Sterilization techniques for food aseptic packaging
Sterilization is one of the key technologies in food aseptic packaging, expecially for the retort packaging. The scope of sterilization includes food, packaging materials (containers), working environment, equipment, and the like. Sterilization methods can be roughly divided into physical methods and chemical methods. Physical methods mainly include steam (high temperature), electromagnetic waves and irradiation. Steam sterilization is a classical sterilization method, and electromagnetic wave sterilization uses 2450 nm and 915 nm microwave sterilization and ultrasonic sterilization. Irradiation sterilization can be divided into ionic irradiation and non-ionic irradiation. Non-ionic irradiation uses the most widely used ultraviolet light with a wavelength of 253.7 nm. Due to the limitation of the intensity of the light source, there is no residual problem, but the above physical sterilization methods have certain limitations. Chemical methods mostly use strong oxidants, such as hydrogen peroxide, peracetic acid, ethylene oxide, halogen, etc. Chemical sterilization mainly relies on the oxidation ability of strong oxidants and the combination of -SH-thiol in cellular enzyme protein to convert to -SS - base, destroying the molecular structure of the protein, interfering with the metabolism of the bacterial enzyme system, rendering it inactive. According to molecular biology, it is the oxidative damage of the DNA of cells, thereby inhibiting the proliferation of cells. The use of chemical sterilization produces a certain amount of residual contamination of containers and packaging materials as well as equipment. Strict measures must be taken to control the residues to ensure the safety of the final product. In summary, the sterilization techniques in food aseptic packagings are mainly as follows.
1. Thermal sterilization technology
The use of heat to kill harmful microorganisms in food is both an ancient method and a sterilization technique that is extremely important in modern times. In 1804, the French appert (Appert) invented a method of bottling food in boiling water for a period of time, which can preserve food for a long time. In the 1950s, the French Pasteur described the mechanism of microbial spoilage in food and laid the theoretical foundation for the development of sterilization technology. Food heat sterilization can be divided into low temperature sterilization method, high temperature short time sterilization method and ultra high temperature instant sterilization method.
(1) Low temperature sterilization, also known as pasteurization, sterilization conditions are 61 degrees Celsius to 63 degrees Celsius / 30 minutes, or 72 degrees Celsius to 75 degrees Celsius / 15 minutes to 20 minutes. Pasteurization technology is to fill the food container and seal it in a packaging container, and keep the temperature below 100 degrees Celsius for a certain period of time to kill the bacteria in the packaging container. Pasteurization can kill most pathogenic bacteria, but the killing ability of non-pathogenic spoilage bacteria and their spores is insufficient. If pasteurization is combined with other storage methods, such as refrigeration, freezing, deoxidation, Packing and matching can meet the requirements of a certain shelf life. Pasteurization technology mainly uses the citrus and apple juice beverages to sterilize foods. Because the pH value of juice foods is below 4.5, there is no microbial growth, and the sterilization targets are yeast, mold and lactobacilli. In addition, pasteurization is also used for the sterilization of jams, canned syrup, beer, canned vegetables, pickles, and the like. Pasteurization has reliable acid resistance for sealed acidic foods. For those low-acid foods that are not resistant to high-humidity treatment, as long as the consumption habits are not affected, the pH is often obtained by means of acid addition or by means of microbial fermentation. In the range of acidic foods, low temperature sterilization can be used to preserve food quality and storage. This method takes a long time and should not be used for heat-sensitive foods.
(2) High temperature short-time sterilization (HTST): sterilization conditions are 85 degrees Celsius to 90 degrees Celsius / 3 minutes to 5 minutes, or 95 degrees Celsius / 12 minutes, mainly used for low temperature circulation of sterile milk and low acid juice drinks For sterilization, the heat exchanger can be used to heat the liquid material to nearly 100 degrees Celsius in an instant, and then to cool to room temperature. This method takes a short time and has a good effect, which is beneficial to product quality. Mainly can kill yeast, mold, lactic acid bacteria and so on. These two methods have the characteristics of stable sterilization effect, simple operation, small equipment investment and long application history. Nowadays, they are widely used in the sterilization of all kinds of canned food, beverage, alcohol, medicine and dairy packaging.
(3) Ultra-high temperature instantaneous sterilization (UHT): It was introduced in 1949 with the appearance of the Stork device, and various types of ultra-high temperature sterilization devices have appeared internationally. Ultra-high temperature short-time sterilization is to heat the food to a high temperature (above 130 degrees Celsius) for sterilization purposes. It can be divided into direct heating and indirect heating. The direct heating method uses high pressure steam to directly spray the food, so that the food can be heated at the fastest speed, reach 140 degrees Celsius to 160 degrees Celsius in a few seconds, maintain for a few seconds, then remove the moisture in the vacuum chamber, and then cool it with a sterile cooler. Room temperature. The indirect heating method is based on the viscosity and particle size of the food, and the plate heat exchanger, the tube heat exchanger, and the scraper heat exchanger are selected. The plate heat exchanger is suitable for liquid foods with a pulp content of no more than 1% to 3%. The tubular heat exchanger has a wide adaptability to the product, and can process liquid foods such as concentrated fruit and vegetable juice with high pulp content. A tubular heat exchanger can be used for products that use a plate heat exchanger to cause coking or clogging, and which have insufficient viscosity to use a squeegee heat exchanger. The scraper heat exchanger is equipped with a rotator with blades, which is scraped on the heating surface to push the high-viscosity food forward to achieve the purpose of heat sterilization. The effect of ultra-high temperature instantaneous sterilization is very good, almost reaching or close to the requirement of complete sterilization, and the sterilization time is short, the nutrient destruction in the material is less, the food quality is almost unchanged, and the preservation rate of nutrients is over 92%, production The efficiency is very high, and the effect is better than the other two kinds of heat sterilization methods. The ultra-high temperature sterilization device with the aseptic packaging technology of food has developed rapidly at home and abroad, and has now developed into a high-tech food sterilization technology. At present, this sterilization technology has been widely used for the sterilization of milk, soymilk, wine, juice and various beverages, and the food can be sterilized by immersing it in hot water at this temperature.
2. Superheated steam sterilization technology
Also known as dry heat sterilization. It is sterilized by high-temperature superheated steam, which is sprayed on the items to be sterilized by superheated steam with a temperature of 130 ° C to 160 ° C. The sterilization operation can be completed in a few seconds. At present, the superheated steam sterilization technology is only suitable for heat resistance. Sterilization of food packaging containers (such as metal products, glass products, etc.). Metal cans are one of the earliest packaging materials for aseptic packaging. They are mainly divided into tinplate cans and aluminum cans. The most advanced representative of the world's metal cans aseptic packaging is the American Dole Aseptic Canning System. This sterilization technique is employed. The method is that when the empty tank passes through the sterilization chamber on the conveyor chain, the superheated steam is sprayed from the upper and lower sides for 45 seconds, at which time the tank temperature rises to 221 degrees Celsius to 224 degrees Celsius, and the can lid is also sterilized by superheated steam of 287 degrees Celsius to 316 degrees Celsius for 75 seconds. At 90 seconds, this high temperature is enough to kill all the heat-resistant bacteria. Since all containers and equipment are sterilized by superheated steam, the degree of sterility is high, the residual air in the top gap of the can is extremely small, and the vacuum is high, and the quality of the product is safe and reliable.
3. Resistance heating sterilization technology
Also known as ohmic sterilization, it is a new type of heat sterilization technology that uses the current of a person to generate heat inside the food for sterilization purposes. It uses electrodes to direct current directly into the food, and the heat is generated by the dielectric properties of the food itself for sterilization purposes. Resistance heating and sterilization use AC frequency from 50Hz to 60Hz. The applicability of resistance heating is determined by the electrical conductivity of food materials. Most foods that can be pumped and dissolved with salt ions and have a water content of more than 300% are used. It can be sterilized by resistance heating, and the effect is very good, and some non-ionized foods such as fat, sugar, oil, and treated water without added salt are not suitable for this technology. As a high-tech application of ohmic sterilization, broth foods containing granules, such as beef diced and carrot diced, have a key role in improving product hygiene safety and quality flavor quality, facilitating process control and reducing operating costs.
Tests at the APV Food Processing Center in the UK have shown that resistance heating has been successfully used for the sterilization of a variety of foods and flakes containing large particles, such as potatoes, carrots, mushrooms, beef, chicken, flaky apples, pineapples, peaches, etc. For foods with particles (particle size less than 20mm), conventional heat exchangers are indirectly heated and sterilized. The heat is first transferred from the heating medium through the partition to the liquid in the food material, and then by the convection between the liquid and the solid particles. Conduction is transmitted to the solid particles, and finally to the heat transfer inside the solid particles. Obviously, in order to achieve the sterilization temperature inside the particle, the surrounding food medium must be overheated, which will inevitably lead to the soft and rotten texture and the deterioration of the shape of the granular food, which will affect the flavor and quality of the product. Using ohmic sterilization technology, the heating rate of the particles can be close to the heating rate of the liquid, and the heating rate can be obtained faster than the conventional heat sterilization method (the temperature of the particles is about 1 degree Celsius/second to 2 degrees Celsius/second) to obtain high quality. The product. Therefore, it is more suitable for continuous sterilization of acidic and low-acid foods and granular foods.
4. Irradiation sterilization technology
Since the peaceful use of atomic energy, after more than 40 years of research and development, people have successfully used atomic radiation technology for food sterilization and preservation. Irradiation is a cold sterilization method that uses krypton, beta, gamma rays or accelerated electron rays (most commonly gamma rays of Co60 and Cs137) to penetrate the food to kill microorganisms and insects in the food. Irradiated foods or organisms form ions, excited molecules or molecular fragments, which in turn interact to form compounds different from the original material. On the basis of chemical effects, irradiated materials or organisms A series of biological effects occur, which causes pests, eggs, proteins, nucleic acids and enzymes that promote biochemical reactions to be destroyed and lose vitality, thereby ending the process of agricultural products, food erosion and growth aging, and maintaining quality stability. Irradiated fresh food has antiseptic effect such as insecticide and sterilization. It does not generate heat or damage the shape of food. It can maintain the original color, aroma, taste and nutrients of food, and can be preserved at room temperature for a long time. It is a kind of fast-growing food high-tech. It is widely used in developed countries. There are more than 60 irradiation devices in China (more than 100,000 curies). The radiation used for irradiation packaging has the characteristics of strong penetrating power and high lethality. Through the irradiation of such rays, pathogenic bacteria, microorganisms and insects parasitic in food are killed. At the same time, the food can inhibit the metabolism of the food itself after irradiation treatment, thus preventing the deterioration and mildew of the food.
At present, the radiation of irradiation energy can be adjusted or controlled to a predetermined penetration depth, in which case it affects at most the surface state of the polymer packaging material or the selected food surface to be sterilized, without Affects the food characteristics and quality within aseptic packages that are subjected to irradiation sterilization. In addition to the nutritional and high taste of food, the safety of irradiated packaging has attracted people's attention. Since the food is not in direct contact with the source of radiation when it is subjected to irradiation sterilization, only the radiant energy of the received radiation acts on the food, and thus there is no problem of residual radioactivity in the product. However, it has been found that when the polymer material is irradiated by radiation, gas decomposition products are present, and these decomposition products may have an effect on the packaged article. The results show that these gas decomposition products have a great relationship with the plastic composition and the ambient oxygen pressure, but after adding plasticizers and stabilizers, this situation will be inhibited to varying degrees.
Under normal circumstances, when the irradiation line (including X-ray, β-ray and γ-ray) is irradiated, the dose is too high to accelerate the aging and decomposition of the packaging material. Therefore, it is necessary to pay attention to controlling the radiation dose, and the packaging material needs thick protection. Floor. In addition, irradiated glass bottles can cause discoloration of glass bottles, so this method is only used for heat sensitive plastic bottles, composite films and paper containers. According to the total amount of irradiated decomposition products, the decomposition amounts of different plastics are different, that is, they are different in stability due to irradiation, and materials such as PET and PS have the best stability. At the same time, within the reasonable range of food disinfection dose, the permeability of the packaging material and the material barrier properties did not change much. In short, irradiation aseptic packaging is a new technology, which has been widely used in developed countries in the world because of its good disinfection effect, fast speed, ability to maintain food characteristics, energy conservation and environmental protection. It is also a new packaging technology recognized by the World Trade Organization (WTO). At present, irradiated aseptically packaged foods have been included in the ranks of green foods.
5. Microwave sterilization technology
Microwave refers to an electromagnetic wave having a wavelength of 0.001 m to 1 m (frequency of 300 MHz to 300,000 MHz). It can advance forward at the speed of light, encounters object blocking, can cause reflection, penetration, absorption, etc. The microwave frequency used for sterilization is 2450MHz. The microwave can cause the water molecules in the material to vibrate, rub and heat, and the microorganisms are killed by heat to sterilize. The results of the study generally suggest that microwaves have two factors in the lethal effect of microorganisms, namely thermal and non-thermal effects. The thermal effect means that the material absorbs microwave energy and raises the temperature to achieve the sterilization effect. The non-thermal effect refers to the strong rotation effect of polar molecules in the living body in the microwave field. This strong rotation inactivates the vegetative cells of the microorganisms or destroys the enzyme system in the microbial cells, causing the death of the microorganisms. Microwave sterilization has strong penetrating power, energy saving, fast sterilization, high efficiency, simple operation, wide application range, microwave sterilization for easy control, uniform heating, food nutrients and color, aroma and taste after sterilization. Still close to the natural quality of food, it can be used for the sterilization of liquid and solid objects. The packaged items are placed in the microwave field and the sterilization process can be completed in a very short time. However, care should be taken to prevent microwave leakage during use. At present, microwave sterilization is mainly used for sterilization of meat, fish, soy products, milk, fruits and beer.
6. Far infrared sterilization technology
The thermal effect of far infrared rays can be sterilized, it can directly illuminate the food, or it can be sterilized by far infrared ray after the food is placed in a plastic bag. The use of infrared light began in the 20th century. In 1935, Groveny of Ford Motor Company of the United States first obtained the patent for heating and drying infrared rays. Many components and microorganisms in foods have strong absorption in the far infrared region of 3 μm to 10 μm. Far-infrared heat sterilization does not require media, and heat directly penetrates from the surface of the object to the inside, so it can be used not only for the sterilization of general powdery and blocky foods, but also for the elimination of nut foods such as coffee beans, peanuts and grains. Direct sterilization of fungi and mildew and bagged food. The infrared aseptic packaging machine pioneered by Japan Sanz Co., Ltd. consists of ML-501 type packaging machine and MS-801 channel type infrared heat shrinking machine. The machine can choose the heat shrinkable film of the corresponding thickness and color according to the shape and size of the packaged object, and sterilize in the heat radiation. The sterilization process is simple, the packaging quality greatly exceeds the manual packaging, and the packaging efficiency is improved by 6 times. ~ 8 times.
7. UV sterilization technology
Ultraviolet sterilization is a simple and convenient sterilization method, and has no drug residue, high efficiency, high speed, and can be reflected by different surfaces, with weak penetrating power, and the sterilization effect on liquid materials is ideal. When used, liquid materials such as beverages, milk, and the like can be sterilized by passing through the ultraviolet irradiation zone in a thin layer. UV sterilization can be applied to the sterilization of food surfaces, food packaging materials, food processing workshop environments, equipment, appliances, and work benches. However, ultraviolet rays must be irradiated to be sterilized, and if not irradiated, they cannot be sterilized. Moreover, the ultraviolet light is linearly propagated, and its intensity is weakened in proportion to the square of the distance. The sterilization effect is related to the irradiation intensity, time, distance, and air temperature. Therefore, it is necessary to determine the irradiation distance and time according to the power of the ultraviolet lamp. In addition, UV sterilization is also related to the surface condition of the material. For packaging materials with smooth surface and no dust, ultraviolet rays can kill bacteria on the surface; for embossed aluminum foil surface, the sterilization time is three times longer than smooth surface; on the surface of a regular-shaped packaging container, the sterilization exposure time is five times longer than the plane. At the same time, the characteristics of the material should be considered when using ultraviolet sterilization, especially the inner layer of the composite material, such as PVC, PVDC, LDPE and the like, which will reduce the heat seal strength by about 50% after being irradiated by ultraviolet rays. If UV is combined with air heating, hydrogen peroxide and ethanol sterilization methods, it can greatly enhance its sterilization ability.
8. Magnetic sterilization technology
Magnetic sterilization is to place the food that needs to be sterilized and sterilized in a magnetic field, and under the action of the set magnetic field strength, the food is sterilized at normal temperature. Since this sterilization method does not require heating, it has a broad-spectrum sterilization effect, and the flavor and quality of the processed food are not affected. This sterilization method is mainly applicable to various beverages, liquid foods, seasonings and other solid foods in various packages.
9. High voltage electric field pulse sterilization technology
High-voltage electric field pulse sterilization is to place food in an instantaneous high-voltage electric field generated between two electrodes. High-voltage electric pulse (HEEP) can destroy the cell membrane of bacteria and change its permeability, thereby killing cells. There are two methods for obtaining a high voltage pulsed electric field. One is to use the principle of LC oscillating circuit to charge a group of capacitors with a high-voltage power supply, and connect the capacitor to an inductor coil and the electrode of the processing chamber. The high-frequency exponential pulse attenuation wave generated when the capacitor is discharged is added to the two electrodes. A high voltage pulsed electric field is formed thereon. Since the LC circuit discharges the electrode quickly, the electric field energy can be released within tens to hundreds of microseconds, and the LC oscillator circuit can be continuously charged and discharged by using an automatic control device, which can be completed within several tens of milliseconds. Bacterial process. The other is to use a specific high-frequency high-voltage transformer to obtain a continuous high-voltage pulsed electric field. The high-voltage pulsed electric field intensity for sterilization is generally 15 kV/cm to 100 kV/cm, the pulse frequency is 1 kHz to 100 kHz, and the discharge frequency is 1 kHz to 20 kHz. High-voltage electric field pulse sterilization is generally carried out at room temperature, and the processing time is several tens of milliseconds. This method has two characteristics: First, due to the short sterilization time, the energy consumption during the treatment is much smaller than the heat treatment method. Second, because it is carried out under normal temperature and normal pressure, the processed food has little change in physical properties, chemical properties and nutrients compared with fresh food, and there is no difference in flavor and taste. Moreover, the sterilization effect is obvious, and the requirements for commercial sterility can be achieved, and the utility model is particularly suitable for heat-sensitive foods, and has broad application prospects.
10. Pulsed light sterilization
Pulsed light sterilization is sterilized by intense white light flashing, consisting of a power unit and an inert gas lamp unit. The power unit is a component that provides high voltage and high current pulses. It supplies energy to the inert gas lamp. The inert gas lamp emits light from the ultraviolet to the near infrared region. The spectrum is very similar to the sunlight, but the intensity is thousands of times stronger. Up to tens of thousands of times, the light pulse width is less than 800 μs. This technology can be used to extend the shelf life of foods and fresh foods packaged in transparent materials by treating only the surface of the food and thus having little effect on the flavor and nutrients of the food. Studies have shown that pulsed glare has a strong lethal effect on Bacillus subtilis and yeast, and after more than 30 flashes, these bacteria can be reduced from 105 to 0. The wavelength band from which the pulsed light is sterilized may be ultraviolet light, but other bands may have synergistic effects.
11. Excited state ultraviolet pulse sterilization
This is one of the most promising sterilization technologies recently developed. The excited state ultraviolet pulse sterilization technology is different from the conventional physical sterilization method. It uses a special light source and power supply device to generate a single wavelength of 253.7nm ultraviolet light under high frequency and high pressure, and its intensity can reach 200mw/cm3 or more. Ultraviolet devices emit 200 to 300 times the intensity of the luminescence, and the pulse can reach nanoseconds. The energy is enough to break the C-H bond, C-N bond and O-H bond in the DNA structure of the cell, causing the DNA structure to be lethal. Damage, if synergistic with low concentrations of hydrogen peroxide, can not only increase the sterilization intensity, but also decompose residual hydrogen peroxide. The application of this new technology will provide a powerful microbial barrier system for aseptic packaging equipment. Technical Support.
12. Ultra-high pressure sterilization technology
In recent years, Japan has developed a new type of food processing and preservation technology, which is the ultra-high pressure sterilization technology. Ultra-high pressure treatment has some advantages not in heat treatment and other processing methods. It can maintain the original flavor composition, nutritional value and color of foods (such as meat), and kill the common yeast, E. coli and grapes in food. Cocci and the like for sterilization purposes. The so-called high static pressure technology (HHP) is to seal food in an elastic container or placed in a sterile pressure system (usually using water or other fluid medium as a medium for transmitting pressure), and is treated under high static pressure (generally 100 MPa or more). For a period of time, to achieve the purpose of processing and preservation. Under high pressure, proteins and enzymes are denatured, and microbial cell nuclear membranes are pressed into small pieces and protoplasms together to become a paste. This irreversible change can cause microbial death. Microbial death follows the first order reaction kinetics. For most non-spore microorganisms, the sterilization effect is good at room temperature and pressure of 450 MPa. Spore spores are pressure-resistant, require higher pressures for sterilization, and are often more effective in combination with other treatments such as heating. Temperature, medium, etc. have a great influence on the mode and effect of food ultra-high pressure sterilization. Intermittent repeated high pressure treatment is a good method to kill pressure-resistant spores. The ultra-automated sterilizer newly developed in Japan has an operating pressure of 304 MPa to 507 MPa. The biggest advantage of ultra-high pressure sterilization is that it has no effect on flavor substances, vitamin C, color in food, and has little loss of nutrients. It is especially suitable for sterilization of foods such as juice, jam and meat. In addition, when the meat is sterilized by ultrahigh pressure of 300 MPa to 400 MPa, the muscle fibers can be broken and the tenderness of the meat food can be improved.
13. High hydrostatic sterilization technology
The high hydrostatic pressure technology utilizes the liquid as a pressure transmitting medium to make the food in a high pressure state and achieve the purpose of sterilization. The operating temperature is low, the thermal damage to the food is small, and the treated product is suitable for aseptic filling. A professor at the University of Georgia in the United States used continuous high hydrostatic pressure equipment to sterilize orange juice, and then filled it with laboratory aseptic packaging equipment. The product was stored at 40 ° C for 90 days without any deterioration and maintained the original color and flavor. The aseptic packaging equipment is composed of a box body, a nitrogen gas conveying pipe, a high temperature and high pressure steam conveying pipe and a material conveying pipe. For filling, the packaging container is placed in the box, sterilized by high temperature steam, and then the autoclaved material is passed, and finally sealed with nitrogen.
14. Ultrasonic sterilization technology
Ultrasound is a sound wave with a frequency greater than 10 kHz. Ultrasonic waves are the same as ordinary sound waves. The interaction between the ultrasonic wave and the sound-transmitting medium contains enormous energy. When it encounters the material, it produces rapid alternating compression and expansion. This energy is enough to kill and destroy microorganisms in a very short time. Moreover, it can also produce various effects such as homogenization, aging, and cleavage of macromolecular substances, and has multiple effects that are difficult to obtain by other physical sterilization methods, thereby improving food quality and ensuring food safety. The technician used the ultrasonic generator as a sterilization device, and the soy sauce was used as a sterilization target, and good results were obtained.
15. Membrane filtration sterilization technology
With the development of materials science, various membranes that can be used for material separation have appeared one after another. Membrane separation technology has been widely used in industrial production such as food, biopharmaceutical, etc., such as extraction of biochemical substances, preparation of pure water, concentration of fruit juice, etc. The membrane separation process can be roughly divided into two types depending on the driving force. One is a membrane process that uses pressure as a driving force, such as ultrafiltration, and the other is a membrane process that is driven by electricity, called ion exchange, such as electrodialysis. The pressure-driven membrane process can be divided into microporous filtration, ultrafiltration and reverse osmosis according to the pore size and retention capacity of the membrane. Typically, the pore size of the membrane is from 0.0001 microns to 10 microns, and the size of the microbial particles in the material is typically from 0.5 microns to 2 microns. If a membrane having a pore size smaller than that of a microorganism is used, and the liquid is filtered through a membrane filter, the bacterial particles are trapped, which is called filtration sterilization. Membrane filtration sterilization technology has the advantages of low energy consumption, operation at normal temperature, suitable for heat sensitive materials, strong process adaptability, etc. It has broad application prospects and is widely used in food, biochemistry, pharmaceutical, water and air, dairy products, juices. Filtration and other sterilization.
16. Ozone sterilization technology
The mechanism of ozone sterilization is that O3/H2O forms a strong oxidizing electrode potential, so it has a destructive effect on the cell membrane and phospholipids and proteins in the cell wall. When O3 enters the cell, it destroys the enzyme and genetic material, thereby killing the microorganism. The ozone is mixed with water to form ozone water, which can replace the hydrogen peroxide treatment aseptic packaging container. At the same time, due to its half-life (5 minutes to 14 minutes), ozone is extremely unstable in water, and a reduction reaction occurs at all times, producing monoatomic oxygen with strong oxidation. At the moment of its production, it chemically reacts with lipoproteins or proteins in the bacterial cell wall, thereby destroying the cell wall and cell membrane of the bacteria, increasing the permeability of the cell membrane, and allowing the bacteria to inactivate the bacteria. . At the same time, ozone can rapidly diffuse into the cells, oxidizing the enzymes or HNA and DNA in the cells, thereby killing the bacteria. Ozone sterilization is highly efficient, fast, safe, and inexpensive. Since its discovery in 1785, it has been widely used in food processing, transportation and storage, and in the production of tap water and purified water. Ozone water sterilization speed is 300 to 1000 times faster than chlorine water. At the same time, ozone is also very effective for environmental sterilization, and it can also remove odor.
17. Hydrogen peroxide (hydrogen peroxide) sterilization technology
Hydrogen peroxide is a sterilizing agent with strong sterilization ability and has a broad-spectrum sterilization effect on microorganisms. The sterilization power is related to the concentration and temperature of hydrogen peroxide. The higher the concentration and the higher the temperature, the better the sterilization efficiency. At normal temperature, the sterilization effect of hydrogen peroxide is weak. Hydrogen peroxide is usually used for sterilization of packaging containers and auxiliary devices. When sterilized with hydrogen peroxide, the concentration is generally controlled at 25% to 30%, and the temperature is 60 to 65 °C. The method of application includes a dipping method (that is, immersing the packaging material or the container in hydrogen peroxide water), a spraying method (that is, spraying a hydrogen peroxide spray onto the packaged article), so that a uniform hydrogen peroxide solution is formed on the surface of the packaging material, and then the heat is radiated. Completely decomposes into harmless water vapor and oxygen while enhancing the sterilization effect. However, in the sterilization, hydrogen peroxide is rarely used alone, and it is often used in combination with other sterilization techniques. For example, hydrogen peroxide + heat, which is a widely used method, almost all packaging materials can be treated in this way. Soak or spray with hot hydrogen peroxide, then heat to volatilize and decompose the hydrogen peroxide remaining on the surface of the packaging material. The heating itself also has a bacteriostatic effect. Different devices have different heating methods, but generally they are mostly heated by sterile hot air. Typical systems include Tetra Pak Aseptic Stuffing System from Sweden Tetra Pak, Aseptic Filling System in International Paper, Combiloe Aseptic Filling System from PKL, Germany, Hydrogen Peroxide + Ultraviolet, ie Low Concentration Hydrogen Peroxide (<1%) The solution, together with high-intensity ultraviolet radiation sterilization, achieves a good sterilization effect, which is more effective than the sterilization treatment with hydrogen peroxide. This sterilization method requires immediate sterilization at room temperature. The requirement to sterilize with a reagent such as hydrogen peroxide is to ensure that the drug residue of the article should be lower than the specified requirements.
In addition, there are other sterilization technologies in food aseptic packaging, such as chlorine dioxide sterilization technology, ethylene oxide sterilization technology, chlorine sterilization technology, and electronic sterilization technology. Different sterilization techniques can be used in combination to make the sterilization effect more ideal, such as heating and pressing, sterilization technology, heating and chemical sterilization, heating and irradiation, sterilization, electrostatic sterilization, etc. - These technologies are constantly being researched and fully refined. It is believed that these technologies will gradually be widely used in food and other aseptic packaging fields in the near future.