Barf Bag Microbiology

Introduction:

Yeast are unicellular fungi that obtain their energy by metabolizing organic materials. The most commonly used yeast for baking is Saccharomyces cerevisiae. In this investigation you will determine what types of carbohydrates Baker's yeast prefer.

Materials:

1 packet of yeast or 1 tablespoon

1 ziplock snack or sandwich bag (generic brands best)

100 mls of warm water (~ 70-90° F )

50 mls of crushed Cinnamon Toast Crunch or

50 mls of crushed Fruit Loops or

50 mls of crushed Cheetos or

50 mls of Fruity Pebbles or

50 mls of crushed Smarties

Procedure:

Place ~ 50 mls of crushed cereal, Smarties, or Cheetos into the ziplock bag with one packet or one tablespoon of yeast. Pour ~100 mls of warm water into the bag. Immediately seal the bag making sure all the air is removed. Mix the contents well by gently squeezing the bag. Place the bag on a layer of paper towels and let stand. OBSERVE ! WONDER ! EXPLAIN !

Teacher Tips:

Buy the large bags of generic cereals; they are cheap and as effective as name brands

Keep the packaging so the nutritional information will be available to students

To save time you may want to have the cereals etc. ground ahead of time

Check with the cooks to see if you could get the yeast from or through them. They can buy in bulk.

Work in pairs allowing each group to select their food source.

The kids love this experiment, be prepared for messes when the bags barf.

* Adapted from a lab presented by Science Ed students from the University of Nebraska at the NSTA convention in Kansas City.