New technologies for packaging food sterilization have been developed and applied
In recent years, the sterilization technology of packaged foods that save energy, safety, reliability, good effect and low cost has been developed and applied one by one, which greatly promotes the production and development of packaged foods.
Irradiation sterilization technology
The irradiation sterilization technique irradiates the packaged food with the radiation isotope cobalt 60, the T-ray generated by the 铯l57 or the D-ray emitted by the low-energy accelerator. Canada, Israel, France, Japan and other countries generally use the radioactive cobalt 60, which emits strong r-rays that can completely destroy the genetic factors of bacteria, completely destroying their physiological activities, and can almost eliminate any bacteria when used at high doses.
Irradiation completely sterilized: irradiating the sealed packaged food with 2500 5,000 rads, which can kill all the pathogenic microorganisms that damage the food, thus achieving the purpose of commodity sterilization. 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 killing ability of the radiation on the bacteria. Beef, chicken, ham, pork, sausage, fish and shrimp, which have been treated by irradiation and complete sterilization, can be stored at room temperature (2l °C ~ 38 °C) for more than 2 years, which can maintain good color and aroma.
Irradiation sterilization: The dosage of 100-1000 kilorads can effectively limit the growth of harmful organisms and destructive microorganisms, which can harm the health of high-protein foods (such as meat, dairy products and egg products). Large Salmonella, which is irradiated with 500,000 rads, can reduce it by 100 million times and kill Salmonella deep in frozen food. Irradiated foods are safe and reliable, and irradiated foods have never been found to have residual radioactive materials, which can maintain the original quality and color and aroma. The advantage of irradiated food is that it has a long storage period and can be kept fresh for several years, which not only kills bacteria, but also inhibits and delays the metabolism of the food itself, and eliminates the root cause of food deterioration. After irradiation sterilization, it can save a lot of energy. Any food can be stored in the ordinary package after being sterilized by irradiation. It can save a lot of cans, frozen and refrigerated materials and energy. Radiation preservation can replace some refrigerators.
Ultraviolet radiation: Ultraviolet radiation is the use of ultraviolet light to kill the DNA of the target microorganism, causing it to undergo chemical changes, forming a pyrimidine dimer, destroying the genetic factors and losing the ability to reproduce or die. The bactericidal effect is 250-260 rim. The powerful UV lamp developed abroad has an irradiation intensity of 200mW/cm, which is a high-performance ultraviolet device, which is safe and effective for the sterilization of packaging materials.
Solid surface sterilizer: The packaged food is passed through a conveyor belt, sent to a human orbit, sterilized by a germicidal lamp, and then sent out by a conveyor belt. Foods suitable for plastic film packaging require polyethylene or polypropylene plastic film with good light transmittance.
Ultraviolet sterilizing liquid sterilizer: It can be divided into two types, an external illuminating type with external illumination and an internal illuminating type for allowing water and liquid to flow from inside. After irradiation, the bactericidal effect can reach zero bacterial concentration from the initial bacterial concentration.
The United States has developed a series of products, and the ultraviolet rays, which are dozens of times larger than the past, have been put into practical use and can be gradually used for transmission. Ultraviolet sterilization, such as heating, hydrogen peroxide, hot citric acid solution, ethanol, ultrasonic and other treatment methods, the effect is better.
Microwave sterilization
Microwave sterilization is the use of microwaves to vibrate water molecules, using the frictional heat generated by molecules to sterilize, suitable for foods with poor thermal conductivity and foods that are easily degraded by heating. It can also be used in foods such as plastics and other packaging materials such as vegetable juices, broths, refreshing drinks and coffee drinks. It can be heat-sterilized from the food center in a short period of time under the original packaging, and can prevent secondary pollution. Microwave sterilization is only applicable to heat-labile microorganisms such as mold, yeast, and Escherichia coli. However, microorganisms that adhere to the back of food, have low moisture content, and microorganisms that do not contain water and induce small plastics or glass cannot be sufficiently heated. The effect is not significant. Microwave heating has two types of ovens or conduits, the latter being used to treat liquids that are heated through a glass tube that is slanted through the conduit.
Aseptic packaging technology
Aseptic packaging technology is a packaging technology that can be stored in a pre-sterilized container under sterile conditions after being sterilized and cooled, and sealed for long-term storage. In the past 10 years, aseptic cans have been developed from fluids to solids, and packaging materials have been moved from metal cans to packaging materials. Aseptic packaging technology has developed rapidly in Europe, America, Japan and other countries. It is widely used in dairy-based dairy products, juices, Pudding, meat, yogurt, fresh milk, etc. The aseptic filling equipment consists of four parts: empty can sterilization, filling, can lid sterilization, and sealing. When the empty tank is sterilized at 2100 °C ~ 220 °C for 45 S and then enters the sterile room, the sterile water is sprayed from the lower part to cool the empty tank. Generally, the tank can be continuously filled by a tank flow type can. In Japan, the MM aseptic filling device sterilizes the styrene plastic film with hydrogen peroxide, and then heats the formed film into a ring-shaped container, automatically fills it, and sends out the aluminum foil for the cover sterilized by hydrogen peroxide. The film is sealed with a sealing film, and the film is cut. For aseptic filling of pudding, jam, ice cream, milk, juice, etc.
In the aseptic packaging process, in addition to disinfecting and sterilizing packaging materials and packaged foods, the entire operation of the workshop, working machinery and air should be clean and sterilized, and the production management and circulation management of microbial control should be thoroughly realized. Aseptic packaging systems include both sterilization and aseptic filling of foods. Food sterilization is usually carried out by high-temperature short-time sterilization (HTST method) and ultra-high temperature instant sterilization (UHT). 70% of the US drinking milk is packaged in paper, which can be discarded after use and is easy to handle. Typical aseptic packaging devices in the world include aseptic cans from Dole, USA, fluids for metal cans, colloids, and foods containing solids, such as various puddings, condensed milk, and sauces.
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