Here we have gathered some of the most frequently asked questions about Ultra-High Temperature (UHT) Milk. We hope that you will find all the answers you might have when it comes to UHT Milk.
What is UHT milk and how is it different from “fresh milk” and raw milk?
UHT milk is milk that has been processed at ultra high temperature (UHT). The sterilisation is made through rapid heating of milk to a temperature of at least 135°C, keeping it there for a few seconds, and then quickly cooling it down to ambient temperature. Such treatment results in that all microorganisms present in the raw milk are killed. When packaged into aseptic containers, UHT milk has a shelf life of many months and doesn’t need to be refrigerated until the package is opened. The shelf life of UHT milk is not limited by growth of microorganisms but instead by physical, chemical and enzymatic changes in the milk, such as browning reactions, cream separation, sediment or gel formation. “Fresh milk” is often used by consumers to describe milk that is distributed under chilled conditions. This usually refers to pasteurized milk, which means the milk that has been heated at 72-74°C for 15-20 seconds. Pasteurization kills all pathogenic (disease causing) microorganisms in the raw milk. To limit the growth of the remaining spoilage micro - organisms, pasteurized milk needs to be kept under chilled conditions throughout the distribution and storage. The shelf life of pasteurized milk depends on the initial load of microorganisms as well as storage temperature but is normally around 7 days. Raw milk refers to the milk produced by cows (or other animals) without processing. Drinking raw milk can cause serious diseases, as it can harbour dangerous microorganisms. According to the Food and Drug Administration (FDA), between 1993 and 2006 more than 1500 people in the United States became sick from drinking raw milk or eating cheese made from raw milk. For this reason, in many countries, all milk products sold in retail outlets must be pasteurized or UHT treated. In some markets, consumers buy raw milk and boil it at home. This makes the milk safe to drink but it is hard to control the process to maintain the quality.
How long has UHT technology existed?
The birth of sterilised treatment as a means of preserving food began in France in the early 1800s. The food was filled in tin-coated steel containers which were placed in pressurised chambers, (auto - claves), in which they were heated to 110-125°C for 30-40 minutes. This process is called “in container sterilization”. In the late 1950’s, building on this earlier food conservation technology, Tetra Pak Processing Systems (Alfa Laval at the time) pioneered its own continuous UHT process. By using higher temperatures and shorter times it achieved the same effect in killing micro - organisms, while being much gentler towards changes to taste and colour of the milk. Together with Tetra Pak’s innovation of the aseptic package, this kick-started the growth of the UHT milk segment.
Are there any preservatives used in UHT milk?
The ultra-high heat treatment used in the production of UHT milk kills all microorganisms. The milk is then packed in an aseptic package that protects it from entrance of any microorganisms, making it safe for months without need of refrigeration. There is simply no need to add preservatives into a UHT treated product, as there are no microorganisms growing. Aseptic containers also protect the product from air and light, thereby protecting the product quality.
Does UHT milk taste different from fresh milk? And why?
UHT milk may taste slightly different from pasteurized milk due to the treatment at a higher temperature. The taste of UHT milk is often described to be more cooked, richer and creamier compared to pasteurized milk. But the difference is minor when the milk is served at the same temperature - some people may notice while others do not.
What are the nutritional / health benefits of UHT milk?
There are many health benefits of milk, and they are very similar for both pasteurized and UHT milk. These are: • Milk contains a range of nutrients that are only found together naturally in dairy sources. • Milk is high in calcium and other nutrients required to build strong bones and teeth. • Milk is a very important source of dietary calcium. About 75% of calcium intake comes from consuming dairy products. • Milk contains high-quality protein and essential amino acids, which are needed to build and maintain muscle. • Milk contains nutrients and micronutrients (for example vitamin A, vitamin B12 , phosphor, iodine and potassium) that are essential to health and play a role in nerve and muscle function, energy release, vision, blood clotting and red cell formation, digestion, blood pressure, skin health, the immune system, psychological function and growth. • Other health benefits include weight control, protection against cardiovascular disease, lowering blood pressure and the prevention of Type 2 diabetes. • Designed by nature, milk’s exceptional nutritional content makes it a highly nourishing beverage and well-rounded food source.
Is UHT milk less nutritious than fresh milk?
The nutritional value of UHT milk and fresh milk are the same when it comes to the main nutrients in milk, such as protein, calcium and Vitamin D. UHT treatment may reduce the level of some heat sensitive nutrients such as vitamin C, but milk is not the main source of these nutrients in the first place. The storage time also has an influence since some nutrients may degrade with time.
Does UHT milk contain calcium?
Yes of course. The nutritional value of UHT milk and fresh milk are the same when it comes to the main nutrients in milk, such as protein, calcium and Vitamin D.
Are the probiotic bacteria killed during the UHT process? Does the absence of probiotic bacteria cause problems in your intestine? Is milk a probiotic source?
Neither regular pasteurized milk nor regular UHT milk contain probiotic bacteria. However they can be added in a special form before or after the heating process. In such case it will and in case of UHT milk with probiotic the product is stored in refrigeration to regulate the status of the probiotics. There are several fermented products with probiotic - like for example yoghurts on the market. In these products probiotic bacteria are added as an important part of production steps.
Is homogenization used in UHT/pasteurized unhealthy? Does the very high pressure change the protein structure to make it unhealthy?
Homogenization is a mechanical treatment where the milk passes through a narrow gap at a high velocity. This treatment reduces the size of the fat droplets postponing the time for creaming to take place. Homogenization is used to ensure product quality and consistency for all packaged milk, including UHT and pasteurized milk. The pressures used are normally around 200 bar. Most studies investigating the healthy aspects of milk are conducted using homogenized milk, so the homogenising effect is included in the total judgement.
How long can I keep UHT milk for? How?
UHT milk can be kept for months unopened, but the easiest way is to check the shelf life marked on the package. Once opened it must be refrigerated and will last for another few days. UHT milk does not require refrigeration until it has been opened. Once opened, it is recommended that the milk should be refrigerated and consumed quickly like any other perishable food.
Can UHT milk be chilled?
Yes, you can if you want to store and drink it chilled, though UHT milk does not require refrigeration for storage until it has been opened.
Can UHT milk be frozen?
Yes, you can freeze and unfreeze any milk. However, the flavour and the texture of the milk may be affected.
Is powdered (dried) milk made from UHT milk or fresh milk?
Milk powder is made from fresh milk which is concentrated , and thereafter dried. The spray drying process involves ‘introducing’ the milk concentrate into a chamber through which hot air is circulating. The remaining water then evaporates from the droplets of concentrated milk, leaving a fine powder.
Can UHT milk be organic?
Yes it can be. In fact, about 80% of the organic milk sold in the U.S. is UHT processed. This is because organic farms are not in every region of the country, and organic milk needs to travel even farther for many markets.
Why does the shelf life specified on different brands of UHT milk differ?
With the aseptic technology, UHT milk should be safe for consumption for many months when stored under normal conditions. The shelf life specified on the product indicates the period of time during which the manufacturer guarantees its quality and safety. The length of the shelf life largely depends on the product formulation and climate, but is also affected by a number of other factors, such as regulatory requirements of a market, the company’s sales strategy, and consumer preference.
What is aseptic packaging?
Aseptic packaging is a procedure consisting of sterilization of the packaging material or container, filling with a commercially sterile product in an aseptic environment, and producing containers that are tight enough to prevent re-contamination, i.e. hermetically sealed.
What does it do?
For products with a long non-refrigerated shelf life, the package must also give almost complete protection against light and atmospheric oxygen in order to protect the nutritional value and product sensory.