How is milk made? Whether you're raising dairy cows or simply enjoy a cold glass of milk, you'll want to know about the journey milk takes from the farm to the bottle or carton.
It All Starts with Cows
Milk comes directly from cows. The cows are milked with a milking machine. The milk is piped from the milking machines to a large, refrigerated, stainless-steel holding tank. It is then pumped into tanker trucks to be transported to the processing plant.
Once at the processing plant, the milk goes to a separator machine or a clarifier. Both machines spin the milk through conical disks. The clarifier removes debris in the milk, including sediment and some bacteria. The separator does the same thing, but it also separates the milk fat from the milk. The separator produces skim milk, 1% milk, 2% milk and cream. The lower-fat-content milks are made by skimming milk from the top of the separator. Milk with higher fat content weighs more than lower-fat milk, so it rises to the top during processing.
Fortification and Pasteurization
Once through the clarifier or separator, the milk is fortified with vitamins A and D. The vitamins are added with a peristaltic pump. The milk is then pasteurized. Pasteurizing kills bacteria in the milk that could cause health problems in people. The milk is heated to 161 degrees Fahrenheit for 15 seconds, then sent to a homogenizer.
Once pasteurized, the milk is homogenized. This reduces the size of the milk-fat particles, which prevents the milk fat from separating. If the solids separate, they float to the top as cream. To homogenize the milk, it is pressurized to 2,500 to 3,000psi by a piston pump, then forced through small passages. After this process, the milk is quickly cooled to 40 degrees Fahrenheit. The milk is now ready to be packaged for retail sale.
Almost all milk that is sold in supermarkets goes through this process, although a few states do allow the sale of raw milk, which has not been pasteurized. Milk that has been processed will be labeled; look for the words "pasteurized" and "homogenized" on the package. Homogenization isn't required, but most dairies use this process to keep milk from separating.
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