so that harmful gases in horticultural products can escape quickly, so as to inhibit the respiration of horticultural products and the occurrence of various diseases, and extend the storage life of horticultural products

the main measures are to reduce air pressure, cooperate with low temperature and high humidity, and use low-pressure air for circulation, so as to create a favorable storage environment for horticultural products. The low pressure in the storage room is generated by the vacuum pump pumping out the indoor air. The low pressure is controlled below 100mm Hg, and the minimum is 8mm Hg. The relative humidity in the air is controlled by the indoor humidifier, which is generally more than 90%. This method reduces the indoor oxygen content during air extraction, keeps the respiration of horticultural products at the lowest level, and also eliminates some indoor harmful gases such as oxygen, carbon dioxide, ethylene, ethanol, acetaldehyde, etc., which is conducive to the long-term storage of horticultural products

(II) case

1. The storage and preservation of sweet cherries under reduced pressure is known as the "third revolution" in the storage and preservation of horticultural products. Sweet cherry is a kind of fruit with early ripening period, but its ripening period is short and it is not storable. The shelf life after storage is usually only 1 ~ 2 days. The national fresh-keeping center cooperated with the Agricultural Technology Extension Center of Lushunkou District in Dalian to carry out pilot tests and demonstrations, and made new breakthroughs. The sweet cherries have been stored for 40 days, and have been sold on the market with good response

2. Because the peel of winter jujube is thin, the pulp is crisp and tender, and the water content is high, it can only be kept fresh for 6 to 7 days at room temperature after harvest. In the future, it will soon lose water, wilt, soften, wine (the pulp has a wine taste) and rot, losing its commodity value

put the pre cooled jujube fruit into the decompression stack, control the temperature at -2 ℃± 0.5 ℃, keep the relative humidity above 95%, and control the vacuum degree at 1/5 ~ 1/4 atmospheric pressure (20..3313kpa). At this time, the oxygen concentration reaches 4% - 8%, and the oxygen concentration of this facility can be reduced to 4% (2) attapulgite clay (at or ATP) within 0.5h. The storage period of winter jujube can reach 100 days, and the fresh-keeping crispy fruit rate can reach more than 90%, ranking the international leading level

II. Radiation storage

(I) overview

radiation storage is the use of radiation sources such as cobalt 60 to irradiate horticultural products, which can inhibit bud sterilization, delay fruit ripening and aging, and thus extend the storage life of horticultural products

radiation is a new technology for preserving horticultural products, which has developed rapidly. Radiation can not only interfere with the basic metabolic process, delay the ripening and aging of fruits, but also kill insects, sterilize and disinfect, and reduce the fruit decay caused by pests and microorganisms. At present, three kinds of radiation sources have been used in the world, namely, radiation sources (gamma rays of cobalt 60 and cesium 137), accelerated electrons and X-rays converted by accelerated electrons. They only cause chemical changes in the molecules of horticultural products, and there is no radioactive residue, so the preservation technology is safe. Too small radiation dose can not play the role of sterilization and preservation, and too large dose may accelerate the aging of horticultural products. Different horticultural production 1. Transmission system of tensile testing machine: it is very critical to select the appropriate dose of products. Generally, 1000 ~ 3000gy irradiation is used

(II) case

1. 60Co for Strawberry γ The storage period of strawberry berries irradiated with X-ray at a dose of 1500 ~ 2000gy is 2 ~ 3 times longer than that of untreated berries at room temperature or under the condition of rapid rise storage of cold conditioning speed valve. The storage period can reach 40d under 0 ~ 1 ℃. The main reason is to kill the gray mold, Rhizopus and Mucor that cause strawberry fruit corruption. Irradiation had no effect on the nutritional components of strawberry. The effect is better if the moist heat treatment (41 ~ 50 ℃) is carried out before irradiation

2. After removing impurities, mushroom is put into ordinary polyethylene plastic bag, and 60Co γ Irradiation with a dose of 1000gy, and then placed in 0 ℃ cold storage. After one month storage, the effect is good, the weight does not decrease, and the commodity value does not decrease

III. preservative treatment

(I) overview

preservative is the use of antioxidants, preservatives and coating agents to treat horticultural products, effectively reduce their respiratory intensity, reduce water loss, and extend the storage life of horticultural products

it can be divided into adsorption type, protective type and natural type. It is mainly used as an auxiliary fresh-keeping means combined with cold storage, and is applied to the batch and family style fresh-keeping market

adsorption preservatives mainly include oxygen getter, ethylene absorbent and carbon dioxide adsorbent. For example, ethylene adsorbent is generally composed of zeolite, aluminum, calcium peroxide, potassium permanganate, etc., which can control the content of exogenous ethylene and eliminate the self catalysis of ethylene

protective preservatives mainly include carbendazim, bacteriostasis, sorbic acid and its salts, ammonia chloride and sodium sulfate at the end of the mountain experiment. Its main function is to prevent pathogenic microorganisms from invading the fruit and kill microorganisms on the surface of the fruit

the main component of natural preservative is inositol hexaphosphate, which is extracted from the by-product of grain seed processing, and acts on fruits and vegetables through coating or impregnation. It has a good antioxidant effect and prevents the freshness of fruits and vegetables from decreasing due to oxidation; It can effectively chelate iron, zinc and other metal ions on the surface of fruits and vegetables, make them lose their catalytic properties, and delay the deterioration of the color of fruits and vegetables; It can close the pores of the epidermis of fruits and vegetables, inhibit the vigorous respiration of fruits, reduce water loss, resist the invasion of external bacteria and inhibit the reproduction of fungi; Prevent the oxidation of ascorbic acid and maintain the nutrients of fruits and vegetables

storage, transportation and preservation of fruits and vegetables will be an important link in the development of fruits and vegetables in the future, and will gradually receive attention from all aspects. The storage and preservation of fruits and vegetables will change from bulk fruits and vegetables to the diversification of varieties, especially some rare fruits and vegetables will become the hot spot of preservation in the future. In addition, China is rich in wild fruits and vegetables with high nutritional value. With the development of food science and the change of people's dietary concept, it will also arouse social interest. Some newer and better comprehensive preservation methods will continue to emerge and become the mainstream

(II) case

1. New plastic fresh-keeping film Japan has successfully developed a new disposable plastic fresh-keeping film. It is made of two layers of nylon semi packer 'target with excellent water permeability=_ Blank> it is composed of transparent membrane, and sugar syrup with high osmotic pressure is installed between the two layers. Using this plastic film to package fruits and vegetables can slowly absorb the water exuding from the surface of fruits and vegetables, so as to achieve the purpose of fresh-keeping

2. hydrocarbon mixture preservation method this is a "Natural Edible Preservative" developed by a British Semper biotechnology company, which can prolong the storage life of tomatoes, peppers, pears, grapes and other fruits and vegetables by one time. It uses a complex mixture of hydrocarbons. When in use, dissolve it in water to form a solution, and then soak the fruits and vegetables to be preserved in the solution, so that the surface of the fruits and vegetables is evenly coated with a layer of liquid agent. In this way, the absorption of oxygen is greatly reduced, and the carbon dioxide produced by fruits and vegetables is almost discharged. Therefore, the effect of preservatives is similar to that of "anesthetics" applied to fruits and vegetables, making them in a dormant state

3. citrus preservative paper citrus preservative paper is a kind of thin special paper. It is composed of fibers, soft texture, and has a certain elasticity, which is a good protective film for fruits. Antiseptic fresh-keeping paper is to add chemical drugs to the paper fiber or coat the chemical drugs on the paper surface. After wrapping the fruit with it, it can kill all kinds of bacteria on the fruit surface and control the infection of stem rot, black rot and other bacteria. Using antiseptic fresh-keeping paper for single fruit packaging storage can make the ratio of O2 and CO2 concentration in the small space where the fruit can survive. Because the fruit's own respiration regulates the concentration of O2 and CO2 in the storage environment, that is, O2 concentration gradually decreases and CO2 concentration gradually increases, thus inhibiting the respiration of the fruit and enhancing the storage resistance of the fruit. In addition, the preservative paper also plays a role in inhibiting water evaporation, thus maintaining the weight and freshness of fruits

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