Ultra-high-temperature processing

The most commonly applied technique to provide a safe and shelf-stable milk is heat treatment. The first system involving indirect heating with continuous flow (125 °C [257 °F] for 6 min) was manufactured in 1893. In 1912, a continuous-flow, direct-heating method of mixing steam with milk at temperatures of 130 to 140 °C (266 to 284 °F) was patented. However, without commercially available aseptic packaging systems to pack and store the product, such technology was not very useful in itself, and further development was stalled until the 1950s. In 1953, APV pioneered a steam injection technology, involving direct injection of steam through a specially designed nozzle which raises the product temperature instantly, under brand name Uperiser; milk was packaged in sterile cans. In the 1960s APV launched the first commercial steam infusion system under the Palarisator brand name.[7][8]

Shelf-stable UHT milk carton (on right)

In Sweden, Tetra Pak launched tetrahedral paperboard cartons in 1952. They made a commercial breakthrough in the 1960s, after technological advances, combining carton assembling and aseptic packaging technologies, followed by international expansion. In aseptic processing, the product and the package are sterilized separately and then combined and sealed in a sterile atmosphere, in contrast to canning, where product and package are first combined and then sterilized.[9]

The Importation of Milk Act 1983 was passed by the UK Parliament following a successful appeal to the European Court of Justice that prevented the government from banning the importation of UHT milk.[10]

In June 1993, Parmalat introduced its UHT milk to the United States.[11] 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.[6] UHT milk is also used for many dairy products.

In 2008 the UK government proposed to produce 9 pints out of every 10 as UHT by 2020[12] which they believed would significantly cut the need for refrigeration, and thus benefit the environment by reducing greenhouse gas emissions.[13] However the milk industry opposed this, and the proposition was abandoned.

Ultra-high-temperature processing is performed in complex production plants, which perform several stages of food processing and packaging automatically and in succession:[14]

• Flash heating
• Flash cooling
• Homogenization
• Aseptic packaging

In the heating stage, the treated liquid is first pre-heated to a noncritical temperature (70–80 °C [158–176 °F] for milk), and then quickly heated to the temperature required by the process. There are two types of heating technologies: direct, where the product is put in a direct contact with the hot steam, and indirect, where the product and the heating medium remain separated by the equipment's contact surfaces. The main goals of the design, both from product quality and from efficiency standpoints, are to maintain the high product temperature for the shortest period possible, and to ensure that the temperature is evenly distributed throughout.[14][15]

UHT milk has seen large success in much of Europe, where across the continent 7 out of 10 people drink it regularly.[17] In countries with a warmer climate such as Spain, UHT milk is preferred due to the high cost of refrigerated transportation and "inefficient cool cabinets".[18] 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, due to legislation and societal attitudes.[19]

While most regular milk sold in the United States is pasteurized, a significant share of organic milk sold in the US is UHT treated (organic milk is produced at fewer locations and consequently spends more time in the supply chain and could therefore spoil before or shortly after being sold if pasteurized).[6]

Consumption of UHT milk in Europe as a percentage of total consumption, as of 2007[13]

Country	percent
Austria	20.3
Belgium	96.7
Croatia	73[20]
Czech Republic	71.4
Denmark	0.0
Finland	2.4
France	95.5
Germany	66.1
Greece	0.9
Hungary	35.1
Ireland	2.1
Italy	49.8
Netherlands	20.2
Norway	5.3
Poland	48.6
Portugal	92.9
Slovakia	35.5
Spain	95.7
Sweden	5.5
Switzerland	62.8
Turkey	53.1
United Kingdom	8.4

Capsules of UHT milk

UHT milk contains the same amount of calories and calcium as pasteurized milk. Some loss of vitamin B₁₂, vitamin C, and thiamin can occur in UHT milk.[21] UHT milk contains 1 μg of folate per 100 g, while pasteurized milk contains 9 μg.[4]

UHT milk's protein structure is different from that of pasteurized milk, which prevents it from separating in cheese making.[22]

Two studies published in the late 20th century showed that UHT treatment causes proteins contained in the milk to unfold and flatten, and the formerly "buried" sulfhydryl (SH) groups, which are normally masked in the natural protein, cause extremely-cooked or burnt flavours to be sensed by the human palate. One study reduced the thiol content by immobilizing sulfhydryl oxidase in UHT-heated skim milk and reported, after enzymatic oxidation, an improved flavor.[5] Two US authors prior to heating added the flavonoid compound epicatechin to the milk, and reported a partial reduction of thermally generated aromas.[23]

• Aseptic processing
• Food preservation
• Food storage
• Food packaging
• Food engineering
• Pasteurization
• Flash pasteurization

• Milk in a Box – Losing the bottle at the Wayback Machine (archived 2017-04-02) From: Interesting Thing of the Day