Biology Urgent: How do I measure the rate of growth of mould/yeast on certain types of bread.?

Question

I will be using Rye, Wonder Bread White, Wonder Bread Whole Wheat, Pumpernickel, and maybe another type of bread. I will get four slices from each Loaf/Package to make sure results aren't skewed, I will put them each in a resealable bag, in a controlled enviroment, no direct heat or freezing. It will occur over 15 Days. Each day I will be observing changes in the bread. The bread expirey dates will be approximately the same.

Now my question is how do a measure the rate of mould/yeast growth.

This is a LAB for my end of term in grade 11BIO

Answer 1

a grid (in cm squared) onto a piece of acetate an place it over the bread but careful not to spread the mould from one type of bread to another

measure the area covered by mould by counting the squares and average it ... do the same for all types of bread.

Hope this helps
x
good luck

Answer 2

Yes, you could could grid squares, but it would be easier to do an approximation. On a consistent surface, mold tends to grow in circular colonies. This means that you can measure the diameter and use the equation for the surface area of a circle to estimate the surface area covered by the mold. If a colony becomes a bit non-circular, try averaging the short and long diameters and throwing that into the equation.

circle area = pi * radius * radius, or pi*r^2

Two problems to avoid:

- Bread with a lot of preservatives, like Wonder Bread, will not grow mold too quickly.
- Each slice will have different amounts of mold spores in the beginning due to packaging, conditions at the bakery, conditions in the air at your place, and conditions during shipping and storing of the loaf. If the different types of bread start off with very different amounts of mold spores, the results are going to be skewed.
I suggest first creating one slice of very moldy bread. Then put the same amount of mold (a crumb size) onto the center of each test slice and only measure the mold growth around that innoculation site. Obviously, the crumb-size innoculation isn't going to be very precise, but it's better than relying on the unknown.

Answer 3

Mold will eventually grow on the stale bread as long as you keep it in the bag so that it doesn't completely dry out like a crouton. It grows better in moist conditions.

Answer 4

Calculate the area covered by the fungus, better yet, the areas covered by the different species of fungus. Something transparent with grid lines could be useful. Plot it over time.