Sterilization is a relatively mild form of heat treatment, the effect on milk is not significant, there is no obvious taste of steaming, the degree of denaturation of whey protein is low, there is only a very small amount of heat-sensitive nutrient loss, which can basically maintain the nutritional value of cow’s milk. After sterilization of cow’s milk, the pathogenic bacteria and germs in raw milk are killed, and the enzymes lose their activity, which is more suitable for people to drink directly.
Sterilization is to kill all microorganisms in milk, including pathogens, non-pathogens, spores and so on. However, sterilized milk is not aseptic milk, only that the product has reached a commercially aseptic state, i.e. it does not contain pathogenic bacteria and toxins that are hazardous to public health, nor does it contain microorganisms that can multiply during storage, transportation and sale. Therefore, milk can be stored in a stable condition for a long period of time without spoiling.
Common methods of milk sterilization
Among the common pathogenic bacteria in milk, Mycobacterium tuberculosis is more resistant to heat, so the temperature and time of sterilization are based on the effective temperature and time for killing Mycobacterium tuberculosis.
At present, there are three common methods of liquid milk sterilization:
- Low temperature and long time sterilization method, also known as the maintenance method. The specified temperature of 62 ℃ ~ 65 ℃, hold 30 minutes, sterilization efficiency can generally be 99%.
- High-temperature short-term sterilization method. Specified sterilization temperature and time for 72 ℃ ~ 75 ℃, 15 to 16 seconds, or 80 ℃ ~ 85 ℃, 10 to 15 seconds. This method is short, and the sterilization effect is good, some thermophilic bacteria can also be killed.
- Ultra-high temperature instant sterilization method. The specified temperature of 130 ℃ ~ 150 ℃, hold 0.5 ~ 2 seconds. This method of producing sterilized milk with aseptic packaging will be sterilized milk, without refrigeration, can be stored for 3 to 6 months.
The first two belong to Pasteur’s method of disinfection, also known as pasteurization, pasteurization, named after its inventor, the French chemist and biologist Louis Pasteur, is a use of lower temperatures can kill germs, but also maintain the nutrients and flavor of the goods unchanged disinfection method, is now often widely used to define the need to kill a variety of pathogenic bacteria in the heat treatment method.
Application in the dairy industry
Prior to the 19th century, the consumption of dairy products was not widespread and the vast majority of milk was home-produced. Without safe means of sterilization and preservation, milk was a high-risk food. Hygiene during rearing and milking was poor, and raw milk was often contaminated with bacteria. In the hot season, milk would spoil within a few hours, posing a threat to human health.
The invention of pasteurization brought new opportunities to the dairy industry. In the late 19th century, the dairy industry introduced pasteurization, which is widely used in the dairy production process. Pasteurization greatly improved the safety of milk and extended its shelf life. Milk was officially stripped of its “natural” properties and became an industrialized commodity that could be produced and transported on a large scale.
Pasteurization gradually became a common method of manufacturing sterilization and is still widely used to sterilize milk, wine, vinegar, serum protein, and other liquid foods and medicines.
The principle of pasteurization
Pasteurization is one of the moist heat sterilization methods, i.e. boiling water, steam and pressurized steam sterilization.
Temperature is the key factor that affects the growth and inactivation of bacteria. Within a certain temperature range, the higher the temperature, the faster the bacteria multiply and the slower the bacteria multiply. However, if the temperature is too high, the bacteria will die. Different types of bacteria have different optimal growth temperatures and resistance to heat and cold.
The application of pasteurization is actually to use the characteristics of pathogens that are not very heat-resistant, choose the appropriate temperature and holding time to kill all the pathogens in the items while preserving some of the heat-resistant, harmless or beneficial bacteria or bacterial spores.
As there are still some bacteria can survive, pasteurized milk stored at room temperature for a day or two will still be spoiled, so the sterilized milk must be immediately cooled to below 10 ℃ and stored at a temperature of about 4 ℃, so the reproduction of bacteria will be very slow, the nutrition and taste of milk can be kept unchanged in a few days. However, it can only be kept for 3-10 days, up to a maximum of 16 days.
Current pasteurization methods
Current pasteurization methods can be divided into two types: low temperature long time sterilization (LTLT) and high temperature short time sterilization (HTST). Low temperature long time sterilization method takes a long time, the production process is not continuous, long time heat is easy to make some heat-sensitive components change, the sterilization effect is not ideal, has been rarely used, only by small dairy factories used to produce some cheese products. At present, in the large and medium-sized dairy factories use high-temperature short-term sterilization method for the production of pasteurized milk. After pasteurization of milk, all pathogenic bacteria in milk are killed, the small amount of residual microorganisms on the human body is also harmless.
Other sterilization methods
Pasteurization technology also has some shortcomings, such as fruit and vegetable juices and other heat-sensitive food color, aroma, taste, functionality and nutrients have a destructive effect. Therefore, many new non-thermal sterilization technology has been developed.
Non-thermal sterilization technology, which is cold sterilization technology, refers to the use of non-heating methods and methods of food raw materials, products or processing environment of harmful and pathogenic microorganisms killed to achieve the specified degree of sterilization requirements of sterilization technology. Including physical sterilization technology, chemical sterilization technology and natural biocides’ sterilization technology in three categories.
Non-thermal sterilization is generally completed at room temperature, the treatment process does not produce thermal effect or thermal effect is very low, especially suitable for heat-sensitive materials, products and the environment for sterilization.
Our advantages and services
With years of experience in designing and manufacturing pasteurization equipment, we are committed to providing our customers with the best quality products and services. Our equipment is not only efficient and reliable, but also easy to operate and maintain. In addition, we offer customized services to create exclusive pasteurization solutions tailored to our customers’ specific needs.
- High-quality equipment: Manufactured with advanced technology and high-quality materials to ensure equipment stability and durability.
- Customized service: According to the customer’s capacity, location and other conditions, we customize the appropriate pasteurization production line.
- Installation and Training: We provide one-stop service for equipment installation, commissioning, and operation training to ensure that customers can start production smoothly.
- After-sales service: perfect after-sales service system, including equipment maintenance, troubleshooting, etc., to ensure that the customer’s production without worry.
In addition to standard equipment, we also offer customized processing services to create the most suitable pasteurization solutions according to customers’ specific needs and production scale. Whether you are a small family farm or a large dairy processing plant, we can provide the equipment and services to meet your needs.