i buy lactose-free milk. The sell-by date is generally as much as eight weeks native the date of purchase, which is in the neighborhood of twice that of continual milk. This appears puzzling; lactose-free milk, i beg your pardon still has actually the very same mass that sugar, has twice as countless sugar molecule as regular milk, due to the fact that all the lactose molecules have actually been separation in come galactose and also glucose. V twice as countless sugar molecules per unit volume, one would think lactose-free milk would last half as lengthy as continuous milk, not twice as long.

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Apparently the procedure used by manufacturers (ultra-pasteurization) to produce lactose-free milk is responsible because that the much longer shelf life.

One source reports:

Lactose-free milk is pasteurized at a higher temperature than consistent milk. The process, known as ultra-pasteurization, is draft to eliminate the bacteria contents entirely, giving lactose-free milk a refrigerated shelf-life of 60-90 days, compared with continual pasteurized milk, i beg your pardon retains part bacteria. It has actually a shelf life the 1-3 weeks.

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A producer (in the united States) of necessary dairy assets (Organic Valley) explains ultra-pasteurization and also the expanded shelf-life here as:

Ultra Pasteurization (UP), or Ultra High Temperature (UHT) pasteurization, is the process of heater milk to around 280 °F for just 2 seconds and also then chilling it ago down rapidly. The result is milk that"s 99.9% free from bacteria. This pasteurization process creates prolonged shelf-life because that milk commodities of increase to three times the size as HTST pasteurization; while offering the exact same wholesome, quality dairy product. This permits us to distribution UP milk assets regionally as well as to other areas of the country that can not have accessibility to our dairy products. This is referred to as "ultra pasteurized" top top the milk package. Organic Valley offers its quarts and some the its half gallons the milk v Ultra Pasteurization (UP).