How the Type and Wavelength of Light Affects the Amount of Mold Growth on

White Bread

By: Ben Griffiths, Kenny Aronson, and Mark Walker

IntroductionRationale to see what environmental variables affect mold growth

Needs spores to be on foodGrows on food source

Purpose to find out which type / color of light affects mold growthHypothesis: no light will yield the most mold

Light WavelengthsAtoms release energy and photonsDifferent wavelengths of lightOnly some can be seenUV is higher wavelengthX-rays are a few millionths of a mmUV has more energy

Can cause molecules to break apartKilling mold etc

Black light (UV) White light Blue light Red light No light

1 trail 1 trail 1 trail 1 trail 1 trail

Experimental Design

IV: the type of light, i.e., Black, white, blue, red, and no light

DV: the amount of mold that grows on the bread

Constants:•The types of light (black,white, blue, red, none)

•The time exposed to light (constant exposure, lights never off)

•Amount of water put on bread per application (dependant on day)

•The type of bread (white bread)

•Amount of bread (full petri dish)

•Temperature and humidity of room (room defined)

•Where samples were placed (similar cabinets)

•The length of the experiment

•Number of trials per type of bread (1)

Procedure1. Obtain all necessary equipment.

• Bread, 5 Petrie Dishes, 3 Lamps, 1 Black Light, 2 Color Filters (red and blue), Graduated Cylinder, Camera

2. Size the bread so that it fits tightly in the Petrie dishes.

3. Take a picture of each dish. This represents the day 0 observation.

4. Cover 2 of the white light lamps with the colored filters so that they are each a different color.

5. Find 5 separate cabinets or dark places in which the dishes can be stored where they will not be destroyed.

6. Put a different bread sample in each place and set up the lamps so there is one with black light, white light, blue light, red light, and one with no light.

7. For the first observation period leave the bread uncovered so that it can collect mold spores.

8. After each period, take a picture of each sample, labeling the day as well.

9. Add appropriate amount of water to each bread sample to remoisten it after every observation. Be sure to keep the amount constant for each sample.

Results

Black light No light

White light

Blue lightRed Light

Day 0

Day 3

Day 5

Day 12

Micro specimensZygomycetes

RhizopusDeuteromycetes

Penicillium 2-5 μm

Blue, Red, No Light White, Red, No Light

Micro specimensDeuteromycetes

Aspergillius 2-5 μm

ZygomycetesMucor

White Light

ConclusionUV Light yielded least moldLight color with same kind of source made no differenceNo light produced about the same amount of moldWould use fluorescent next time