With the improvement of people's living standards and the strengthening of health awareness, milk has become an indispensable food in our lives. However, many consumers will definitely feel a little confused when buying milk: so many kinds of milk, all kinds of brands, all kinds of flavors, all kinds of packaging and all kinds of prices, which one should they choose? There is nothing wrong with choosing famous brands, and the quality is relatively guaranteed; It is right to have a promotion when buying things. Very economical. However, today we are going to introduce how to know and buy milk through packaging.

Roof bag

When you arrive at the milk monopoly area of the supermarket, you will see a long row of shelves in the freezer neatly arranged with various brands of milk wrapped on the roof. Roof bag, also known as fresh house, is a kind of paper-plastic composite packaging, which looks a bit like a small house. It is filled with pasteurized milk, or pasteurized milk for short. The standard pasteurized milk is that fresh milk is sterilized at 72℃-76℃ for about 15 seconds. Pasteurized milk is a kind of "low temperature sterilized milk". Harmful microorganisms in raw milk are generally killed, but some other microorganisms will remain. Therefore, this milk should be refrigerated at about 4℃ from leaving the production line to transportation, sales and storage to prevent the microorganisms inside from being "active". So pasteurized milk is also called "frozen milk".

The shelf life of pasteurized milk is relatively short, usually about 7 days. The hot weather in the south, especially in summer, is a challenge to pasteurized milk. Consumers must pay attention to the quality of pasteurized milk when buying, storing and drinking it. If the carton is found to be "swollen", it means that the milk has gone bad and must not be drunk. Therefore, special attention should be paid to the preservation conditions when purchasing, and the omission of any link will lead to the rebirth of bacteria and the deterioration of milk.

Paper, plastic bags and glass bottles

These are two kinds of more economical pasteurized milk packaging, because the cost of plastic bags is relatively low and glass bottles can be recycled. This kind of packaged milk, like the roof bag, must be refrigerated and has a short shelf life, usually 2-3 days. These two kinds of packaging are common in door-to-door milk delivery business, so consumers are advised to pay more attention to cold storage. When ordering milk, it is best to choose a company with strong distribution strength, because their cold chain may be more secure. In addition, after the milk is delivered to the door, it must be quickly "cold treated".

Tetra pak brick and tetra pak pillow.

In supermarkets, tetra pak bricks and tetra pak pillows are usually scattered or stacked in boxes. Generally, you can't see these two kinds of packaged milk in the freezer, because tetra pak bricks and tetra pak pillows are packaged at room temperature, which means they can be stored at room temperature.

Milk is so delicate, why can it be preserved at room temperature? It turns out that both tetra pak brick and tetra pak pillow contain "UHT sterilized milk", and some packages say "UHT" processed milk. UHT is actually the abbreviation of ultra-high temperature sterilization. Different from pasteurized milk, ultra-high temperature sterilized milk uses the high temperature of about 134℃ to instantly sterilize raw milk for 4 seconds to kill all harmful bacteria and microorganisms in the milk, and then it is put into aseptic packaging such as tetra pak brick or Tetra Pak pillow under aseptic conditions, reaching the standard of commercial sterility. Tetra pak is a six-layer composite package composed of paper, aluminum and plastic, which can effectively isolate the contact between milk and air, light and bacteria, so it can be stored at room temperature, with a longer shelf life, with tetra pak pillows reaching 45 days and tetra pak bricks reaching 6 to 9 months. Tetra pak milk is also called "normal temperature milk", but some people call it "sterilized milk" or "UHT milk".

Because it can be stored at room temperature, tetra pak milk is very convenient to eat. There is no requirement for refrigeration, and you can drink it anytime and anywhere. However, it should be noted that tetra pak can be stored at room temperature after sealing, but if it can't be eaten after opening, it must be put in the refrigerator for refrigeration.

From a nutritional point of view, although this milk has been sterilized at ultra-high temperature, the sterilization time is very short, only about 4 seconds, so the main nutritional components, such as protein and calcium, are basically not destroyed. Moreover, because the disinfection temperature exceeds 100 degrees Celsius, it can effectively kill all kinds of pathogenic bacteria that may exist in raw milk and ensure the safety of milk to the greatest extent.

Sterile plastic bag

Now you can see a kind of milk in a plastic bag in the supermarket. It looks a bit like milk in paper plastic bags, but its shelf life can reach 30 days. This kind of packaging is a sterile plastic bag that has just been put on the market. Different from pasteurized plastic bags, the UHT milk and packaging materials in them have also been specially treated, so the shelf life at room temperature is greatly prolonged. This kind of packaging is more economical than aseptic paper packaging, but it will break or smell, affecting nutrition and taste. It is recommended to pay special attention to whether the packaging is intact when purchasing.

Speaking of which, you should know something about milk and packaging in the market. Next time you buy milk, please choose according to the characteristics of these packages and your actual situation.