Effects of Food Preservatives on the Freshness of Food materials

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Author: Janice VanCleave

In our complex world, food products have to be shipped for long distances and/or stored for periods of time. It would be difficult to transport and store most kinds of food without using preservative additives.

In this project, you will have the opportunity to test the effectiveness of calcium propionate, a food additive that inhibits mold growth in bread. The effect of this additive in different types of bread as well as the effect of temperature on the preservative will be determined. You will also analyze other methods of preserving food.

Getting Started

Purpose: To determine how effective the food additive calcium propionate is in inhibiting the molding of bread.


  • paper towels
  • water
  • 6 plastic 1-gallon (4-liter) size zip-lock bags
  • 6 slices of white bread with propionate
  • 6 slices of white bread without propionate or any other preservatives
  • marking pen
  • masking tape
  • magnifying lens (handheld type)


  1. Moisten one paper towel with water and lay it inside one plastic bag.
  2. Place one slice of bread with propionate and one without side by side on top of the moistened paper towel inside the bag.
  3. Zip the plastic bag closed.
  4. Use the marking pen and masking tape to label the bread with and without propionate. Place the label on the outside of the bag above the indicated slice of bread.
  5. Repeat the procedure (steps 1 through 4) preparing five additional bags with two slices of bread, one slice of bread with propionate and one without, inside each bag. Note: Six bags is not a significant number, but it does provide enough samples to verify your results.
  6. Keep the six bags of bread at room temperature.
  7. Examine the slices each day with the magnifying lens.
  8. Continue observing the bread for two weeks or until every slice has become moldy. Record the length of time required for each slice to mold.


Given enough time, all of the bread slices become moldy. However, the slices with calcium propionate mold more slowly. (see Figure 20.1)


Calcium propionate is a food additive on the U.S. Food and Drug Administration's GRAS ("Generally Recognized As Safe") list. At low concentrations, it is considered harmless to humans but inhibits the reproduction and growth of mold. The addition of calcium propionate to bread allows the product to be stored for longer periods of time.

Microbes are fussy about their diet, and different species can be found on specific foods. Food preservatives are chemicals added to food to prevent spoilage. Calcium propionate is a preferred preservative for bread because it retards the rapid growth of bread mold, increases the content of calcium, and avoids the possibility of decreasing gas formation during baking.

Try New Approaches

  1. How effective is calcium propionate in breads other than white bread? Repeat the experiment using different breads, such as wheat, rye, potato, and raisin. Science Fair Hint: Record results of the original as well as this experiment and display the data tables.
  2. Does temperature affect the effectiveness of the preservative calcium propionate? Repeat the original experiment using two sets of bread samples. Place one set in the refrigerator and place the second set in a warm area such as on top of a refrigerator. Science Fair Hint: Take photographs as each experiment progresses to show the changes in the food as a result of containing or not containing calcium propionate.

Food Preservatives

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