Peggy visits a dairy farm and a milk processing plant to learn how milk gets from a cow to the store.
You may have heard milk described as "nature's most perfect food." That's because it contains three main nutrients--protein, calcium, and riboflavin--essential for bones and teeth to grow, body tissues to repair themselves, and antibodies to form.
Milking techniques and milk processing have changed a lot since Christopher Columbus brought the first cattle to the Western Hemisphere in 1493. Advancements such as automatic milking machines and computers have improved milk production, safety, and availability.
Milk production begins with the cow. A mature cow eats, on average, 50 pounds of silage and drinks 25 to 50 gallons of water a day. A cow initially chews just enough to swallow. The food goes into the first chamber (called the rumen) of its four-part stomach. Later, the cow burps up small amounts of food and chews it again. The food then goes into the next chamber (reticulum) before passing through the final two chambers (abomasum and omasum), where bacteria and stomach acids work on it. Food provides cows with protein, energy, vitamins, minerals, and bulk. It is also the raw material that makes milk. However, to begin producing milk, a cow must first give birth. The hormones released at birth and the sucking of the calf stimulate the cow to lactate (produce milk) for her calf. Cows produce the greatest amount of milk right after they give birth. If a cow is not milked, she will stop producing milk.
Milk is made and stored in the cow's udder, which is divided into four separate quarters, each having its own milk supply. When laden with milk, each section can be drained through one teat. First the farmer spray-washes the cow's udder with a warm iodine solution to control diseases. The milking machine cups are then attached and draw the milk from the udder into a system of pipes that transports the warm milk to a large storage tank for cooling. This milk is known as raw milk.
A trucker comes to the farm to collect and transport the raw milk to a processing plant. At the plant, milk is tested for acceptable levels of bacteria, and pasteurized by heating it to 77*C (170*F), then cooling it. This kills any harmful bacteria that may be in the milk.
During processing, butterfat is skimmed from the milk. The butterfat is then forced through small holes. This breaks it up into very tiny globules which will stay mixed evenly with the milk. Butterfat is then added back into the milk in proper proportions to produce skim, 2%, whole, and other types of milk. This process is called homogenization.
Once homogenization is completed, the milk goes into big storage tanks where it is cooled. It is agitated and then put into bottles or cartons for delivery. The total time from cow to shelf is 48 to 96 hours!
The amount of milk needed to create different products varies. With the following information, organize and construct a data table to show how much milk is needed to produce some of these foods. Clue: One quart of milk weighs 2.15 pounds.
To make one pound of you need
Visit a dairy farm. What did you enjoy most? What did you like least? Would you like to live on a dairy farm?
Interview a veterinarian or dairy farmer. Develop a series of questions to ask your interviewee. For example, what kinds of illnesses do cows get? What is a cow's normal temperature? What does he or she do when a cow gets sick? How much do cows sleep?
Make ice cream with a ice cream maker. Show how the ice cream forms. Explain the chemical and physical principles behind it.
Research one of the following men and women to find out their contribution to milk production: Louis Pasteur, Harvey D. Thatcher, Henry L. Coit, S. M. Babcock, Gail Borden, and Dolly Madison.
Compare the nutritional value of soft drinks and milk. How do other food products compare nutritionally to milk? Develop a chart to show these values.
Newton's Apple is a production of KTCA Twin Cities Public Television.
Made possible by a grant from 3M.
Educational materials developed with the National Science Teachers Association.