bread experiment variables

MOLD GROWTH ON BREAD AND FRUIT

LEARNING OBJECTIVES

Differentiate between fungi and bacteria.

Perform basic mycological culturing.

Identify common household molds based on their macroscopic characteristics.

MCCCD OFFICIAL COURSE COMPETENCIES

Identify structural characteristics of the major groups of microorganism.

Compare and contrast prokaryotic cell and eukaryotic cells.

Compare and contrast the physiology and biochemistry of the various groups of microorganisms.

Apply various laboratory techniques to identify types of microorganisms.

Utilize aseptic technique for safe handling of microorganisms.

You want to grow mold, so you need bread that does not contain preservatives (natural or artificial), Please go the bakery section of the grocery store and look at the ingredients of bread they baked. Find bread that does not contain ascorbic, citric acid, or lactic acid and purchase that. Bread from the bread aisle will contain artificial or natural preservatives and therefore cannot be used in this experiment.

PHOTO REQUIREMENTS

Take a photo with your photo ID during the lab exercises when you see this icon.

Paste these photos into the Mold Growth on Bread and Fruit Questions Document.

introduction

Mycology is the study of fungus. Fungi can grow in a wide diversity of environments, but most species require moisture. Fungi grow slower than bacteria, at a lower temperature, and lower pH than most bacteria prefer. Most fungi are unable to ingest food and must absorb nutrients from their surrounding environment. For this reason, fungi must grow directly on or in their nutrient source. Fungi secrete enzymes into their surroundings to help break down their food source and facilitate the absorption process. Fungi are eukaryotic organisms which grow as either unicellular yeast or multicellular mold.

Mold plays an important role in the environment by breaking down and digesting dead organic material. Mold reproduces asexually by producing microscopic spores, similar to seeds produced by plants. Mold spores are ubiquitous; they are found everywhere both indoors and outdoors. Mold spores can easily float through the air and can be carried great distances. The number of mold spores suspended in indoor and outdoor air fluctuates from season to season, day to day, even hour to hour. If mold spores land in a suitable growth environment, they will germinate to produce new mold.

Mold produce multicellular filaments called hyphae.  Hyphal filaments intertwined into a mass, known as mycelia, can be seen macroscopically as fuzzy or hairy colorful growth. Mold absorb food through their extensive network of mycelia. There are three common household molds Rhizopus (white), Aspergillus (black) and Penicillium (green) you are likely to grow. In this experiment, you will determine which factors encourage mold growth on pieces of bread and apples.

Read all instructions carefully before you start the experiment.

EXPERIMENT VIDEO GUIDE

1. Use the measuring cup to measure and add 1/4 cup or 4 ounces of water to a saucepan or microwavable bowl and mix in 1/2 cup of sugar.

2. Gently heat the water-sugar mixture on the stove or in the microwave, stirring occasionally until all of the sugar is dissolved. Use caution when removing the solution from the microwave/stove as it will be hot. Allow the solution to cool. The cooled sugar-water solution will be a little thick, like syrup.

3. Use the permanent marker or grease pencil to label the plastic bags with the following titles: “Bright, Control,” “Bright, Water,” “Bright, Sugar,” “Bright, Lemon or Lime,” “Dark, Control,” “Dark, Water,” “Dark, Sugar,” and “Dark, Lemon or Lime”.

4. Cut the 6 slices of bread into 24 pieces total (4 pieces from each slice).

5. Cut the apple into 24 slices.

6. Place 3 pieces of bread and 3 slices of apple into each plastic bag.

7. Add 1 teaspoon water to the two bags labeled  “Bright, Water” and “Dark, Water”; add 1 teaspoon of the cooled sugar-water solution to the two bags labeled “Bright, Sugar” and “Dark, Sugar”; add 1 teaspoon of lemon or lime juice to the two bags labeled “Bright, Lemon or Lime” and “Dark, Lemon or Lime”. Do not add anything to the bags two labeled Control.

9. Find a well-lit, warm location (e.g. a windowsill or under a lamp) in which to place the 4 bags labeled “Bright”.

10. Find a dark, warm location (e.g. a warm closet) in which to place the 4 bags labeled “Dark”.

11. Examine the bags every day for 14 days and look for mold formation on the bread and apple pieces. Record the day (1-14) that mold growth was observed in the data table in the Mold Growth on Bread and Fruit Questions document. If no mold growth was observed in 14 days, record “no growth”. For example, if mold was first observed on the bread in the “Dark, Water” bag on day 3, record 3 in the data table. If no mold growth was observed in the “Control, Dark” bag after observing the bag every day for 14 days, record “no growth” in the data table. On day 14 record the number of pieces of apple (0-3) and the number of pieces of bread (0-3) in each bag that have mold growth in the data table.

AFTER 14 DAY INCUBATION WITH DAILY DATA COLLECTION

2. Do not open the bags when you are finished with the experiment. This will disperse mold spores and contaminate your work area. Dispose of the sealed bags in the trash and remove the trash bag from your living area.

DISCOVERIES IN MICROBIOLOGY

In 1950, American chemists Elizabeth Hazen and Fuller Brown discovered the antifungal drug nystatin. Hazen (in New York City) cultured hundreds of soil samples from around the world and tested them in vitro for activity against two fungi ( Candida albicans  and  Cryptococcus neoformans) . If the culture killed the two test fungi, she would mail the culture in a mason jar to Brown (in Albany New York).  Brown isolated the active agent in the culture and would send it back to Hazen. Hazen would then test it again against the two test fungi. If the active agent from the culture killed the two test fungi, its toxicity was evaluated in animals. Nearly all the agents that killed the test fungi turned out to be highly toxic in animals. Hazen and Brown tested hundreds of soil samples from around the world. The one successful culture was found in soil from the garden of a friend of Hazen. The culture contained an active agent they named nystatin (for New York State).  Nystatin has been used for years as an effective treatment for fungal infections of the skin, mouth, vagina, and intestinal tract.

Hands On Microbiology Copyright © 2022 by Jill Raymond. All Rights Reserved.

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Mold Bread Experiment

What makes mold grow.

We are going to perform a mold bread experiment to grow our own mold and find out whether mold does indeed grow faster at higher temperatures.

This article is a part of the guide:

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• 2 How to Conduct Science Experiments
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• 5.5 Make Heron’s Fountain
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In ten days you will be able to answer this important question and make a contribution to science!

But what is mold? What makes it grow?

What is Mold?

Mold is something that we often take for granted, as something that makes us have to throw the bread away or the cheese smell bad.

Mold is, in fact, a fascinating organism which has had many different uses over the years and our lives would not be the same without it.

Most of us know that food seems to become moldy more quickly in the summer than in the winter when it is colder. Food in refrigerators seems to keep longer than food left out in the sun. Is this true? Does temperature really affect the rate at which mold grows?

Important Note

Please note that some people are allergic to mold; ask your doctor or parents. If this is the case, do not pick the Mold Bread Experiment. Always wear gloves and a mask, wash your hands, and don’t eat or drink whilst you are performing this study.

Performing the Mold Bread Experiment

In the Mold Bread Experiment we are trying to prove that;

"Mold grows quicker at higher temperatures."( Hypothesis )

What You Need for the Mold Bread Experiment

• 15 slices of bread. Any sort will do but it is perfectly fine to use cheap white sliced bread as then you will know that all of the slices are a similar size, weight and thickness. You must make a note of the brand and use-by date so that anybody else wanting to repeat the Mold Bread Experiment can use the same type.
• 15 sealable sandwich bags
• 1 piece of film or clear plastic with a 10x10cm grid drawn onto it
• Clean knife
• Chopping board
• Sticky labels
• Mold Spores - if you can’t get these from your school don’t worry. There are mold spores all around us in the air which will eventually grow on the bread but your experiment will take longer.
• Using the sticky labels and the marker pen label the bags. Mark 5 bags as ‘A’, 5 as ‘B’ and 5 as ‘C’. You also need to label each set of bags 1 to 5.
• Cut the bread into 10 x 10 squares using the chopping board and knife.
• Inoculate the bread thoroughly with the mold solution. Try to coat each slice with a similar amount of the culture although this can be difficult.
• Put one slice of this bread into each bag and seal the bags tightly.
• Put the 5 ‘A’ bags into the freezer, the 5 ‘B’ bags into the refrigerator and the 5 ‘C’ bags somewhere safe in a warm room. Because the bags in the freezer and fridge will not be getting much light it is best to cover the ‘C’ bags to make sure that light is a constant.
• Every 24 hours, preferably at exactly the same time every day, using the plastic grid, count the number of square centimeters of mold on each slice of bread. If the mold covers more than half a square, count it as 1cm, if less than half a square, count as 0 cm. You must never open the bags.
• You should repeat these counting processes for 10 days or until there are significant measurable results .
• Keep a careful note of your results for each slice of bread for the entire duration of the experiment. You can even take pictures or draw the slices if you want to be really scientific!
• Average the results for sample types A, B and C.
• Once you have finished, throw out all of the bags without opening them.

Because each square of bread is 100 cm2, you can express your results as a percentage. For each of the bread types, A, B or C average the amount of mold grown over the ten days and write these figures into a table.

You can then plot this information onto a graph and begin to explore your results. You can plot the amount of mold on each bread sample and compare it to the number of days, like in the diagram below. This can be done with a sheet of graph paper and colored pens or on a computer.

Is the Graph Correct?

Could you replicate the graph below or is your graph different? We have done this, but will not give you our answer, so you can test for yourself!

Why are the Results Important?

The food industry spends millions of dollars every year on refrigeration and it is very important that they know what temperature they need to stop mold from growing. Moldy food must be thrown away and this costs restaurants and manufacturers a lot of money.

For companies using mold to make food or medicine they need to know at which temperature mold grows best. The faster the mold grows, the quicker they can sell their product and make money.

Further Experiments

Now that you have finished and obtained some results, maybe you want to see if other variables affect the rate at which mold grows. Maybe you could keep the temperature the same for all of the samples but use different types of bread.

You could try adding moisture to the slices or putting different amounts of sugar or lemon juice onto the slices. As long as you only vary one thing at a time, you can make some interesting studies about mold.

Temperature is not the only thing that affects the rate of mold growth so feel free to try and find out more about this interesting organism.

Facts About Mold

• Mold is not a plant but a fungus like mushrooms and toadstools. It grows on food and other organic matter, breaking it down into slime and extracting nutrients for growth.
• Alexander Fleming discovered that a common type of mold fungi kills germs. From this, he made a medicine called penicillin which has saved millions of lives over the last 80 years. Many other life-saving drugs are made from chemicals obtained from mold.
• Mold is one of nature’s cleaners. It breaks down dead organic material and recycles the nutrients back into the soil. It is essential in nearly every ecosystem in the world.
• We use molds for flavor in some foods such as blue cheese, soy sauce and Quorn (TM) .
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Martyn Shuttleworth (Nov 24, 2008). Mold Bread Experiment. Retrieved Nov 13, 2024 from Explorable.com: https://explorable.com/mold-bread-experiment

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