I buy lactose-totally free milk. The sell-by day is usually as a lot as eight weeks from the date of purchase, which is in the community of twice that of constant milk. This appears puzzling; lactose-totally free milk, which still has actually the exact same mass of sugar, has twice as many type of sugar molecules as continuous milk, considering that all the lactose molecules have been separation in to galactose and also glucose. With twice as many sugar molecules per unit volume, one would think lactose-totally free milk would last half as lengthy as constant milk, not twice as lengthy.

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edited Aug 9 "15 at 18:14

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Apparently the process used by manufacturers (ultra-pasteurization) to develop lactose-totally free milk is responsible for the much longer shelf life.

One source reports:

Lactose-totally free milk is pasteurized at a higher temperature than continuous milk. The process, well-known as ultra-pasteurization, is designed to remove the bacteria content completely, offering lactose-complimentary milk a refrigerated shelf-life of 60-90 days, compared via continual pasteurized milk, which retains some bacteria. It has a shelf life of 1-3 weeks.

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A producer (in the United States) of organic dairy products (Organic Valley) defines ultra-pasteurization and the extended shelf-life here as:

Ultra Pasteurization (UP), or Ultra High Temperature (UHT) pasteurization, is the procedure of heating milk to about 280 °F for simply 2 secs and then chilling it back dvery own quickly. The result is milk that"s 99.9% complimentary from bacteria. This pasteurization process creates an extensive shelf-life for milk products of as much as three times the size as HTST pasteurization; while offering the same wholesome, high quality dairy product. This allows us to distribute UP milk products regionally and to other areas of the country that might not have accessibility to our dairy commodities. This is referred to as "ultra pasteurized" on the milk package. Organic Valley supplies its quarts and also some of its fifty percent gallons of milk via Ultra Pasteurization (UP).