What is UHT milk?
It comes in a thick cardboard box and can be kept without refrigeration for six to nine months if unopened. Is it really milk?
UHT milk has been available in Malaysia since the 1970s. When it entered the market, it had to jostle with milk powders, condensed milk, evaporated milk and pasteurised milk for a slice of the big milk pie.
Now, 40 years on, UHT milk has not only managed to become a mainstay on supermarket shelves, its consumption has in fact been increasing year on year, reports Dutch Lady Milk Industries Berhad, Malaysia’s leading milk brand and the first company in the country to market milk in UHT packaging.
“We attribute this to the increase in awareness of the benefits of milk, coupled with trends that indicate that a bigger portion of consumers rely on the convenience that UHT packaging offers,” says Aznil Sharizat Mahidin, head of the corporate communications department in Dutch Lady.
“Also, as the socio-economic status of consumers improves, UHT milk is often the preferred choice over family powdered milk,” she adds.
Still, market research indicates that the most popular type of milk consumed in Malaysia is sweetened condensed milk – that’s what goes into our teh tarik.
But what exactly is UHT milk? And how can it last so long without refrigeration?
UHT stands for Ultra Heat Treated or Ultra High Temperature processing – a method of sterilising food by heating it to temperatures upwards of 130°C for a few seconds, and then rapidly cooling it. The procedure is used for sterilising fruit juices, soymilk, soups, ketchup, salad dressings, and particularly, milk.
“Pasteurisation is the minimum amount of processing for milk as required by Australian law and is specified as 72°C for 15 seconds,” explains Michael Ockerse of Pureharvest, one of Australia’s largest organic milk producers. At Pureharvest, UHT milk is processed at 132°C for two to three seconds.
“The increased temperature at which (UHT) milk is treated results in a greater reduction in bacteria and heat-resistant enzymes in comparison to milk that undergoes pasteurisation, giving it an extended shelf life,” explains Amar Srivastava of Australia’s largest milk processor Murray Goulburn, whose company produces Australia’s top UHT milk brand, Devondale, brought in by Pok Brothers Sdn Bhd.
Pasteurised milk and UHT milk are both packed aseptically after the heat treatment, the former in milk cartons, and the latter in Tetra Paks.
“Tetra Pak has seven layers to maintain the quality of milk and reduce bacterial contamination,” explains Srivastava.
The Swedish patented packaging box is made from layers of polyethylene plastic to keep it airtight, foil-laminated to keep out light and thick cardboard layers to provide structural integrity.
The reinforced packaging and the high-heat treatment is the reason UHT milk can sit happily at room temperature until opened (after which it should be treated like any fresh milk: refrigerate and use within a few days), while pasteurised milk must be refrigerated from factory, all through the distribution system to the stores, and finally to your home.
“UHT milk has a nine-month, best-before date, but it is still safe for consumption up till 12 months,” says Ockerse. “Pasteurised milk has a shelf life of only 14 days.”
“There are no preservatives in UHT milk. The long shelf life is guaranteed through high temperature processing and aseptic filling containers,” Sharizat reiterates.
In many parts of the world, UHT milk is still regarded as suspect, if not for the presumed presence of preservatives, then for the effects of the high-heat processing.
“UHT processing does not change the molecular structure of milk,” explains Sharizat. “However, it does change the configuration of the proteins. This process is called denaturation, and is also the reason eggs become hard when boiled and meat becomes firm when cooked.”
UHT milk produced in the early years of the technology’s development was characterised by a strong burnt taste, an effect of Maillard browning caused by the high-heat treatment. But UHT milk production has experienced quantum leaps of improvement since then.
Studies have discovered that by altering the processing parameters of UHT milk, such as using indirect steam injection rather than direct heat application, and increasing the speed at which the milk is cooled after heating, the resulting milk tastes sweeter, and the burnt taste is significantly reduced to the point where it is not discernible to most consumers.
The addition of epicatechin, an antioxidant-rich flavonoid compound abundant in tea and chocolate, has also been found to reduce the “cooked” aroma of UHT milk. But for those wary of additives, a quick check of the label should reveal if there are additives in your milk, and the nutritional content is shown on the pack, too.
“UHT milk has the same nutritional goodness as pasteurised milk, and a similar taste profile,” says Srivastava. “Like fresh milk, UHT milk is a rich source of over 10 essential nutrients, including calcium, phosphorus, potassium, riboflavin, potassium, vitamins A and B12, magnesium, carbohydrate, protein and zinc.”
“UHT processing does not change the nutritional content of milk,” concurs Sharizat, “but it can affect digestive properties, which is mainly of importance to newborns,” and by extension, expecting mothers.
“The only nutrients affected by heat treatment are some of the vitamins, especially vitamin C. This is, however, not present in significant amounts in milk,” says Sharizat. Hence, we don’t usually rely on milk for our intake of vitamin C. “Losses for other vitamins are minimal,” she adds.
“Based on the Malaysian Adult Nutrition Survey published in 2008, we know that protein and vitamin A intake in Malaysia is at the recommended level, but calcium intake is on average only at about 50% of the recommended value. This is a clear indication that Malaysian adults are not consuming sufficient amounts of dairy products,” observes Sharizat.
Did you know? DUE to its long shelf life and high nutritional content, UHT milk is one of the provisions on stockpile in food banks ready to be dispatched for disaster relief.
Glass milk bottles were used in the West as receptacles for the distribution of milk until the 1950s, when they were largely replaced with milk cartons.
The rotary milking machine, one of two types of modern mechanisms for harvesting milk, the other being the herring bone milking machine.
Safe to glug: UHT milk is packed aseptically into the sevenlayered Swedishpatented Tetra Pak to maintain its long shelf life.