Ultra-high temperature processing (UHT), or ultra-heat treatment, sterilizes food by heating it above 135°C (275°F) - the temperature required to kill spores in milk - for 1 to 2 seconds. UHT is most commonly used in milk production, but the process is also used for fruit juices, cream, soy milk, yogurt, wine, soups, honey, and stews. UHT milk was first developed in the 1960s and became generally available for consumption in the 1970s.
The heat used during the UHT process can cause Maillard browning and change the taste and smell of dairy products. An alternative process is HTST pasteurization (high temperature/short time), in which the milk is heated to 72°C (161.6°F) for at least 15 seconds.
UHT milk, if not opened, has a typical unrefrigerated shelf life of six to nine months. Flash pasteurized milk has a shelf life of about 12 months, and pasteurized milk about two weeks from processing, or about one week from being put on sale.
- UHT and pasteurized milk contains the same amount of calcium.
- UHT milk's protein structure is different from that of pasteurized milk, which prevents it from separating in cheese making.
- Some nutritional loss can occur in UHT milk.
UHT milk has seen large success in much of Europe, where across the continent as a whole 7 out of 10 Europeans drink it regularly. In fact, in a hot country such as Spain, UHT milk is preferred due to high costs of refrigerated transportation and "inefficient cool cabinets". UHT is less popular in Northern Europe and Scandinavia, particularly in Denmark, Finland, Norway, Sweden, the United Kingdom and Ireland. It is also less popular in Greece, where fresh pasteurized milk is the most popular type of milk.
In June 1993, Parmalat introduced its UHT milk to the United States. In the American market, consumers are uneasy about consuming milk that is not delivered under refrigeration, and reluctant to buy it. To combat this, Parmalat is selling its UHT milk in old-fashioned containers, unnecessarily sold from the refrigerator aisle. Almost all the organic milk, and the majority of non-organic milk, available in American supermarkets is UHT processed. UHT milk is also used for many dairy products.
UHT milk is sold on American military bases in Puerto Rico and Korea due to limited availability of milk supplies and refrigeration.
UHT milk gained popularity in Puerto Rico as an alternative to pasteurized milk due to environmental factors. For example, power outages after a hurricane can last up to 2 weeks, during which time pasteurized milk would spoil from lack of refrigeration.
In 2008 the UK government proposed a 90% UHT milk production target by 2020 which they believed would significantly cut the need for refrigeration, and thus benefit the environment by reducing green house emissions. However the milk industry opposed this, and the proposition was abandoned.
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