On Food and Cooking

pasteurization to catch on in the dairy.
Nowadays, in industrial-scale production, it’s
a practical necessity. Collecting and pooling
milk from many different farms increases the
risk that a given batch will be contaminated;
and the plumbing and machinery required for
the various stages of processing afford many
more opportunities for contamination.
Pasteurization extends the shelf life of milk
by killing pathogenic and spoilage microbes
and by inactivating milk enzymes, especially
the fat splitters, whose slow but steady
activity can make it unpalatable. Pasteurized
milk stored below 40ºF/5ºC should remain
drinkable for 10 to 18 days.
There are three basic methods for
pasteurizing milk. The simplest is batch
pasteurization, in which a fixed volume of
milk, perhaps a few hundred gallons, is slowly
agitated in a heated vat at a minimum of
145ºF/62ºC for 30 to 35 minutes. Industrial-
scale operations use the high-temperature,