How pasteurized milk is made

Milk is flash-heated for 15 seconds and chilled again, killing disease germs and not the taste.

stations: 6
things upstream: 1
raw source: 1
step from the ground: 1

The short version

Raw milk is cooled on the farm and trucked to a dairy. There a centrifuge separates the cream, which is added back to set the fat level. Then the milk is homogenized and pasteurized, usually at 72 °C for 15 seconds, cooled fast and bottled. Kept cold, it stays fresh for up to three weeks.

Milk and chill on the farm

Cows are milked by machine and the milk goes straight into a cooled tank. Cold slows the bacteria that would sour it.

Goes in
Raw milk
Test it at the dairy

Tankers deliver milk to a dairy, where each load is sampled for fat, protein, temperature and antibiotics before it is allowed into the silos.
Spin out the cream

Fresh milk will separate into cream and skim milk by itself after 12 to 24 hours. A centrifugal separator does it in moments, and the dairy puts back exactly as much cream as it needs for full cream, reduced fat or skim milk.
Break up the fat globules

In homogenization the milk is pumped at high pressure through narrow gaps. Turbulence breaks the fat globules into smaller droplets, so cream stays mixed in and no layer forms on top.
Heat it briefly

In the standard high-temperature short-time process, a stack of steel plates heats the milk to 72 °C for 15 seconds. A plate on the other side lets cold incoming milk soak up the heat from the outgoing milk, which saves energy.

72 °C for 15 seconds
Chill and bottle

The milk is cooled right away and filled into cartons or jugs. Dairies print a best before date on every one.

End of the linePasteurized milk Next it goes into cheese, yogurt, ice cream and 4 more.

Worth repeating

Louis Pasteur developed his gentler heating method during an 1864 summer holiday, to fix acidic wine.
Ultra-high-temperature treatment heats milk to 135 °C for just 1 to 2 seconds.