How is UHT milk heated to a high temperature for only 1–2 seconds?
I've read that UHT milk is pasteurized by heating the milk to a high temperature (e.g. 135 degrees Celsius / 275 °F) for an extremely short period — around 1–2 seconds.
But this glosses over the question of how quickly the milk cools down — surely the milk doesn't cool down instantly, so it must spend a bit of time at 134, then 133 (271 °F) and so on until it gets down to the temperature of the fridge.
So: how quickly is the milk cooled down, and how do they do it?
Best Answer
According to this product page from Machine Point:
MachinePoint Food Technologies manufactures injection direct heating systems where high pressure steam is injected into pre-heated liquid by a steam injector leading to a rapid rise in temperature between 80 and 145 ºC for 0,5 seconds. Following the product is flash-cooled in a vacuum to remove water equivalent to amount of condensed steam used, until we reach the 80ºC. Then temperature keep been reduced by a heat exchanger.
Physics is fun.
I suspect the various methods are proprietary, depending on what is being pasteurized, but for economy of scale, they are all going to involve a continuous process similar to the one described, where the product enters a heating phase, then very quickly moves into a cooling phase in the machine.
In these continuous types of processes, of course the product will move continuously through all temperatures, but it will do so very quickly.
Pictures about "How is UHT milk heated to a high temperature for only 1–2 seconds?"
How do you heat UHT milk?
The most common methods of UHT heating use steam or superheated water as the heating medium although other less-common electro heating methods can be used. The steam-based methods use steam either directly or indirectly to heat the milk.What temperature is UHT milk heated to?
description. Ultra-high-temperature (UHT) pasteurization involves heating milk or cream to 138\u2013150 \xb0C (280\u2013302 \xb0F) for one or two seconds. Packaged in sterile, hermetically sealed containers, UHT milk may be stored without refrigeration for months.How long is UHT milk heated for?
(UHT) 'ultra-heat treatment' milk or long-life milk is heated to 140\xb0C for two seconds, destroying any harmful bacteria and micro-organisms, which extends its shelf life. It is then packaged in a sterile container.How does high temperature short time pasteurization HTST work?
The most common method of pasteurization in the United States today is High Temperature Short Time (HTST) pasteurization, which uses metal plates and hot water to raise milk temperatures to at least 161\xb0 F for not less than 15 seconds, followed by rapid cooling.Ultra High Temperature (UHT) Treatment l Food Preservation Methods - Lesson 6 l Food Processing
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