Fourth, low-temperature refrigeration and anti-mold rot packaging technology low-temperature refrigeration anti-mold rot packaging technology is controlled by the temperature of the commodity itself, so that it is lower than the minimum limit of growth and reproduction of moldy humic microorganisms, control of enzyme activity. On the one hand, it inhibits the respiratory oxidation process of biological products, causing their own decomposition to be obstructed. Once the temperature is restored, it can still maintain its original quality; on the other hand, it inhibits the metabolism and growth and reproduction of moldy rot microorganisms to achieve anti-corruption. purpose.
The temperature and time required for cold storage and mildew prevention should be based on the specific commodity. In general, the lower the temperature and the longer the duration, the higher the mortality of moldy rot microbes. According to the level of refrigeration temperature and the length of time, it can be divided into cold storage and frozen storage. The refrigerated anti-mold and rot-proof packaging is suitable for perishable goods with large water content and impermeability to freezing, and is stored at a temperature of about 0° C. for a short time, such as vegetables, fruits, and fresh eggs. During the cold storage, the enzymes of the moldy microorganisms almost lost their activity. The various physiological and biochemical reactions of the metabolism were slow and even stopped. The growth and reproduction were inhibited, but they did not die. Frozen storage is suitable for freeze-tolerant perishable products with high moisture content and is stored for a long time at about -16--18°C, such as meat and fish.
During the frozen storage period, the quality of the product is basically not impaired, and the moldy rot microbes and the intracellular water become ice crystals dehydrated. The ice crystal water damages the plasma membrane and causes death and injury. Low-temperature storage and mildew packaging should be made of low-temperature-resistant packaging materials.
Fifth, dry anti-mold rot packaging technology Microbiological living environment lack of moisture that causes dry, in the dry conditions, mold can not reproduce, the product will not rot.
Dry and mold-repellent packaging technology is to reduce the moisture in the sealed package and the water content of the product itself, so that the mold and rot microorganisms can not obtain the water needed for growth and reproduction to achieve the purpose of preventing mold and rot. Because drying can denature microbial cell proteins and increase the concentration of salts, so that microbial growth is inhibited or prompted to die. The ability of mold mycelium to resist drying is very weak, especially young strains have a weak ability to resist drying. A certain amount of desiccant can be contained in the sealed package to absorb the moisture in the package, so that the moisture content of the contained product can be reduced below the allowable moisture content.
In general, high water loss is not easy to cause the death of microorganisms; slow drying of mold cells is the most common death, and it is the fastest in the early drying period. Bacteria are not easy to die when they are dried at low temperatures, and they are most likely to die at room temperature after drying.
VI, ionizing radiation anti-mold rot packaging technology energy through the space called radiation, radiation to the irradiated material to produce ionization, known as ionizing radiation.
The direct effect of ionizing radiation is that when the radiation passes through the microorganisms, the internal components of the microorganism can be decomposed to induce mutation or death. Its indirect effect is to dissociate water molecules into free radicals, and radicals react with dissolved oxygen in the liquid to produce strong oxidizing groups. This group oxidizes the -SH group of the microbial enzyme protein and the enzyme loses its activity, thus making it mutagenic or death.
Ionizing radiation is generally the alpha, beta, and gamma rays released by radioactive isotopes. Both of them can damage certain parts of the microbial cell structure and metabolism. Alpha rays are absorbed by air at the time of irradiation and hardly reach the target. The beta-ray penetration is weak and is limited to surface sterilization. Gamma ray penetration is strong and can be used for internal sterilization of foods. The radiation can kill insects, and the radiation will not cause the object to heat up, so it can be called cold sterilization. However, some foods may deteriorate or improve their quality after being irradiated.
Ionizing radiation anti-mold rot packaging is currently used mainly for beta ray and gamma ray. After the ionized radiation is applied to the packaged goods, it completes the function of sterilizing and sterilizing. After irradiation, if it is no longer contaminated, it will cooperate with the conditions of cold storage; low dose radiation energy. Extended shelf life weeks to months. High-dose radiation can be completely sterilized and stored for long periods of time.
7. Ultraviolet, microwave, far-infrared and high-frequency electric fields Ultraviolet ultraviolet light is also a bactericidal effect of rays, which is the main factor in solar sterilization. The wavelength range of ultraviolet rays is 100-400nm, among them the ultraviolet ray with the wavelength of 200-300nm has bactericidal action, especially 265-266nm bactericidal force is the strongest. Ultraviolet light penetrating power is very weak, so it can only kill the humic microorganisms on the surface of the commodity. In addition, foods containing fats or proteins can cause odors or discoloration when exposed to ultraviolet light, and sterilization by ultraviolet radiation should not be used.
Ultraviolet light is generally used to process packaging containers (or materials) and non-food items that are packaged. These objects to be sterilized are irradiated with ultraviolet rays for a certain period of time to kill the mold and rot microbes on the surfaces of the products and the containers. Prepackaging can extend the shelf life.
Microwave microwaves are high-frequency electromagnetic waves with a frequency of 300-300000 MHz. An object that has a lot of water and fat content can easily absorb microwave energy and convert it into heat energy after absorption. The sterilization mechanism of microwaves is that microorganisms absorb microwave energy and then transform it into heat on the one hand and bactericidal. On the other hand, moisture and fat and other substances of cells are affected by microwaves, and their molecules vibrate and vibrate. The heat generated by the internal damage of the cells causes the death of the cells. The heat energy generated by the microwave is in the interior, so the utilization of heat energy is high, the heating time is short, and heating is even.
Far-infrared far-infrared is an electromagnetic wave with a frequency higher than 3000000 MHz. Its function is similar to that of microwaves. Its bactericidal mechanism is mainly the radiation of far-infrared rays and the resulting high temperatures that cause the bacteria to rapidly dehydrate and dry and die.
The sterilizing mechanism of high-frequency electric field high-frequency electric field is that the commodities with high moisture content and microorganisms can “absorb†the frequency energy of the electric energy into heat energy and sterilize. As long as the microorganisms on the commodities and commodities have sufficient moisture and a high-frequency electric field with a certain intensity, disinfection can be completed in an instant.
Commodity anti-mold rot packaging technology (2)
December 28 03:07:33, 2023
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