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Food preservatives are chemicals that get added to food to prevent spoilage. And any
way you slice it, foods like bread need preservatives to stay fresh while being shipped over long
distances or put into storage. So how well do food preservatives preserve food? Put them to the
test with this bread mold experiment (it'll really grow on you)!
What you'll need:
- paper towels
- water
- six plastic one-gallon (four-liter) size zip-lock bags
- six slices of white bread with calcium propionate (be sure to read the ingredient label carefully)
- six slices of white bread without calcium propionate or any other preservatives
- marking pen
- masking tape
- hand-held magnifying glass
What to do:
- Moisten a paper towel with water and place it inside one plastic bag.
- Place one slice of bread with propionate and one without propionate side by side on top of the
damp paper towel inside the bag. Then zip the bag closed. (By doing this, you will notice how two
slices of bread representing two variables, will react to the same conditions in the same bag.)
- Using the marking pen and masking tape, label the slices "with propionate" and "without
propionate." Place the label on the outside of the bag right above the appropriate slice of bread
- Repeat steps one through three and prepare five more bags, each with two slices of bread (one
with preservatives, one without) inside each bag.
- Keep the six bags of bread at room temperature. Examine the slices each day with the
magnifying glass.
- Continue observing the bread for two weeks or until each slice has become moldy. Make a note
of the length of time it has taken for each slice to grow mold.
What happens:
All the bread slices become moldy over time. But the slices with calcium propionate
grow mold more slowly.
Why this happens:
Calcium propionate is a preservative that is generally considered safe by the U.S. Food
and Drug Administration. In small doses it's harmless to people. It also slows down the rapid
growth of mold and allows bread to be stored for longer periods of time.
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