UTH milk processing technology: milk-heating 80 degrees-steam mixing direct heating 150 degrees-heat preservation 1-4 seconds-reduced pressure cooling about 80 degrees-homogenization-cooling-packaging.
Homogenization is a technology often used in food or chemical industry. Homogenization in food processing
It means that the feed liquid is refined under the triple action of extrusion, strong impact and pressure loss expansion.
So that the materials can be mixed with each other more evenly. For example, in dairy processing, homogenizers are used to make milk.
Fat is decomposed more finely, thus making the whole product system more stable. Milk will look more
Add white. Homogenization is mainly carried out by homogenizer. It is the food, dairy and beverage industries.
Equipment to be processed.
First, the disinfection of milk In the production process, the freshly squeezed milk is generally put into a milk tank and cooled quickly to inhibit the reproduction of microorganisms and extend the duration of the antibacterial performance of milk. The cooled milk needs to be sent to the factory for treatment in time. That is, after filtration, purification, cooling, homogenization, sterilization and packaging, it becomes sterilized milk that people drink every day. Sterilization is an important process in producing sterilized milk. Generally, pasteurization is adopted (German microbiologist louis pasteur invented it in 1950s in 19, hence the name). This method is divided into low temperature and high temperature disinfection methods. The low-temperature disinfection method is to put the milk into a special pasteurizer, heat it to 62℃ ~ 65℃ and keep it for 30 minutes; The high-temperature disinfection method is to heat to 73.8℃~ 76.6℃ 1 ~ 10 minute, or 82.2℃ for no more than 5 minutes. Then quickly cooled to 65438 00℃. The purpose of cooling is to prevent the reproduction of residual spores and maintain the quality of milk. In addition, the use of indigenous methods can also achieve the purpose of disinfection. That is, after boiling with strong fire, a layer of milk fat film is quickly formed on the surface of milk (subject to the fact that the milk does not overflow), just like a piece of cloth covering the waves. The effect of pasteurization can be achieved by boiling for 65438 05 minutes from the time when the lipid film is formed.
The disinfection of milk must strictly control the temperature and time. Otherwise, it will not only fail to achieve the purpose of disinfection, but also destroy the nutritional components of milk. This is because: first, boiling at high temperature for a long time will change the protein in milk from sol state to gel state, thus causing a large number of protein to condense and precipitate; Secondly, the calcium in fresh milk combines with casein in an electrostatic way to form casein calcium which can be digested and absorbed by human body, while the casein in milk boiled for a long time is reduced by about 20% compared with sterilized milk, and calcium becomes calcium salt which is difficult to be digested and absorbed by human body; Third, long-term boiling will also make lactose coke and decompose, and its nutritional value is low; Fourth, it destroys many vitamins including vitamin A, so in principle, sterilized milk can be drunk directly without boiling. If heating is needed, just soak the bagged cows in hot water at 50℃ ~ 60℃ for a while.
Second, the preservation of sterilized milk Sterilized milk is not easy to preserve at room temperature. Milk is most afraid of sunshine. Vitamin A, carotene, vitamin B 1 and vitamin B 12 contained in milk will be destroyed under the sunlight, so it is best to store them in a dark cold storage. According to the test, milk can be stored for 65438 02 hours when it is cooled to 65438 03℃. So the bagged sterilized milk that won't be drunk for the time being can be put in the refrigerator, not in the freezer. Because once the milk is frozen and reheated, the fat will be separated from protein and coagulated and precipitated. At this time, the fat will float, the taste of milk will change and the nutritional value will decrease. If you buy self-employed milk, it is best to boil and disinfect it and drink it all at once, so it is not suitable for preservation. If you want to keep it, you can put it in a small container and seal it for a long time.
Disinfection of milk
The pathogenic microorganisms that may be contained in milk include Mycobacterium bovis, Brucella and sand.
Meniere's disease and other miscellaneous bacteria. Mycobacterium bovis enters the human body with milk, which can cause intestinal diseases.
Tuberculosis and systemic tuberculosis; Brucellosis can be transmitted to people. Lactating
Other pathogenic microorganisms can cause digestive tract infectious diseases such as acute gastroenteritis. By rights,
Cows infected with mycobacterium tuberculosis can't be kept as cows, but sometimes they are not found or other.
The reason is that the milk produced by infected cows enters the market. A person infected with tuberculosis
The method is to drink milk containing mycobacterium tuberculosis. Mycobacterium tuberculosis is acidophilic, no.
Spore formation, after leaving cattle, has strong viability and can survive several times in the natural environment.
Month. Pathogenic microorganisms in milk can not only come directly from cows, but also be caused by
Pollution caused by the external environment, for example, touching the dirty hands of the milkman, is unclean.
Milking and milk-holding utensils and packaging materials will pollute milk.
For the above reasons, people can't drink raw milk without disinfection. That is to say,
In other words, it is not safe to drink the fresh milk of cows directly. Bulk milk
Generally, it is not disinfected and is easily polluted by the external environment. Therefore, from agriculture.
Bulk milk purchased by families must be sterilized and cannot be eaten directly.
Now the bagged and bottled milk sold in the market is made from milk by dairy processing enterprises.
Cattle farms and professional cattle farmers buy fresh milk and make it after disinfection. Manufacturer adopts
There are two ways to sterilize milk. One is instantaneous heating at high temperature, and the temperature reaches 135℃. The second one is
Pasteurization. Pasteurization method is to treat milk at 62-63℃ for 30 minutes, or add
Heat to 72-73℃ for 20 seconds. Bottled milk will leave the factory if the packaging is well sealed.
It can be stored for several months to one year at room temperature, and the shelf life of bagged milk in summer is 2-3 days.
5-7 days in winter.
However, although the milk sold in the market has been disinfected by the manufacturer, it will still be produced.
Quality problems of existing products, or due to exceeding the shelf life, especially the high temperature in summer.
It may lead to bacteria in milk, so it is necessary to buy it back in bags before drinking.
Or bottled milk is heated and disinfected.
At home, the methods of heating and sterilizing milk are:
(1) Pasteurization: This method does not need to boil milk, but it can preserve camp to the maximum extent.
The method of cultivating milk is to heat milk at 63℃ for 30 minutes or at 73℃ for 20 minutes.
.
(2) The boiling disinfection method is to boil the milk in a pot, but pay attention to it.
, should not be too long, in order to avoid the loss of nutrients, cooking should also be constantly stirring, so that
So as to uniformly heat.
(3) Microwave disinfection method put milk in a glass bottle and put it in the center of a microwave oven with a power of 650 watts.
Irradiation, stop irradiation when milk boils. Buy back milk, if you don't eat it immediately after heating.
When used, it should be put in the original pot at room temperature and must be reheated before drinking. Such as releasing ice.
Refrigeration in the box (4-O℃) can also extend the shelf life, but it is not suitable for freezing.
A senior engineer surnamed Zhang in a dairy factory said that liquid milk can be divided into sterilized milk, sour milk and pasteurized milk according to the production process. As far as disinfection methods are concerned, there are two disinfection methods: pasteurized milk and ultra-high temperature sterilized milk. As far as packaging forms are concerned, it can be roughly divided into four types: plastic bags, tetra pak, cartons and plastic bottles. Tetra Pak packaging bottles are divided into pillow type (bagged) and brick type (boxed), both of which are made of 5-7 layers of paper and aluminum foil. According to experts, the shelf life and drinking method of milk have a great relationship with packaging, and different packaging and disinfection methods determine the shelf life of milk.
Pasteurized milk: Also called pasteurized milk. Sterilizing at about 80℃ for a few seconds belongs to "short-acting milk" and needs to be preserved at low temperature. The shelf life is usually 1-7 days. When the storage temperature exceeds 4℃, the bacteria in milk will multiply, so it cannot be stored at room temperature for a long time. Pasteurized milk includes whole milk and partially skimmed milk, which is suitable for families with quick disinfection and high purchase frequency.
Bagged milk is cheap, suitable for distribution to thousands of households, and has become breakfast food for many families. House-shaped fresh milk, which looks like a house, is packaged with paper materials that are protected from light and conform to the concept of environmental protection, and adopts the internationally accepted "cold chain control method", that is, the whole process from milk extrusion to production, storage, transportation and sales is carried out at low temperature, and the longest storage period can reach 7 days. One of its characteristics is "freshness": from milk extrusion to product filling in 8 hours; Second, the production technology is advanced and scientific, and the nutritional components are well preserved, and all nutritional indexes are higher than those of ordinary bagged milk. House-shaped milk with rich flavor and mellow taste is a fine product in fresh milk, and its price has been greatly adjusted, and it has begun to approach ordinary people. However, because the price is still at a disadvantage, house-shaped milk can not replace the packaged sterilized milk with good quality and low price for a long time.
Ultra-high temperature (pillow bag/brick box) sterilized milk: also called high temperature milk. Using instantaneous ultra-high temperature sterilization method, the sterilization of packaging materials, packaging box molding and packaging are completed in one production line, that is, from packaging molding to product filling, all in a sealed sterile area. Tetra Pak crisper contains 5-7 layers of protective film, which can protect vitamins in milk from sunlight. The ultra-high temperature instant sterilized fresh milk in Tetra Pak's fresh-keeping packaging is "long-lasting milk", which can make consumers reduce the purchase frequency. The product itself does not need to be refrigerated, and the shelf life is generally 8 months at room temperature, but the premise is that once the package is opened in the unopened state, it should be refrigerated in the refrigerator and drunk within 3-4 days as far as possible. Tetra Pak Pillow packaging is economical and practical, and it is also suitable for carrying out.