Pasteurized milk and UHT are two types of processed milk with a longer shelf life. The main goal of pasteurization is to kill the bacteria that spoil the milk, although there is some debate as to which is better.
Both pasteurized and ultra-pasteurized milk must be refrigerated to prevent spoilage, and both methods ensure that the milk is kept in good condition for much longer and minimizes the risk of spoilage.
What is pasteurized milk?
Pasteurized milk is the type that has been heated to 71ºC for 15 seconds or 62ºC for 30 minutes. The method is called short-term high-temperature treatment. The main goal of pasteurization is to kill bacteria . After this process, the milk is packaged in clean and sterilized conditions. Pasteurized milk should be refrigerated below 7ºC and used as soon as possible to obtain the best quality and flavor after opening the package.
However, some bacteria can still live after heat treatment, but they are very few. These bacteria are not considered harmful and do not spoil milk under refrigerated conditions. The growth of these bacteria occurs later in the lifespan called the past code. Contamination and improper refrigeration cause milk to spoil prematurely.
What is UHT milk?
Ultra-pasteurized milk is milk that is heated to 138ºC for 2 seconds. This method is called ultra high temperature treatment (UHT). The high temperature used here is higher than the temperature used for regular pasteurization. Therefore, ultra-pasteurization kills virtually all bacteria in the milk.
In addition, this milk is packaged in nearly sterilized conditions to avoid contamination. However, it must be refrigerated as it is not canned. Due to the high heat used, ultra-pasteurized milk has a “cooked” taste. The shelf life of this type of milk is 30 to 90 days in refrigerated conditions. After opening, it should be used within 7-10 days and should be kept in the refrigerator at 1 to 3ºC.
Ultra-pasteurization is most often used for dairy products and specialty creams. However, the technique is also becoming popular for plain milk.
Differences and similarities
There are some similar characteristics between both types of milk. For example, the two are two types of processed milk that are subjected to a particular heat for a certain time. In addition, they must be packaged in sterile conditions to avoid further contamination and they must be kept in the refrigerator to prevent spoilage.
Pasteurized milk refers to milk that has been briefly exposed to high temperatures to destroy microorganisms and prevent fermentation, while UHT milk refers to milk that has been processed and sterilized by heating it above 57ºC.
On the other hand, pasteurized milk is treated at 71 ° C for 15 seconds, while ultra-pasteurized milk is treated at 137 ° C for 2 seconds. The method that produces pasteurized milk is called High Temperature Short Time Treatment (HTST), while the method that produces ultra-pasteurized milk is called Ultra High Temperature Treatment (UHT). In the case of pasteurized milk, some bacteria can survive in it, while ultrapasteurized milk is almost sterile.
Pasteurized milk can lose 3-4% thiamine, more than 5% vitamin E, and more than 10% biotin during the heating process, while the whey protein in UHT milk is denatured . Furthermore, recontamination is possible in pasteurized milk, while it is minimized or prevented in UHT milk.
Regarding the materials, the equipment used to produce pasteurized milk is disinfected and can be exposed to the external environment, while the equipment used to produce UHT milk is sterilized and is not exposed to the external environment. Furthermore, the latter’s packaging is treated with H2O2 during packaging.
Pasteurized milk tastes better before 10-21 days, while ultra-pasteurized milk is best before 30-90 days. Pasteurized milk should be used as soon as possible after opening, and UHT can be stored in the refrigerator at 1-3ºC for 7-10 days after opening.
Pasteurized or UHT milk, which is better?
As we have seen, UHT milk is itself pasteurized milk. With the sale of milk in supermarkets, there was great influence and they pressured the dairy industry to offer cheaper milk. The industry responded by switching to a pasteurization protocol that is 120 times faster than the previous one: they heat the milk to 73 ° C, at which they simply have to run it through pipes for 15 seconds. They weren’t interested in maintaining the taste and quality of traditional milk – they just wanted it to be cheaper.
It is important to note that pasteurization at higher temperatures has everything to do with reducing production costs and nothing to do with improving or even maintaining milk quality. Each of the above temperature settings provides milk that has a shelf life of approximately 12-14 days. If we want to store milk for longer, we must use UHT protocols.
UHT is a process that superheats milk under pressure, well above the boiling point. The purpose of this protocol is to render each molecule in the milk inert. Enzymes are destroyed, fungal spores die, etc. There is nothing left in the milk that can cause changes. They will then use an aseptic process for packaging, so that no microbes are introduced at the packaging stage.
The advantages of UHT are clear and all are based on that incredibly long lifespan . On a purely nutritional level, they are identical. Since UHT milk is sterilized and vacuum sealed, it lasts much longer. If we want to use milk to grow bacteria (probiotic drinks: kefir or yogurt), UHT is actually better, as it has no “bad” bacteria to compete with. Also, it tends to taste slightly sweeter.
