Food sterilization technology

In recent years, energy-saving, safe, reliable, effective and low-cost packaging food sterilization technologies have been developed and applied one after another, which has greatly promoted the production and development of packaged foods.

Irradiation sterilization technology Irradiation sterilization technology is the use of radiation isotope cobalt 60, yttrium 157 generated γ-ray or low-energy accelerator radiation β-ray irradiation of packaged food. In Canada, Israel, France, Japan, and other countries, the radioactive substance cobalt 60 is commonly used. The strong gamma rays emitted by it can completely destroy the genetic factors of bacteria and completely destroy their physiological activity. When high doses are used, almost any bacteria can be eliminated.

Irradiation is completely sterilized: Irradiation of 2500 to 5000 kilorads of sealed foods can cause all pathogenic microorganisms that are damaged foods to die off, thus achieving the purpose of commodity disinfection. Before the irradiation, salt and sodium triphosphate can be added to the food, which can reduce the moisture loss of the food and enhance the ray's ability to kill bacteria.

The beef, chicken, ham, pork, sausage, fish, shrimp, etc. that have been treated by the irradiation complete sterilization method can be stored at room temperature (21° C. to 38° C.) for more than 2 years, and can maintain good color and fragrance.

Irradiation Sterilization and sterilization: doses of 100 to 1000 kilorads can effectively limit the growth of organisms and debilitating microorganisms that are detrimental to the health of the general population, and can effectively eliminate high-protein foods such as meat, dairy products, and egg products. Salmonella, irradiated with 500,000 rads, can be reduced by hundreds of millions of times, and it can also kill Salmonella deep inside frozen foods. More than 20 countries around the world have approved the use of radiation-sterilized foods for human consumption, such as chicken, pork, fresh fish, mushrooms, spices, potatoes, rice, and onions. Irradiated food is safe and reliable. After more than 40 years of practice in the world, it has been proved that irradiated food has never been found to have radioactive material residues and can maintain its original quality, color and flavor. In the United States, irradiated food has been brought into space, and astronauts have proved to be harmless to the body after eating. Irradiated foods have the advantage of long shelf life and can be kept fresh for a few years to kill bacteria, retard and delay the metabolism of the food itself, and eliminate the root causes of food deterioration. Irradiation sterilization can save a lot of energy. Any food sterilized by irradiation can only be stored in ordinary packaging, which saves a lot of materials such as can making, freezing and refrigerating, and energy. Irradiation preservation can replace some refrigerators.

Ultraviolet rays are irradiated by ultraviolet radiation, which means that the DNA of the target microorganism is killed by ultraviolet rays to chemically change the pyrimidine dimers to destroy the genetic factors and lose reproductive ability or death. The sterilization effect is the strongest at 250-260 nm. The powerful UV lamp developed abroad has an irradiation intensity of 200mw/cm2. It is a high-performance UV device and is safe and effective for sterilization of packaging materials.

Solid Surface Sterilizer: The packaged food is conveyed into the irradiation track through a conveyor belt, sterilized with a germicidal lamp, and then sent out with a conveyor belt. Foods suitable for plastic film packaging require packaging materials with a light-penetrating polyethylene or polypropylene plastic film.

Ultraviolet sterilizing liquid sterilizer: It can be divided into two types, external irradiating with external irradiation and internal irradiating with water and liquid flowing from the inside. The bactericidal effect can reach zero from the initial concentration after irradiation.

Ultraviolet sterilization requires little or no addition of bactericides and preservatives. It is more energy efficient, less costly, easier to maintain, safer to use, and does not damage food flavors and luster after sterilization. It is widely used. The United States has successively developed a series of products, and ultraviolet rays with a radiation amount several times larger than in the past have been put into practical use and can be gradually used for transmission. Ultraviolet sterilization, such as with heating, hydrogen peroxide, hot citric acid solution, ethanol, ultrasound and other treatment methods, the effect is better.

Microwave Sterilization Microwave disinfection is the use of microwaves to make water molecules vibrate and use molecular friction heat to sterilize. It is suitable for foods with poor thermal conductivity and foods that are easily degraded due to heating. For foods made of plastic packaging materials, they can be heat-sterilized from the food center in a short time under the condition of original packaging, and can also prevent secondary pollution. Microwave sterilization is only applicable to heat-labile microorganisms such as molds, yeasts, and E. coli. However, for foods with low moisture content attached to the back of foods, and microorganisms without moisture or induced small plastics or glass, the temperature cannot be fully increased. The effect is not significant.

The microwave heating method has two kinds of ovens or conduits. The latter is applied to the treatment of liquids, and the liquid is heated by flowing through glass tubes that are oblique to the tubes.

Aseptic packaging technology Aseptic packaging technology is a packaging technology in which sterilized and cooled aseptic foods are filled in presterilized containers under aseptic conditions and can be stored for a long time after being sealed. In the past decade, aseptic canning has evolved from fluids to solids, and packaging materials have moved from metal cans to packaging materials. Aseptic packaging technology has developed rapidly in Europe, the United States, Japan, and other countries, and is widely used in milk-based dairy products, fruit juices, and puddings. Processing foods such as meat and vegetables, vegetable juices, broths, refreshing beverages, coffee beverages, and soy milk.

Aseptic packaging has many advantages. The flavor and texture of the products are changed, as well as the loss of nutrient components and protein thermal denaturation. Aseptic packaging of meat products has no fat separation and gravy separation, and can maintain the original taste and flavor; the aseptically packaged juice is easy to store and taste Fresh and practical. Sterile packaging has low requirements on the strength of packaging containers. The material can be cardboard, plastic, aluminum and so on. In particular, the paper containers are low in cost, light in weight, free of metal dissolution, disposable, and simple to handle. 70% of the U.S. drinking milk is packed in paper. Aseptic packaging also has the advantages of saving energy and being suitable for mass production.

Aseptic packaging systems include the sterilization of foods and the filling and sealing of aseptic packaging. Food sterilization usually uses high-temperature short-time sterilization (HTST method) and ultra-high temperature instant sterilization (UHT), composite film made of heat-resistant plastic film and aluminum foil, can greatly shorten the sterilization time. Sterile filling and packaging of flexible packaging materials sterilization and hydrogen peroxide solution impregnation, spraying, hot air drying, or sterilization with gas germicide. The typical aseptic packaging device in the world includes the aseptic canning of Dole Inc. in the United States, which is used for fluids, colloids, and foods containing solids in metal cans, such as various puddings, condensed milk, paste-like foods, yoghurt fresh milk, and the like. The aseptic filling equipment consists of four parts: empty can, sterilizing, filling, sterilizing and sealing the can. When the empty cans are sterilized at 210°C-220°C for 45 seconds and enter the sterile room, the sterile water is sprayed from the lower part to cool the empty cans. Generally, the tanker can be used for continuous canning. Japan's MM aseptic filling device is to sterilize the styrene plastic film with hydrogen peroxide, heat the formed film and press it into a ring-shaped container, automatically quantitatively fill it, send the aluminum foil used for hydrogen peroxide sterilization, and seal it with a sealing film to cut off the film. For pudding, jam, ice cream, milk, juice and other aseptic filling.

In the process of aseptic packaging, in addition to the sterilization and sterilization of packaging materials and packaged foods, the whole operations of the workshop, working machinery, and air must be cleaned and sterilized, and the microbiologically controlled production management and circulation management must be thoroughly implemented.

At present, more applicable new sterilization technologies have also been developed. For example, the flame sterilizing method that enables direct heating of cans with gas flame during high speed rotation can accelerate heat conduction and prevent non-uniform heating. It is effective for canned foods and retort pouches; there is no need for sterilization of packaging materials, and food processing equipment is simple. The unique method of sterilizing liquid foods; the use of superheated steam to sterilize dried foods by air-disinfecting method will not make the raw materials damp like saturated steam, and it has good effect on grains and powdery foods.