Technical Information

Classification of heat sterilization

Writer: admin Time:2022-05-23 11:04 Browse:

Classification of heat sterilization
Thermal sterilization is to put the sealed food in a container into sterilization equipment, heat it to a certain temperature and keep it for a period of time. Its purpose is to kill the contaminated pathogenic bacteria, toxin-producing bacteria and spoilage bacteria in the food, and destroy the food in the food. Enzymes, as far as possible, maintain the original flavor, color, structure and nutritional components of the food content, and meet the requirements of commercial sterility.
Food is still mainly sterilized by heat at present, and its sterilization methods can be roughly summarized as follows:
①According to the sterilization temperature: pasteurization, low temperature sterilization, high temperature sterilization, high temperature short time sterilization;
②According to the sterilization pressure: it can be divided into normal pressure sterilization ( such as water as the heating medium, sterilization temperature ≤ 100 ℃ ) , pressure sterilization ( using steam or water as the heating medium, the commonly used sterilization temperature is> 100 ~135 ℃) ) ;
③According to the way of filling food containers in the sterilization process: can be divided into gap type and continuous type;
④Divided by heating medium: can be divided into steam sterilization, water sterilization ( full water type, water spray type, etc. ) , steam / gas / water mixed sterilization;
⑤According to the movement of the container during the sterilization process: it can be divided into static and rotary sterilization.
1 , pasteurization
Pasteurization was invented by the French Pasteur in 1865 and improved by later generations to kill pathogens and harmful microorganisms in liquids such as beer, wine, milk, and dairy products. It is also a method commonly used in the world. A method of sterilizing milk. At present, there are mainly two pasteurization methods commonly used in the world:
One is to heat the milk to 62 to 65 °C and keep it for 30 minutes. Using this method, various growth-type pathogenic bacteria in milk can be killed, and the sterilization efficiency can reach 97.3% to 99.9% . After disinfection, only some thermophilic bacteria, heat-resistant bacteria, and spores remain. Most of the bacteria are lactic acid bacteria, which are not only harmless to humans but also good for health.
The second method of heating the milk to 75 ~ 90 °C, incubated 15 ~ 6 seconds, the sterilization time which is shorter, more productive. But the basic principle of sterilization is to kill the pathogenic bacteria.
If the temperature is too high, there will be more nutrient loss. The most widely used temperature for pasteurization is 63-85 ℃. Nowadays, there is also sterilization at temperatures below 100 ℃, which is also called pasteurization in a broad sense.
2. Low temperature sterilization
Low temperature sterilization is a milder form of heat sterilization. The sterilization temperature is usually below 100 ℃, and it can have different temperature and time combinations. Low-temperature sterilization can inactivate enzymes in food and destroy heat-sensitive microorganisms and pathogenic bacteria in food. The storage period of sterilized products mainly depends on the sterilization conditions, food ingredients (such as pH ) and packaging. This method is mainly suitable for pH <4.6 acidic or acidified foods, low-temperature storage meat products, and yeast and mold as sterilization targets Food.
3. High temperature sterilization
High temperature sterilization refers to the sterilization treatment of food at a temperature above 100 ℃ under extraordinary pressure (pressure) . Mainly used in the sterilization of low-acid foods with pH > 4.6 .
4. Normal pressure sterilization and high pressure sterilization
Usually sterilization at a temperature below 100 ℃, generally in an open device, the sterilization with a pressure of one atmosphere is called atmospheric sterilization, while the temperature above 100 ℃ needs to be carried out in a closed device with a pressure greater than one atmosphere, which is customarily called High pressure sterilization. Generally, acidic foods and acidified foods can be sterilized under normal pressure at a temperature of 100 ℃ or below; for low-acid foods , high-pressure sterilization will be performed at a temperature above 100 ℃. In food factories, 121 ℃ is commonly used , and even higher temperatures are useful. Such as 127 ℃ temperature for thermal sterilization.
5 , static and dynamic disinfection sterilization 
( 1 ) The canned food is statically heat sterilized without rotating, which is called static sterilization.
( 2 ) The cans are rotated radially or axially during sterilization, and the contents move accordingly, which is called dynamic sterilization. This kind of sterilization heat transfer effect is better, the sterilization temperature is easy to be uniform, and the center temperature is easier to meet the requirements. For example, the canned eight-treasure porridge uses rotary sterilization to solve the problem of non-layering, which also plays a great role in improving the quality.
6 , intermittent and continuous sterilization sterilization
( 1 ) The traditional vertical and horizontal sterilization pots are both intermittent sterilization methods, that is, after one pot sterilization and cooling is completed, another pot sterilization is started.
( 2 ) Continuous sterilization machine
① with 100 ℃ or 100 below atmospheric temperature ℃ continuous sterilizer ( as commonly used in sterilization of canned fruit ) ;
②Use a high-pressure continuous sterilization machine with a temperature above 100 ℃, such as a hydrostatic continuous sterilization machine used in large factories, and a water-sealed horizontal continuous sterilization machine manufactured by ACB in France .
7 , high temperature short time sterilization
At present, there is no clear definition of high temperature and short-term sterilization in the world, but it is generally considered that the pH is greater than 4 in aseptic packaging . 6 low-acid food, the sterilization temperature is 135 ~ 145 ℃, the time is 1 ~ 30 seconds, it is called high temperature and short time sterilization, which is also the common process procedure for sterilization of most aseptic packaged low-acid foods. Sterilization temperature is 150 ~ 166 ℃, time is 0 .1 to 0.01 seconds is called ultra-high temperature instant sterilization.
8 , aseptic filling food sterilization
Aseptic filled food refers to the product that is sterilized before being filled and sealed. The sterilization procedure must specify the specific sterilization time or the time to stay at a certain temperature. During the filling operation, the entire filling system must maintain the sterile state, and ensure that the packaging materials are sterilized with high temperature (such as steam) or chemical disinfectants (such as hydrogen peroxide) before filling the food, and no heat sterilization is required after the product is sealed.
9. Heat transfer medium for sterilization
( 1 )Sterilization temperature at 100℃ or below, usually with water as the heat transfer medium.
( 2 ) When the sterilization temperature is above 100 ℃, steam is usually used as the heat transfer medium.
( 3 ) Superheated water above 100 is used as heat transfer medium.
( 4 ) Use a mixture of steam and water as the heat transfer medium.
( 5 ) Use a mixture of steam, water and air as the heat transfer medium.







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