UTH cow's milk processing process: cow's milk - heating 80 degrees - steam mixing direct heating 150 degrees - Holding 1-4 seconds - decompression cooling about 80 degrees - homogenization - cooling - packaging
Homogenization is a technique often used in the production of food or chemical industry. Homogenization in food processing
means that the material liquid in the extrusion, strong impact and pressure loss and expansion of the triple action of the material to make the material finer,
so that the material can be more uniformly mixed with each other, such as the use of homogenizer in the processing of dairy products to make the milk
fat crushed more finely, which will make the whole product system more stable. The milk will look whiter. Homogenization is done mainly through homogenizers. It is an important
processing equipment for the food, dairy and beverage industries.
A, milk sterilization In the production process, the general just milked milk first into the milk tank, quickly cooled to inhibit the reproduction of microorganisms, prolong the duration of the antimicrobial properties of milk. The cooled milk needs to be sent to the factory in time for processing. That is, after filtration, purification, cooling, homogenization, sterilization and packaging and other processes, it will become the daily consumption of sterilized milk. Sterilization is an important process in the production of sterilized milk. Generally, it adopts pasteurization method (invented by German microbiologist Louis Pasteur in the 1850s, so it is named as such). This method is divided into two sterilization methods: low temperature and high temperature. Low-temperature sterilization method is to put the milk into a special pasteurizer, heating the milk to 62 ℃ ~ 65 ℃, maintained for 30 minutes; high-temperature sterilization method is to be heated to 73.8 ℃ ~ 76.6 ℃, the duration of 1 to 10 minutes, or 82.2 ℃, the time does not exceed 5 minutes. It is then rapidly cooled to 10°C. The purpose of cooling is to prevent the reproduction of residual sprouts and to maintain the quality of the milk. Alternatively, sterilizing can be achieved by using the earthen method. That is, after cooking over a high fire, a film of milk fat is quickly formed on the surface of the milk (subject to the milk not overflowing), as if a piece of cloth were covering the waves. Calculated from the formation of fat film, cook for another 15 minutes, you can achieve the effect of pasteurization method.
The sterilization of milk must be strictly controlled temperature and time. Otherwise, not only can not achieve the purpose of sterilization, but also destroy the nutrients of milk. This is because: First, a long period of high-temperature boiling will make the milk protein from the sol state into a gel state, resulting in a large number of proteins coagulation and precipitation; Second, the calcium in fresh milk is electrostatically combined with casein, the formation of the human body can be digested and absorbed casein calcium, and a long period of boiling milk and sterilization of milk compared to the casein is about 20% less calcium into more difficult to be absorbed by the human body digestive Calcium salts; three is a long time boiling will also make the lactose caramelization decomposition, low nutritional value; four is the destruction of a variety of vitamins, including vitamin A and other vitamins. Therefore, in principle, sterilized milk should be consumed directly without further boiling. If you need to add heat, just put the bag of cows in 50 ℃ ~ 60 ℃ of hot water for a few moments, it can be.
Second, the preservation of sterilized milk Sterilized milk is not easy to keep at room temperature. Milk is most afraid of sunlight. In the sunlight, milk containing vitamin A, carotene, vitamin B1, vitamin B12 will be destroyed, so it is best to avoid light refrigeration. According to tests, milk cooled to 13 ℃, can be saved for 12 hours, therefore, the temporary non-drinking bags of sterilized milk, can be put into the refrigerator freezer, but do not put into the freezer. Because the milk once frozen, and then heated to dissolve, will occur fat and protein separation, coagulation, precipitation, this time the oil floating, milk flavor talk, nutritional value has also been reduced. If you buy back the milk of individual households, it is best to drink it after boiling and sterilizing, and it is not advisable to keep it. If you want to save, you can use a small mouth container, sealed storage, but not too long.
Sanitizing milk
Milk may contain pathogenic microorganisms such as Mycobacterium bovis, Borrelia burgdorferi, Salmonella
and other miscellaneous bacteria. Bovine tuberculosis bacillus with milk into the human body, can make people suffer from intestinal
tuberculosis and systemic tuberculosis; Brucella can make people infected with brucellosis. Other pathogenic microorganisms in milk
can cause gastrointestinal infections such as acute gastroenteritis. Cows infected with tuberculosis cannot be fed as dairy cows, but sometimes milk from infected cows enters the market because it goes undetected or for other
reasons. One
way a person can become infected with tuberculosis is by drinking milk that contains Mycobacterium tuberculosis. Mycobacterium tuberculosis is an eosinophilic bacillus that does not
form spores, and after leaving the cow's body, it has a very strong ability to survive, and can survive in the natural environment for several
months. Pathogenic microorganisms in milk can originate directly from the cow, but may also be due to
contamination in the external environment, for example, contact with the milker's unclean hands, unclean
milking and milking utensils and packaging materials, can contaminate the milk.
For these reasons, people should not drink raw, unpasteurized milk. This means that it is not safe to drink fresh milk directly from the cow. Bulk milk is
generally unpasteurized and susceptible to contamination from the outside environment, so bulk milk purchased from farmers
must be pasteurized and not consumed directly.
Now, the bags and bottles of milk sold in the market are made by dairy processing companies from the milk
cattle farms and cattle farmers will be purchased after fresh milk, after sterilization processing. Manufacturers use
sanitized milk in two ways, one is high-temperature instant heating method, the temperature reaches 135 ℃; the second is
pasteurization method. Pasteurization involves treating the milk at 62-63°C for 30 minutes, or heating it to 72-73°C for 20 seconds. If packaged and sealed properly, bottled milk can be stored at room temperature for several months to a year after it leaves the factory
and bagged milk has a shelf life of 2-3 days
in summer and 5-7 days in winter.
However, milk sold in the market, despite being sterilized by manufacturers, may still have
product quality problems, or bacteria may be present in the milk due to exceeding the shelf-life, especially in the summer months when temperatures are too high
so it is necessary to re-heat and sterilize purchased bagged
or bottled milk before drinking it.
At home, the methods of heating and sterilizing milk are:
①Pasteurization: this method does not need to boil the milk, and can maximize the preservation of nutrients
Nutritional components, the method is to heat the milk at 63 degrees Celsius for 30 minutes or 73 degrees Celsius for 20 minutes
.
② boiling sterilization method is to put the milk in the pot to boil, but must pay attention to, boil can be
, should not be too long to avoid the loss of nutrients, cooking should also be stirred constantly to
so that it is heated evenly.
3 microwave sterilization method of milk in a glass bottle, placed in the center of the microwave oven, with 650 watts
irradiation, see the milk boiled to stop irradiation. Purchase of milk, heating, such as not immediately eat
use, it is appropriate to place the original pot at room temperature, to drink before, still have to re-heat the process. If you put ice
refrigerated box (4-O ℃), can also extend the retention period, but should not be frozen storage.
A dairy manufacturer surnamed Zhang, a senior engineer said, liquid milk according to the production process can be divided into sterilized milk, sour milk, pasteurized milk three. In terms of sterilization methods alone, there are "pasteurized milk" and "ultra-high-temperature sterilized milk" two. In terms of packaging, can be roughly divided into plastic bags, Tetra Pak, cartons and plastic bottles of four; which Tetra Pak bottle is divided into pillow (bag) and brick type (boxed) two kinds of Tetra Pak, Sweden, produced by the company's 5-7 layers of paper and aluminum foil composite composition of the packaging. According to experts, the shelf life of milk, drinking methods and packaging have a great relationship, different packaging and sterilization methods to determine the shelf life of milk.
Pasteurized (bagged/house-shaped) sterilized milk: also called pasteurized milk. Pasteurized for a few seconds at around 80°C, it is a "short-lived milk" that needs to be stored in a low-temperature refrigerator, with a shelf life of 1-7 days; when stored at temperatures higher than 4°C, the bacteria in the milk can still reproduce, so it cannot be stored for long periods of time at room temperature. Pasteurized milk includes three kinds of products: full-fat and partially skimmed, which are suitable for families who are quick to sterilize and buy more frequently.
Bagged milk is inexpensive and therefore suitable for delivery to thousands of households, becoming breakfast food for many families. The house-shaped fresh milk, which looks like a house, is packaged in light-proof and environmentally friendly paper materials, and adopts the internationally accepted "cold chain control method", which means that the whole process from milk extrusion to production, storage, transportation and sales is carried out under low-temperature conditions, with a preservation period of up to seven days. One of its characteristics is "fresh": from milk extrusion to product filling completed within 8 hours; the second is the production process is advanced, scientific, nutrient preservation, the nutritional indicators are higher than ordinary bagged milk. Strong flavor, rich taste of the house-shaped milk is fresh milk in the boutique, its price after a substantial adjustment began to approach the ordinary people. However, because of the price disadvantage, the house-shaped milk in a considerable period of time is still not able to replace the inexpensive bags of sterilized milk.
Ultra-high temperature (pillow bag/brick box) sterilized milk: also known as high temperature milk. Adopting instant ultra-high temperature sterilization method, in a production line, the sterilization of packaged materials, box forming and packaging is completed at once, i.e., from the package forming to the product filling process, are carried out in a sealed aseptic area. Tetra Pak Fresh cartons contain 5-7 layers of protective film to protect the vitamins in the milk from sunlight. Tetra Pak Fresh packaged UHT-sterilized milk is "long-lasting", with a long shelf life, which allows consumers to buy it less frequently. The product itself does not require refrigeration and has a shelf life of 8 months at room temperature, but only if it is unopened. Once the package is opened, it should be refrigerated and consumed within 3-4 days. Tetra Pak Pillow Pack is economical and more suitable for carrying on the go.