Application of cold sterilization technology in packaging and food processing machinery

Consumers' requirements for food are generally safe to eat, stable in nature, and free of additives. In traditional food processing, heat sterilization is mainly used, which leads to destruction of nutrients, increased discoloration, and loss of volatile components. Cold sterilization (physical sterilization) is a new class of modern technology. The physical sterilization conditions are easy to control, and the external environment is less affected. Because the temperature of the food in the sterilization process does not rise or rise very low, it is beneficial to maintain the functional ingredients of the food. The physiological activity is beneficial to maintain color, aroma, taste and nutrients, so the use of cold sterilization technology in the design and manufacture of packaging and food machinery is very necessary.


â– Ultra-high pressure sterilization technology This is a sterilization technology developed in the late 1980s. The food has a good sterilization effect under the pressure of 100-1000 MPa under high pressure. The lethal effect of ultra-high pressure on microorganisms is mainly achieved by destroying the cell wall, coagulating proteins, inhibiting the activity of enzymes and replicating genetic material such as DNA. In general, the higher the pressure, the better the bactericidal effect. Prolonging the compression time at the same pressure does not necessarily improve the sterilization effect. Under the pressure of 400 ~ 600MPa, bacteria, yeasts and molds can be killed, and the bad changes caused by general high temperature sterilization are avoided. The advanced technology of ultra-high pressure "cold sterilization" is high-pressure, normal temperature sterilization, using this technology for food. After the beverage is processed, it not only has high-efficiency bactericidal properties, but also preserves the nutrients in the food and beverage. The product tastes good, the color is natural, the safety is high, and the shelf life is long. This is the advantage that the traditional high-temperature heat sterilization method does not have.
Food ultra-high pressure processing technology is called "a revolution in the food industry", "the world's top ten cutting-edge technology", etc., can be applied to all solid or liquid foods containing liquid ingredients, such as fruits, vegetables, dairy products, eggs. , fish, meat, poultry, juice and soy sauce, vinegar, alcohol, etc. Ultra-high pressure food meets the simple, safe, natural and nutritious consumption needs of new foods in the 21st century. It is believed to have a huge market and broad development prospects.

â– Ultra-high voltage pulse electric field sterilization It is sterilized by the pulse electric field generated by the high-voltage pulser. The alternating action of the electric field and the magnetic field generated by the pulse increases the permeability of the cell membrane, weakens the membrane strength, and finally the membrane is broken, the material in the membrane flows out, the extracellular material infiltrates, and the bacteria body dies. The action of the electromagnetic field produces ionization, which blocks the normal biochemical reaction and metabolism of the cell membrane, and changes the substance in the bacteria. Many researches have been done on this technology at home and abroad, and corresponding treatment devices have been designed to effectively kill dozens of bacteria related to food spoilage. Some manufacturers in France and the United States have used this new technology of electric field to destroy cells, avoiding a series of shortcomings such as protein denaturation and vitamin destruction caused by heating.

â– Strong magnetic pulse sterilization technology This technology uses the biological effect of strong pulse magnetic field to sterilize. On the outside of the infusion tube, a spiral coil is set, and the magnetic pulse generator generates a magnetic field strength of (2~10)T in the coil. When the liquid material passes through the infusion tube, the bacteria therein are killed. The technology has the following characteristics: short sterilization time and high sterilization efficiency. The bactericidal effect is good and the temperature rise is small, which can not only sterilize, but also maintain the original flavor, taste, color, quality and composition (vitamins, amino acids, etc.) of the food. It does not pollute the environment, does not pollute the product, has no noise, is economical and practical, and is an ideal green product. It can be used in a wide range of canned (or packaged) liquid materials such as alcoholic products (beer, yellow wine, low-grade liqueur, various fruit wines, etc.), liquid foods (such as milk, soy milk, fruit and vegetable juice drinks). ) and disinfection of mineral water, purified water, tap water and other drinking water.

â–  Pulsed light sterilization Pulsed light sterilization is a technique that uses a pulsed intense white light method to sterilize. The most basic structure is a power unit and an inert gas lamp unit that supplies energy to the inert gas lamp unit by the power unit so that the inert gas lamp emits light in the ultraviolet to infrared region opposite to the solar spectrum but stronger. Pulsed light uses very short pulses of high intensity white light to kill microorganisms on the surface of the food. The high-intensity white light is similar to sunlight, but is reflected only at a fraction of a second, stronger than sunlight, and kills bacteria quickly. The microbial lethal effect is obvious under pulsed light, and it can be thoroughly sterilized. Different light intensity and time should be controlled for different foods and different strains during operation.

â– Microwave sterilization Microwave is an electromagnetic wave with a frequency from 300MHz to 300GMHz. The process by which microwaves interact directly with materials to convert ultra-high frequency electromagnetic waves into heat. Microwave sterilization is the result of a combination of microwave thermal effects and biological effects. Microwave on the potential distribution of the bacterial membrane section affects the concentration of electrons and ions around the cell membrane, thereby changing the permeability of the cell membrane. The bacteria are therefore malnourished, unable to normal metabolism, and growth and development are hindered to death. From a biochemical point of view, the normal growth and reproduction of nucleic acids (RNA) and deoxyribonucleic acid (DNA) are curly macromolecules that are tightly linked by several hydrogen bonds. Microwaves cause hydrogen bond relaxation, cleavage and recombination, thereby inducing inheritance. Gene or chromosome aberrations, even breaks. Microwave sterilization is the use of electromagnetic field effects and biological effects to kill microorganisms. Practice has proved that the use of microwave devices has obvious advantages in sterilization temperature, sterilization time, product quality maintenance, product shelf life and energy saving.

■ Radiation sterilization Radiation emitted by radioactive isotope usually has three kinds of rays: a, β, and γ, and only gamma rays are used for internal sterilization of food. Γ-ray is a kind of electromagnetic wave with extremely short wavelength, which has strong penetrating power to objects. The cytoplasm of microorganisms is not affected by a structure under certain intensity γ-rays, thus causing variation or death. Nucleic acid metabolism in microbial metabolism can be inhibited by radiation, proteins are denatured by irradiation, and their reproductive functions are most damaged. Radiation does not cause a rise in temperature, so this type of sterilization is called "cold sterilization." Microorganisms are resistant to radiation, and bacteria that are generally resistant to heat are more resistant to radiation, but there are exceptions.

â–  UV sterilization Sunlight can kill bacteria, mainly the role of ultraviolet light. Its sterilization principle is that the microbial molecules are in an unstable state after being excited, thus destroying the unique chemical combination between molecules and causing bacterial death. Microorganisms have different sensitivities to different wavelengths of ultraviolet light, and ultraviolet rays have different lethal doses to different microorganisms. Gram-negative Bacillus sp. is most sensitive to ultraviolet light. The amount of ultraviolet radiation that kills Gram-positive cocci is increased by 5 to 10 times. It is also suitable for the sterilization of air, water, thin-layer fluid products and packaging containers due to its weak UV penetration.

â–  Ozone sterilization Ozone oxidizing power is extremely strong, second only to fluorine, which can rapidly decompose harmful substances. The sterilizing ability is 600 to 3000 times that of chlorine, and it is rapidly reduced to oxygen after decomposition. Ozone technology using its performance has been widely used in developed countries such as Europe, America and Japan. It is the first choice for sterilization, sewage treatment, water purification, food storage, medical disinfection and so on. Medical researchers at the University of Washington in the United States have found that ozone can inhibit the growth of cancer cells; Japan Ishikawajima Hemp Heavy Industry Co., Ltd. has proved that ozone water is expected to be the best biocide for fruit and vegetable, and its bactericidal effect is significantly better than sodium hypochlorite; Chinese Academy of Medical Sciences research proves that ozone It can effectively kill Neisseria gonorrhoeae and decomposes heavy metals in water. The test proves that ozone water is a broad-spectrum fungicide, which can effectively kill common pathogens such as Escherichia coli, wax bacillus, dysentery bacillus, typhoid bacillus, and meningococcus, as well as influenza and hepatitis viruses in a short time. microorganism. It can kill and oxidize fish, meat, fruits and vegetables, various microorganisms on the surface of food, and microorganisms that continue to carry out life activities after leaving the mother body, accelerate mature ethylene gas, extend the shelf life, and wash vegetables and melons with ozone water. Fruits can effectively remove residual pesticides, bacteria, microorganisms and organic matter on the surface, solve the hidden dangers caused by pesticides, and avoid secondary pollution caused by washing and washing fruits and vegetables; can completely kill bacteria in water Eliminate organic matter, purify drinking water, remove odor, odor and decompose heavy metals in water and objects to be washed.

â– Ultrasonic sterilization Ultrasonic waves with a frequency of 9 to 20 kHz/sec or more have a destructive effect on microorganisms. It can cause microbial cell contents to be strongly shaken and destroy cells. It is considered that in an aqueous solution, hydrogen peroxide can be generated due to the action of ultrasonic waves, and it has a germicidal ability. Some people think that when the microbial cell fluid is subjected to high-frequency sound waves, the dissolved gas becomes a small bubble, and the impact of the small bubble can cause the cell to rupture. Therefore, the ultrasonic wave has a certain killing effect on the microorganism.
High-energy ray sterilization technology High-energy ray sterilization is a sterilization method using radiation emitted by radioactive elements CO60 and Cs17 as a source of illumination. The technique used for cold sterilization is ionizing radiation. The radiation will produce direct and indirect effects during the irradiation process; the direct effect is the ionization and chemical action of the microbial interstitial after being irradiated by high-energy electrons; the indirect effect is that the water is generated after receiving the radiation. The ionization acts on other substances in the cell. These two actions block all intracellular activities leading to microbial death. For different strains, controlling different irradiation doses will not damage the color, aroma and taste of the food; there will be no non-food substances remaining, and the sterilization effect is obvious. Therefore, at present, this sterilization technology is mostly used for meat products, fruit preservation and water treatment.

â– Cryogenic conditioning sterilization France has developed this sterilization technology specifically for conditioning dishes. They mix the ingredients in the bag and carry out low-temperature conditioning and sterilization under vacuum, which can avoid the adverse effects on the quality of the finished product caused by multiple heat sterilization. In recent years, Japan has developed a low-temperature inflatable packaging sterilization technology, which can also be applied to certain conditioning foods.

â–  Biological preservation is considered a natural preservation method. Use microorganisms or bacteriocins to control the growth of pathogenic bacteria and the growth of mycotoxins. This is one of the active research and development fields in food biotechnology, and it has great development and application prospects.

â– Active packaging Refers to packaging technology that has special features beyond the performance of conventional packaging. If a component with oxygen absorption is added to the packaging material, the oxygen around the food is eliminated during the shelf life of the packaged food, and the requirements for safe food preservation are achieved. Active packaging is a new packaging concept compared to traditional packaging. It is to change the shelf life of the product by changing the packaging conditions or to improve the safety and sensory properties of the food while maintaining the quality of the food. Active packaging is not only a barrier between the product and the external environment, it combines advanced food packaging and materials science and technology to maximize the quality of packaged food. At present, the active packaging includes the following functions: deoxidation, de-ethylene, removal, release of CO2, humidity control, antibacterial, malabsorption odor, release of ethanol, etc. Many active packagings have been widely used in food, medicine, and daily necessities for storage and transportation.

â– Antibacterial packaging Microorganisms on the surface of food are one of the main factors affecting the shelf life and safety of food. Antibacterial can kill or immediately control the microbes on the surface of food during processing, storage and handling, and extend the shelf life and safety of food. The combination of the packaging material and the preservative, the radiation treatment of the polymer of the packaging material, or the jet of air can provide the package with antibacterial activity.

â– Gate (bar) barrier (obstruction) technology A comprehensive approach that combines the various factors that constrain food preservation. It depends on the food object, and through the necessary treatment, establishes a series of important barriers (barriers) that effectively inhibit the growth of microorganisms and kill them, such as certain moisture, a certain pH, a certain temperature, A certain gas atmosphere, etc., in order to maintain the stability of the food during the shelf life. Some of the traditional Chinese meat products can be stored for a long time without refrigeration, and the principle is also here. The application of modern scientific methods, based on the identification of key factors related to the stability of food preservation, the development of this technology will help to achieve the industrialization of some traditional foods.

â–  Membrane Separation Technology Membrane separation is a molecular-scale separation. The main membrane system is classified into reverse osmosis (RO), nanofiltration (N), ultrafiltration (F), and microfiltration according to the tightness of the membrane pores. (MF). Combining microfiltration technology with chromatographic method and chemical treatment and enzymatic treatment, the various combinations in the milk protein are separated to obtain casein and whey protein. Immunoglobulins can be used to produce advanced infant formula. The use of microwave membranes enables sterility of water and products in the fermentation industry. At present, various liquor companies have widely used 0.45um filter cartridges to replace the original thermal sterilization technology with the terminal filtration of the finished wine, saving energy and avoiding the cooked flavor brought by the high temperature. Fresh draft beer (a beer produced by membrane filtration technology and sterilized under normal temperature conditions) has quickly occupied the market with its excellent quality and taste. In addition, membrane separation technology has been widely used in the desalination of seawater and brackish water, mineral water sterilization, food plant wastewater treatment, and bacterial removal in the air.

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