Re: Science fair bread mold

Ben,

This sounds like a very interesting science project, I hope you do well.

1. Calcium Propionate is a preservative. Its main function is to inhibit mold growth, is less effective against bacteria, and has no great effect on yeast. It is used in products with lower pH (a measure of acidity), typically fermented products like bread and cheese. In products with low water activity (a measure of how much water is available for microorganisms to grow) mold will be the way that it spoils. Bacteria and yeast require much more water to grow.

Potassium Bromate, on the other hand, is not a preservative. Bromate is called a dough conditioner. Chemically, it is called an oxidizing agent. In bread it has two main purposes:

• A protein called gluten is needed to trap gas and expand when the dough is proofing. Without good gluten breads would be thin and dense (if your potato or rye breads don't have added gluten they will give you an idea of what I mean). Since consumers like their bread to be airy and light good gluten is needed. Bromate can help a lower quality gluten perform like a good gluten, providing a better looking loaf of bread.
• Another characteristic that consumers like in bread is small, uniform air cells. If you look closely at the bread you will see that there are many small holes in it. Bromate helps the gluten form small, uniform holes in the bread. Without it the holes would be big, the bread more spongy, and butter would melt into the big holes instead of covering your toast evenly.

For a long time it had been thought that all the potassium bromate was destroyed in the dough proofing and baking process. In the 1980's more sensitive chemical tests were developed. These tests are capable of measuring a few part per billion. As an example, the state of Louisiana is about 160 billion square yards in size. One room about 38 feet long on each side (probably about the size of your classroom) would be one part in a billion, where the entire state of Louisiana is the billion.

Although these small amounts have never been shown to cause cancer in people, some countries have banned its use. Some people who are very concerned about their health have chosen to not eat products that use bromate. That is why some companies advertise that their products are bromate free.

3. There are thousands of species of mold. Mold species are identified largely by their morphology, how they look and are put together. It takes someone with a very good knowledge of molds, skillful in the prepartion of slides, and with expertise in the use of microscopes to differentiate species of mold.

Potato slide agar cultures stained with lactophenol blue. Pictures taken at 40X magnification by Lynn Bry, MD/PhD. Dept. Pathology Brigham & Women's Hospital.

Rhizopus mold.	Aspergillus mold. The "peacock" shaped structures are fruiting bodies with spores.

I hope this information is useful to you.