LONG-TERM INVESTIGATION Sarah Manternach Haley Tietz Crystal Nuci Kylie Bontrager

Does the amount of preservatives in bread affect the amount of mold growth? Does the presence of light affect mold growth?

Materials  9 Petri dishes  3 slices of organic whole-wheat bread  3 slices of store-bought white bread  3 slices of homemade French bread  9 plastic bags  9 square grids  Place of constant light, place of changing light, place of constant darkness  One brown paper bag

Procedure  We began by cutting the bread into the grid-sized portions that fit inside our Petri dishes. We placed the Petri dishes inside individual plastic bags and labeled them according to their bread type. We put one of each of the kinds of bread into three different lighting settings: constant light, changing light, and constant darkness. We made a table to record our mold growth findings 2 times a week for 3 weeks.  We designed our research based on which type of bread produced the most mold. We also used our findings to determine the types of mold we were seeing in the different light settings.

Findings-Homemade Bread  We reported that mold growth started on day 5 of the investigation.  By day 12, the homemade bread in the constant light had 100% mold coverage  By day 19, the homemade bread in the changing light had 100% coverage.  The homemade bread in the dark did not reach 100% mold coverage in all 3 weeks, but it was around 80% molded.

Findings-Store bought Bread  On day 21, 2 squares of mold appeared on the bread in changing light.  On day 26, 1 square of mold appeared on the bread in the dark.  There was no mold growth present on the store-bought bread in the constant light.

Findings-Organic Bread  There was no evidence of mold growth on any of the three organic bread samples in any of the lighting settings.

 The more preservatives present in the bread, the less mold growth.  Light had an indirect effect on mold growth.  Bread containing yeast is more likely to grow mold.  Store-bought bread, which contains the most preservatives did not show growth until the final days. The growth was minimal. Homemade bread and organic bread do not contain preservatives.  “Light can have an indirect effect in increasing the temperature, therefore increasing the growth of the mold, and drying out the bread, therefore decreasing the growth of mold, since the mold prefers a moist environment.”  The store-bought bread and the homemade bread both contain yeast. However, the store- bought bread contains the preservatives that keep the bread from molding. The homemade bread does not have preservatives to keep the yeast from molding. Claim Evidence

Reflection  We faced a lot of questions during our mold growth investigation. Because we had so many determining factors (moisture, preservatives, presence of yeast, and light), we had a difficult time explaining why mold was present in some situations and not in others.  After looking back on our predictions, we realized the factors we looked at were accurately predicted, but we did not take into consideration other variables such as the presence of yeast and moisture.  Next time we buy bread, we are going to keep it in the freezer because we don’t eat enough sandwiches to eat it before it molds.

References  affect-growth-mold-bread.html affect-growth-mold-bread.html  04/ Ot.r.html 04/ Ot.r.html  recipes/bread-mold-causes.htm recipes/bread-mold-causes.htm