BIOL 170 Exploring Biology

Bread Mold Investigation

The Second Experiment

Background:

Most bread made commercially contains chemical preservatives whose purpose is to extend the “shelf life” of the loaf by preventing the formation of mold for an extended period of time. Home made bread and specialty breads often do not contain preservatives. In this investigation we will compare the effectiveness of preservatives in bread to retard mold growth with bread that does not contain such preservatives.

The introductory bread mold experiments showed the following general results:

Some of the students found that their preservative bread had mold on several days after the onset of mold on their non-preservative bread. By the end of the experiment very little mold was present on the preservative bread with a much greater amount on the non-preservative bread. Other students found mold for the first time on the preservative bread (from the same loaf) on the same day or the following day as the non-preservative bread and while less mold formed by the end of the experiment, the amount was a significant percentage of that measured on the non-preservative bread.

These different results raised at least the following questions:

  1. Under what conditions did each of the students raise their mold? To what extent did these different conditions significantly contribute to the different results?
  2. Both pieces of bread were housed in the same chamber. To what extent didany cross contamination contribute to the different results?
  3. Perhaps you and your partners have other questions about factors that contributed to the different results that need to be examined.
  4. Can you come up with other questions?

Procedure for this second experiment:

1. Form a research group of 1, 2, or 3 people.

2. Determine your research question and null hypothesis statement.

3. Re-design the original procedure (see the bread mold introductory experiment). This new procedure should be developed to study your research question and examine your null hypothesis. The procedure should fit the number of people in your group.

4. Submit for instructor approval before you begin your experiment:

  1. Research question and basis (from the first experiments results) for the question.
  2. Null hypothesis
  3. New procedure

Once you get the final approval from your instructor, your group may begin.

Prepare an experimental report write up using the criteria already specified.