Yeast Science: Can Yeast Inflate a Balloon?

Yeast are one-celled fungi that multiply by "budding". They multiply quickly, and as they grow they produce carbon dioxide. Because of this special attribute, yeast is very important in baking and fermenting—we wouldn't have bread without it! In this simple experiment, you'll get to know this fascinating micro-organism, learning what it likes to eat and just how gassy it can get.

What You Need:

• 3 packages of yeast
• Warm water (about 90°-110° F)
• 3 clear, 16 ounce plastic water or soda bottles
• Funnel (or steady hand to pour the yeast into the bottles)
• 3 balloons
• Rubber bands
• 3 different kinds of sugary liquids, such as cola, apple juice or orange juice, and corn syrup, warmed to 90°-110° F (corn syrup at room temperature is ok)

What You Do:

1. Pour one package of yeast into each of the bottles, then fill each bottle 1/4 full with warm water. Make sure you use warm water between 90°-110°; water that is too cold or too hot will kill the yeast.
2. Fill each bottle halfway with a different sugary liquid. Be sure to label each bottle with the liquid it contains.
3. Place a balloon over the mouth of each bottle and secure in place with a rubber band.
4. The yeast will begin to multiply immediately. Wait a few hours or even a day to see how your balloons inflate. The balloon that inflates the biggest will tell you which liquid the yeast liked the most!

Did You Know?

• As yeast grows and expands in bread dough, it creates pockets of carbon dioxide that set in the oven, giving the finished loaf a springy, spongy texture.
• We don't know when yeast was first used in bread making, but we do know that the ancient Egyptians were the first to use it.