Why is it that milk that is instantly sterilized at ultra-high temperature is generally sterilized and canned?

In order to ensure the long-term safety of sterilized milk, it is necessary to use aseptic packaging to package the milk to protect the product from the influence of light and oxygen in the air, so as to effectively inhibit the reproduction of microorganisms in the milk while retaining the original nutritional components of the milk, so that the product can achieve commercial sterility and realize storage and transportation without preservatives and cold chains. Aseptic packaging is a process, including the selection of packaging materials and aseptic filling process. Some careful consumers may have found that the packaging of long-lasting fresh milk is a "green" material composed of paper, aluminum foil and polyethylene plastic layers. This material can effectively prevent re-pollution, but also block the invasion of light, oxygen and microorganisms, thus achieving high-quality, fresh, nutritious and delicious effects. Secondly, the fresh milk that has been sterilized and aseptically packaged by ultra-high temperature (UHT) can be aseptically filled, so that it does not need to be refrigerated during storage and transportation. When the product reaches consumers, its quality and nutritional value are still intact. Even after such a strict process in a fully enclosed environment, UHT milk must pass the heat preservation test process before leaving the factory, which is an internationally accepted UHT milk quality assurance procedure. Processed and produced milk must be stored at 30℃~35℃ for seven days. After the expiration of seven days, once the samples are found to be defective, all products must be detained immediately, and the number of samples should be expanded again, and finally the samples are allowed to leave the factory. So the safety factor of UHT milk is very high.