Application of innovative storage and preservation

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Application of innovative storage and preservation technology of fruits (II)

2 radiation storage

this method uses 60Co γ Radiation storage of fruits and vegetables is carried out based on the principle that rays have strong penetration ability. Although the bactericidal effect of X-rays had been discovered as early as the 19th century, the research on the treatment and preservation of food with radiation as atomic energy for industrial and agricultural production actually began in the 1940s. Over the past 40 years, many countries, including China, have carried out extensive research in this area and made great progress; For some food production areas, by 1976, 18 countries had given "unconditional approval" to 25 kinds of radiation treated foods, which can be sold as commodities, including potatoes, onions, garlic, mushrooms, asparagus, dried fruits. Let's learn about the relevant knowledge of changing the testing machine. Fresh fruits and other vegetables and fruits

at present, countries mainly use 60 cobalt or 137 cesium as the radiation source of Ding ray irradiation in radiation preserved food, and also use electron rays with energy below 10MeV. γ X-ray is a kind of electromagnetic ray with strong penetration. When it passes through the living body, it will make the water and other substances in the body have electromagnetic effect, producing free radicals or ions, thus affecting the new and old radiation process of the body, and in serious cases, it will kill cells. Due to different doses during irradiation, the effects are also different:

low dose: below 100krad. It affects plant generation, inhibits the germination of tubers and bulbs, and kills parasites

medium dose: 100---1000krad, inhibit the generation of radiation, prolong the storage period of fruits and vegetables, prevent fungal activities, and kill Salmonella

high dose: above 1000krad, thoroughly sterilized

in vegetable storage, use γ The inhibition of tuber and bulb germination by X-ray irradiation has been studied for a long time, and the effect is obvious. Some countries have approved it to be used in production, and the irradiation dose is about 5000-15000r. According to the research of horticulture Institute of Shanghai Academy of Agricultural Sciences, ginger irradiation 2000r has a good effect on bud inhibition, and too high dose will cause rot. γ Radiation can also inhibit mushroom film breaking and umbrella opening. According to the data of South China Agricultural University, the effective dose is 50---70kr, and the umbrella will not be opened within 5 days after irradiation. The effect of radiation treatment on Inhibiting Germination is mainly low dose γ Radiation can affect the metabolism of nucleic acids in meristem. In the inner buds of irradiated onions, RNA and DNA were lower than those of the control; At the beginning of growth, the synthesis of soluble RNA in irradiated inner buds was particularly inhibited, so the growth was inhibited

however, little research has been done on the radiation treatment of other vegetables and fruits. According to foreign reports, some fruits can have a certain preservative effect after being irradiated with 200-250krad; However, some of them showed serious injury symptoms after storage for a period of time and were infected with toxic bacteria; Pear and nectarine seem to have ripening effect after irradiation. It is reported that tomatoes treated with low dose do not show ripening effect. Irradiation of 7-10krad has preservative effect and prolongs the storage period by 4-12 days; When the dosage is 200-400krad, the ripening can be delayed, but it will lead to bad smell. At present, the maximum dose used for fruits and vegetables abroad is 500krad. In China, in recent years, some units' experiments on fruits and vegetables have also achieved gratifying results. Harbin Institute of food industry, etc. (1974) radiated 5---50kr to green pepper, which had a certain effect of inhibiting ripening, and the fruit stalk kept green better. Some units irradiated cucumbers with different doses (3-30kr) and dose rates (as low as 10kr/min) to inhibit ripening and aging and stop seed development. Shenyang Agricultural University et al. (1978) irradiated tomatoes (a strain of Qingdao Zaohong) with a dose rate of 236r/min for 6-200kr, and found that all doses had the effect of inhibiting ripening, and the more efficient the dose, the more obvious it should be; But at the same time, we can see that radiation treatment causes browning disease of fruit surface strip depression similar to "tiger skin disease", especially those above 10kr. through γ It's easy to get rid of it Γ--- In the 190-380kr group, all the liverworts were etiolated, and the tissues died. In the 95kr group, the development of the liverwort bracts was inhibited, and the liverwort stems faded slightly. In the control group, the liverwort bracts also took off green slightly, and the development of the liverwort bracts expanded (Shenyang Agricultural University, 1978). Various reports also pointed out that the radiation effect is not only related to the radiation dose, but also positively related to the dose rate

radiation treatment may cause food discoloration and taste change, which is frequently reported at home and abroad, and it is common to cause browning of fresh fruits and vegetables. Lizhicheng (1985) observed that the decay loss of tomatoes, green peppers, cucumbers, garlic moss and other vegetables increased after radiation treatment, and believed that radiation might cause physiological damage and weaken the original disease resistance of products. Therefore, whether radiation can play the role of corrosion prevention and preservation should be considered: ① the sensitivity of various products and their main decay bacteria to radiation; ② Whether the main rot pathogen can infect repeatedly and its pathogenic law and time. In order to avoid radiation injury, fresh fruits and vegetables can only be exposed to low doses and dose rates, and attention should be paid to species, variety selection and storage management measures after treatment

both at home and abroad attach great importance to the safety and health of radiation preserved food. According to a large number of experimental materials and theoretical analysis, radioactive food is safe and harmless, but in order to ensure the health of the people, various experimental analysis should be carried out separately for each kind of radioactive food, including animal tests for many generations. Only after it is confirmed to be safe and harmless, can it be approved by the government in the form of law for commodity production

3 coating storage

coating storage is a simple storage method by coating a film on the peel to cover the pores on the peel, which can reduce water loss and inhibit gas exchange in a certain period of time. Sometimes, preservatives (preservatives) are added to the waxing to prevent bacterial infection. At the same time, it can increase the luster of the fruit surface and improve the value of goods. This method is generally combined with appropriate cooling effect. In fruit areas with high temperature, high humidity and serious diseases and pests, the effect is poor. At present, domestic preservatives are mostly fungicides in pesticides. Therefore, be careful in production and use to avoid polluting fruits and vegetables or causing economic losses

4 ozone storage

is a method of applying ozone gas to cold storage for fresh storage of fruits and vegetables. Worldwide, ozone has been used in cold storage for nearly a century. In 1909, France debotti refrigeration plant used ozone to sterilize cooled meat. In 1928, Americans established a "Heji egg factory" in Tianjin, and its egg beating room was disinfected with ozone. In China, the application of ozone in cold storage started late. With the improvement of ozone generator manufacturing technology, ozone is more and more widely used in cold storage

ozone is an isomer of oxygen, with the molecular formula of O3. It is the same as the constituent elements of oxygen O2, with different forms and properties. Chemical properties of ozone: with strong oxidation energy, Jinan assaying Dutch customer signing power, under standard pressure and temperature; The solubility in water is 13 times that of oxygen, which is 1.658 times that of air. Ozone is very unstable and easy to decompose into O2. Through its strong oxidation, it can be used for sterilization, disinfection, deodorization and preservation in cold storage. Because ozone is unstable, it is more beneficial to use it in cold storage to assist in storage and preservation, because the final product of its decomposition is oxygen, which will not leave harmful residues in the stored food and fruits. According to the research of Tsinghua University, there are three aspects of ozone in cold storage. The machine industry should make a breakthrough in non-contact deformation measurement technology and automatic deformation measurement technology as soon as possible. The mechanism is: first, kill microorganisms, disinfect and sterilize; Second, oxidize and deodorize all kinds of smelly organic and inorganic substances; Third, the products of metabolism are oxidized, so as to inhibit the metabolic process and play a role in keeping quality and freshness

according to the physical and chemical properties of ozone, it is effective to use ozone for fresh keeping. Someone tried to install the self-made or purchased ozone generator on the wall of the storage room 2 meters away from the ground, turn on the machine for 1-2 hours every day, try to close the door, maintain and increase the ozone concentration to 12-22 mg/kg, and control the indoor humidity at about 95%. In the case of high humidity, the sterilization and fresh-keeping effect can be greatly improved

(to be 5. Take cushion blocks with corresponding shapes for test pieces with complex shapes (Continued)

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