Everyone knows that the milk you find at grocery stores comes from cows. But have you ever thought about what happens to milk from the time it leaves the cow to the time you pour it into your glass?
One place to find out is at Homeland Creamery. It's a small family-run dairy and milk plant in North Carolina.
Most dairies ship their milk to another location to be processed. But at Homeland Creamery, Chris and David Bowman have been processing and bottling milk on their own farm since 2001.
The brothers are the sixth generation of their family to farm the same land. They process and bottle milk from their cows three days a week.
"On bottling days, we're able to get milk that came out of the cows that morning on the store shelf that same morning," Chris Bowman says.
The first step is to milk the cows. At Homeland Creamery, that's done twice a day, early in the morning and in the afternoon. Automatic milking machines take the milk directly from the cows' udders to a storage tank, where it is kept at a temperature of 37 to 39 degrees F.
Next they have to decide what kind of milk they want to produce that day. The Bowmans make whole, skim, low-fat, and chocolate milk, as well as buttermilk. During the winter, they also make eggnog for the holidays.
All of the processing work takes place in the milk plant. That's a separate building from the milking parlor (the building where the cows are milked).
If it's time to bottle whole milk, the first thing that happens once the milk is pumped into the plant is pasteurization.
In this process, milk is heated to kill bacteria and other microorganisms. It also makes milk stay fresh longer.
Many large milk plants use a method called high-temperature, short-time pasteurization. That means the milk is heated to a high temperature for a just a few seconds and then cooled.
Homeland Creamery uses a different technique because its processing equipment is from the 1950s.
Its method is called vat pasteurization. And it involves the slow heating of milk in large vats to 150 or 155 degrees F. over a period of about 40 minutes.
The vats are round, stainless-steel tanks whose walls are designed to allow hot steam to pass through them. The steam heats the inside walls of the tanks, and that warms the milk.
In the center of each tank is a big mixing paddle that stirs the milk to make sure it all comes in contact with the outer walls and gets evenly heated.
From the pasteurizing vats, milk is pumped to a homogenizer. That's a large, squat machine that blends cream particles into the rest of the milk.
Normally, whole milk contains between 4 and 5 percent cream. Without homogenization, that cream would rise to the top of a container of milk because it's less dense.
"The homogenizer breaks down the fat molecules in the cream," Chris explains.
It does this through a motor that drives a set of pistons that pump back and forth like the pistons in a car engine.
The pistons help pump the milk in high-pressure streams of 2,000 pounds per square inch through small tubes. This causes the larger fat molecules in the cream to break into smaller molecules. They become heavier and then are no longer able to float to the top.
If the Bowmans aren't processing whole milk, however, they don't want that cream in the milk in the first place. To make low-fat or skim milk, they separate the cream from the milk before pasteurization using in a machine called a cream separator.
"It's a giant centrifuge," Chris says. "Whole milk goes in, and out comes 60 percent skim milk and 40 percent cream."
The separated cream is pasteurized, but not homogenized. Then it is bottled individually for sale as cream. Or it may be mixed with milk to make half-and-half. Another option is to keep the cream to churn it into butter, or use it to make ice cream.
After the cream is removed, skim milk is processed just as whole milk is.
When making chocolate milk, eggnog, or ice cream, the Bowmans add the extra ingredients to the milk in the pasteurizing vats. (That's also where Vitamin D is added to the milk, as required by law.)
After pasteurization, the tasty mixtures are homogenized just like milk. One exception to this rule is ice cream, which is homogenized at a higher pressure because it is thicker than milk.
Homogenized ice cream is then transferred to machines that stir the mixture at cold temperatures until it freezes. These machines work in much the same way as the ice-cream-makers that some people have at home – although the ones at the creamery are much larger!
Milk is bottled by a machine that can be adapted to handle various sizes of containers – gallons, half-gallons, quarts, and pints. Once the milk is bottled, it's stacked in crates and taken to cool storage to be delivered to local stores, restaurants, coffeehouses, and bakeries.
The Bowman brothers take turns managing the milk plant. One week Chris is in charge, while David manages the cows and the fields. Then they switch.
On bottling days, the work starts while you're still asleep in bed: One of the Bowmans has to get up by 2 a.m. – sometimes at midnight – to start processing milk!
Around 5 a.m., two employees come in to help, and the three of them process milk until around 11 a.m. Then it's time to freeze ice cream, make butter, or help out with the other farm chores. Sometimes they can squeeze in a short nap.
The old-fashioned equipment at Homeland Creamery works slowly compared with the modern equipment at today's larger milk-processing plants.
But the extra effort comes with an extra benefit, David explains. "Vat-pasteurized milk tastes richer and creamier than other milk."
"I've had [older] people tell me our milk tastes like milk used to when they were growing up," Chris says."
"We make milk the way it used to be made," David says, "and our milk tastes the way it used to taste."