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Exploration of the Month

January 1999

yogurt disappearing


Every day, many people enjoy yogurt for part of a meal or as a midday snack. In America, yogurt is produced from cow's milk. Yogurt is popular all over the world, but it comes from the milk of different animals. In Turkey and Greece, sheep's and goat's milk is used and Egypt gets its yogurt from an animal called the water buffalo. Some of these different varieties can be found at your local store. You could try food that children halfway across the globe enjoy.

Yogurt is produced in special factories around the world. Milk solids are added to the cow's milk to give it a custard like thickness. Then a mixture containing special bacteria is poured into the milk. Pictures of this lactic acid bacteria can be found below. The mixture is raised in temperature to about 110 degrees Fahrenheit, or 43 degrees Celsius, for approximately five hours.

Image of stained bacillus L. Bulgarius

The bacteria acts like a yeast: as the milk heats, a substance called curd forms. Curd is resembles the hard chunks which appear in milk after the expiration date. The yogurt is then slowly cooled and possibly fruits are added. Below is some pictures of the fruit found within a sample of strawberry yogurt. The pictures in the center and the left have measurement bars marking 100 and 25 micrometers, respectively. It is amazing to see the individual cells from this fruit specimen!

strawberry, regular size strawberry, 10X strawberry, 50X

Yogurt has been made for thousands of years, although the process of making it was not as refined as it is today. A good page on the history of yogurt is provided by http://www.yaourt.org. One day someone explored the possibility of using bacteria to create different types of food. Don't be alarmed though about the bacteria in yogurt. Everyone has bacteria inside their bodies; especially in the stomach and intestines where food is broke up and digested. When you eat yogurt, it encourages the good types of bacteria to multiply in your digestive track. These "friendly" bacteria also protect our system against harmful microorganisms which cause tummy aches and infection. An animated view of the bacteria contained in yogurt is shown below.

animation of yogurt bacteria

Yogurt is awesome food! It's good and good for you!

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Last Updated: 7/10/98