Consumers' requirements for foods are generally safe to eat, stable, and without additives. In the traditional food processing, heat sterilization is mainly used, resulting in destruction of nutrients, increased discoloration, and loss of volatile components. Cold sterilization (physical sterilization) is a new type of contemporary technology. The physical sterilization conditions are easy to control and the external environmental impact is small. Since 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 also conducive to maintaining the color, fragrance, taste and nutrient content. Therefore, it is necessary to adopt cold sterilization technology for the design and manufacture of packaging and food machinery.
Ultra-high pressure sterilization technology This is a sterilization technology developed at the end of the 1980s. The food has good sterilization effect under ultra-high pressure of 100 to 1000 MPa. The lethal effect of ultra high pressure on microorganisms is mainly achieved by destroying its cell walls, coagulating proteins, inhibiting the activity of enzymes, and copying 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 increase the sterilization effect. Under the pressure of 400-600 MPa, bacteria, yeasts and molds can be killed to avoid adverse changes caused by general high temperature sterilization. The advanced technology of ultra-high pressure "cold sterilization" is high pressure and room temperature sterilization. This technology is applied to foods. After the beverage is processed, it not only possesses high bactericidal efficiency, but also retains the nutrients in the food and beverage intact. The product has good taste, natural color, high safety, and long shelf life, which are advantages that traditional high-temperature heat sterilization methods do not have.
The food ultra-high pressure processing technology is called “a revolution in the food industry†and “the top ten cutting-edge technologies in the world today†and can be applied to all solid or liquid foods containing liquid ingredients such as fruits, vegetables, dairy products, and eggs. , fish, meat, poultry, fruit juices, soy sauce, vinegar, alcohol, etc. Ultrahigh-pressure foods meet the simple, safe, natural and nutritious consumer demand for new foods in the 21st century. It is believed that it has huge market potential and broad development prospects.
It is sterilized by the pulsed electric field generated by the high-voltage pulser. The alternating action of the electric and magnetic fields generated by the pulse increases the permeability of the cell membrane, weakens the membrane strength, eventually ruptures the membrane, causes membrane outflow, extramembrane material infiltration, and bacterial death. The role of electromagnetic fields, resulting in ionization, blocking the normal biochemical reactions and metabolism of the cell membrane, so that the substance in the bacteria change. Many researches have been done on this technology at home and abroad, and corresponding processing devices have been designed to effectively kill dozens of bacteria related to food corruption. Some manufacturers in France and the United States have used this new technology to destroy cells in practice, avoiding a series of shortcomings such as protein denaturation and vitamin damage caused by heating.
Strong Magnetic Pulse Sterilization Technology This technology uses the biological effect of a strong pulsed magnetic field to sterilize. Outside the infusion tube, a spiral type coil is set. The magnetic pulse generator generates a magnetic field intensity of (2 to 10)T within the coil. When the liquid material passes through the section of the infusion tube, the bacteria therein are killed. The technology has the following characteristics: short sterilization time and high sterilization efficiency. Good bactericidal effect and small temperature rise can achieve both sterilization, but also can maintain the original flavor, taste, color, quality and composition of the food (vitamins, amino acids, etc.) unchanged. It is an ideal green product that does not pollute the environment, does not pollute the product, is noiseless, economical and practical. Wide application range, can be used for various canned (or packaged) pre-liquid materials such as alcoholic products (beer, rice wine, low-alcohol liquor, various fruit wines, etc.), liquid foods (such as milk, soy milk, fruit and vegetable juice drinks ) As well as the disinfection and sterilization of mineral water, purified water, tap water and other drinking water.
Pulsed light bactericidal pulsed light sterilizing is a technique that sterilizes using a pulsed intense white flash method. Its most basic structure is a power unit and an inert gas lamp unit. The power unit provides energy to the inert gas lamp unit so that the inert gas lamp emits light in the ultraviolet-to-infrared region which is opposite to the solar spectrum, but has stronger intensity for sterilization. Pulsed light uses extremely short pulses of high-intensity white light to kill microbes on the surface of food. The high-intensity white light resembles sunlight, but it reflects only at a fraction of a second. It is stronger than sunlight and can kill bacteria quickly. Under the pulse of strong light to microbial lethal effect, can be used for thorough sterilization. In the operation of different foods, different strains, need to control the different light intensity and time.
Microwave sterilization Microwaves are electromagnetic waves with frequencies from 300MHz to 300GMHz. The direct interaction between microwaves and materials transforms UHF electromagnetic waves into heat energy. Microwave sterilization is the result of a combination of microwave thermal effects and biological effects. The potential distribution of microwaves on the cross-section of the bacterial membrane affects the concentration of electrons and ions around the cell membrane, thereby altering the permeability of the cell membrane. As a result, the bacteria are malnourished, cannot be metabolized normally, and growth is hindered to death. From a biochemical point of view, nucleic acids (RNAs) and deoxyribonucleic acids (DNAs) that bacteria normally grow and multiply are crimped macromolecules that are tightly linked by several hydrogen bonds. Microwaves cause hydrogen bonds to relax, break, and recombine, thereby inducing inheritance. Gene or chromosomal aberrations, even breaks. Microwave sterilization is the use of electromagnetic field effects and biological effects play a role in the killing of microorganisms. Practice has proved that using microwave devices has obvious advantages in sterilization temperature, sterilization time, product quality maintenance, product shelf life and energy saving.
Radiation Radiation Sterilization Radiation The isotope radiation is usually a, β, and γ, and only gamma rays are used to sterilize foods. Γ-rays are electromagnetic waves of very short wavelengths and have a strong penetration of objects. Under the gamma ray of a certain intensity, no cytoplasm of microorganisms is affected, resulting in mutation or death. The metabolism of nucleic acid in microbial metabolism can be inhibited by radiation, and the protein undergoes degeneration due to irradiation, and its reproductive function is most damaged. Irradiation does not cause temperature rise, so this sterilization method is called "cold sterilization." The resistance of microorganisms to radiation, and bacteria that are generally resistant to heat, are also relatively resistant to radiation, but there are exceptions.
UV sterilization of sunlight can kill bacteria, mainly the role of ultraviolet light. The principle of its sterilization is that microorganism molecules are in an unstable state after being stimulated, thereby destroying the unique chemical combination between molecules and causing the death of bacteria. Microorganisms have different sensitivities to different wavelengths of ultraviolet light, and ultraviolet radiation has different lethal doses to different microorganisms. Gram-negative bacillus-free bacteria are most sensitive to ultraviolet light. The amount of UV radiation that kills Gram-positive cocci must be increased by 5 to 10 times. Due to weak UV penetration, it is suitable for the sterilization of air, water, thin fluid products and packaging containers.
Ozone sterilization ozone oxidizing power is very strong, second only to fluorine, can quickly decompose harmful substances, bactericidal capacity is 600 to 3000 times that of chlorine, after its decomposition quickly reduced to oxygen. Utilizing its performance of ozone technology has long been widely used in Europe and the United States, Japan and other developed countries, is the preferred technology for disinfection and disinfection, sewage treatment, water purification, food storage, medical disinfection and other aspects. University of Washington medical researchers found that ozone can inhibit the growth of cancer cells; Japan's Ishikawajima Heavy Industries Co., Ltd. proved that ozone water is expected to become the best fruit and vegetable fungicide, the bactericidal effect is significantly better than sodium hypochlorite; Chinese Academy of Medical Sciences research shows that ozone Can effectively kill Neisseria gonorrhoeae, and the decomposition of heavy metals in the water. The test proves that ozone water is a broad-spectrum fungicide that can effectively kill the common pathogens such as Escherichia coli, wax bacillus, dysentery bacillus, typhoid bacillus, and diclocococcus, as well as flu germs and hepatitis viruses in a short period of time. microorganism. It can kill and oxidize fish, meat, fruits and vegetables, various microorganisms on the surface of the food that can produce mutations, and microorganisms that continue to carry out life activities after the fruits and vegetables are detached from the mother's body, accelerate the mature ethylene gas, extend the preservation period, and wash the vegetable melon with ozone water As a result, it can effectively remove residual pesticides, bacteria, microorganisms and organic matter on the surface, solve the hidden dangers caused by pesticides, and at the same time avoid the secondary pollution caused by washing and washing fruits and vegetables; it can completely kill bacteria in water. , Eliminate organic matter, purify drinking water, remove odors, odors, and decompose heavy metals in water and objects to be cleaned.
Ultrasonic sterilizing ultrasonic waves with a frequency of 9 to 20 kilohertz/s may damage the microorganisms. It can make the contents of microbial cells subject to strong shocks and destroy the cells. It is generally believed that in the aqueous solution, hydrogen peroxide can be generated due to the action of ultrasonic waves and has sterilizing ability. Some people think that when the microbial cell fluid is subjected to high-frequency sound waves, the dissolved gas becomes small bubbles, and the impact of small bubbles can cause the cells to rupture. Therefore, ultrasonic waves have a certain killing effect on microorganisms.
High-energy ray sterilizing technology High-energy ray sterilizing is a kind of bactericidal method that utilizes the radiation emitted when the radioactive elements CO60 and Cs17 decay. The technique used for cold sterilization is ionizing radiation. The radiation produces direct and indirect effects during irradiation. The direct effect is the ionization and chemical action of the interstitial substance of the microbial cell irradiated by high-energy electrons; the indirect effect is the generation of water after receiving radiation. Ionization then interacts with other substances in the cell. These two effects block all intracellular activities and cause the death of microorganisms. For different strains, controlling different doses of radiation will not only destroy the color, smell and taste of foods; it will not have non-food substances, but the bactericidal effect is obvious. Therefore, the current sterilization technology is mostly used for meat products, fruit preservation and water treatment.
Low Temperature Conditioning and Sterilization France has developed this sterilization technology that is specially used for conditioning dishes. They mix the ingredients of the dishes in bags and perform low-temperature conditioning and sterilization under vacuum to avoid adverse effects on the quality of finished products caused by multiple heat sterilization. In recent years, Japan has developed low-temperature inflatable packaging sterilization technology, can also be applied to certain conditioning foods.
Biological preservation is considered natural preservation. The use of resistance to microorganisms or natural bacteriocins to control the growth of pathogenic bacteria inherent in foods and the growth of mycotoxin-producing fungi. This is one of the areas of active research and development in food biotechnology. It is very promising for development and application.
Active packaging refers to packaging technology that has special functions beyond the capabilities of conventional packaging. For example, adding oxygen-absorbing components to the packaging material eliminates the oxygen around the food during the preservation period of the packaged food and meets the requirements for food safety preservation. Compared with traditional packaging, active packaging is a new concept of packaging. It is to extend the shelf life of goods or improve the safety and organoleptic properties of food by changing the packaging conditions while maintaining the quality of the food. Active packaging is not only a barrier to products and the external environment, it combines advanced food packaging and materials science and technology to maximize the quality of packaged foods. The existing active packaging includes the following functions: deoxidation, deethyleneification, removal, release of CO2, humidity control, antibacterial, absorption of bad odor, release of ethanol, etc. Many active packaging has been widely used in the storage and transportation of food, medicine and daily necessities.
Microorganisms on the surfaces of antibacterial packaged foods are one of the main factors that affect the shelf life and safety of foods. Antibacterial can kill or immediately control the surface microorganisms in the processing, storage, transportation and processing of foods, prolong the shelf life and safety of foods. Combinations of packaging materials and preservatives, radiation treatment of the polymer of the packaging material, or air jets can all provide antimicrobial activity to the packaging bag.
Barrier (barrier) technology is an integrated approach that combines the various factors that constrain food preservation. It depends on the food subject, through the necessary processing, to establish a series of 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., to maintain the stability of the food in the shelf life. Some of China’s traditional meat products can be stored for a long time without refrigeration, and the principle is also here. Applying modern scientific methods, based on the identification of key factors related to the stability of food preservation, the development of this technology will help realize the industrialization of some traditional foods.
Membrane Separation Membrane Separation is a molecular-level separation. The main membrane system consists of dense and sparse membrane pores and can be divided into reverse osmosis (RO), nanofiltration (N), ultrafiltration (F), and microfiltration ( MF). Micro