Science Buddies: "Ask an Expert"

Dear Expert/s

My daughter would like to use a scientific fact in her Hypothesis. Her Project question is "Which cheese grows Mold the Fastest". Where/How can we look for a fact that could represnt a Hypothesis for this project.

Thank you .

You have selected an interesting project for a science fair.

A fact is not an essential part of the hypothesis. The hypothesis is usually based on observations made over a number of occasions. As an example, have you noticed one type of cheese in the refrigerator that has more mold or molds quicker than another type. A hpothesis could be somethong like -"yellow cheeses become moldy faser than cottage cheese. You then design an experiment to test the hypothesis. Select a group of yellow cheeses and a cottage cheese. Place a slice of each yellow cheese and a scoop of cottage cheese in a shallow plastic tray or box. Set up at sleast three trays or boxes for replication. Allow the trays to incubate at room temperature on a counter. Observe the experiment each day and record the amount of mold growth (colony size in millimeters) on each cheese. A daily photograph would also document the results. At the conclusion of the experiment the data can be summarized in tables for a report. You can chart average daily growth of the colonies and determine which cheese supports the most/least growth.

If you have further questions please ask.
Matthew W. Mulanax

matthew has given you some great advice. I would like to add that we have a page about the hypothesis: https://www.sciencebuddies.org/science- ... esis.shtml

That page is found in the Project Guide on the science buddies website, which walks you step by step through doing a science project: https://www.sciencebuddies.org/science- ... ndex.shtml

Good luck and let us know if you have any more questions!

Dear Ms Hess and Mr Mulanax

Thank you very much for your replies.

In our preparation for the subject project, we noticed that soft cheese grows mold faster than the hard cheese. Could our Hypothesis read as follows: " The Softer Cheese Grows Mold the Fastest"??

Also, considering experiments, we are planning to run the experiments more than one time, the first run will be in the room temperature while the second one should be in plastic sealable bags placed also in room temperature . The controlled variable would be the cheese types/sizes, the dependent variable will be the growing Mold while the independent variable would be the different testing methods( exposed cheese in room temperature and Cheese in bags in room temperature)
We are planning to use a ruler to measure the Mold growth or maybe we can pre-measure the cheese pieces and estimate the Mold growth in accordance with the set pre-measured units. We will be creating an excel sheet to record the data collected from observations of 2 experiments and the final data outcome will be a graph .

What do you think of the above? any further recommendations/suggestions? I wonder if you could propose a third method of experimenting the Hypothesis above.

Thank you one more time and we appreciate your support and assistance

Regards

Hi Athienah,

Your variables look good, except that only sometimes will the different types of cheese be a control (for example you'd have cheddar cheese in a plastic bag and cheddar cheese uncovered). Across plastic bag/uncovered, the type is a control. But across the whole experiment, the different cheeses are also an independent variable.

So you are testing two different things, the kind of cheese and plastic bags vs. uncovered?

So for every kind of cheese you test, you'll have one that is in a plastic bag and one that is not?

Keep in mind that you'll want to have multiple trials to get enough data, which means you'll probably need to have at least 2 of each when you do the experiment. So if you were testing cheddar cheese, you'd have 2 cheddar cheeses that were in a plastic bag, and 2 uncovered (all of which would be the same size and be exposed to the same conditions).

You'll also need some way of measuring soft vs. hard. You could either make your own scale with defined characteristics, or you could make something that measures how hard something is. Check out this project for an idea: https://www.sciencebuddies.org/mentorin ... p009.shtml

As for another variable to test, maybe you could try cheeses with preservatives? (Like Kraft American Cheese perhaps?)

I hope I answered your questions. Good luck and let me know if you need anymore help!

Dear Ms Hess

Thank you very much for your reply .

When I thought about your reply, I flet that we need to change the Hypothesis or the porject question and the variable to be tested.

I agree that the cheese it self should be the testing variable , meaning in the first run we use different kinds of cheese without preservatives and the 2rd run we use differnt kinds of cheese with preservatrives. Now the question is how can we tell which do and which do not have preservatives, can you please list some names/brands of both types?

Also, we are not so sure what would be a good 3rd testing as we need 3 runs .. maybe if there is a way to measure/determine the moisture level in cheese that could be a good 3rd run, what do you think? if you agree would you please recommend certain names/types ... But, if you do not agree than I would appreciate if you could suggest something else to measured on the 3rd run

We would like to extend our deepest thank for your assistance on this project . It is becoming very enjoyable as much as it is being educational , and the best part is that we are getting the help that would allow us do it in the best scientific way we could

Thanks and respects

Athienah

Athienah,

I want to make sure we are on the same page. Sorry if the following information is obvious to you, I just want to make sure I understand what you are thinking.

Most of the time in science, "runs" or "trials" means the same experiment is repeated multiple times. So 3 runs or 3 trials just means the same experiment was repeated 3 times, with the same control variables and independent variable being tested.

So when I say to do at least 3 "runs" or "trials" I just mean that you should repeat the experiment 3 times to ensure that you have more accurate results and more data to analyze. The more trials you do the better your results will be. At least 3 trials is generally a good rule, but it depends on the experiment. (Experiments that involve giving a survey to people normally involve way more than 3 of them, for example).

Right now we have talked about 3 independent variables: (1) the softness of cheese, (2) the degree of covering (uncovered vs. covered), and (3) preservatives (presence or lack of).

You don't need to test multiple independent variables unless you want to. This depends on how much time your daughter has to complete the experiment, as well as how much work she wants to do on the project.

You could just pick one of these independent variables to test, or you could do all three.


So, let's just pretend your daughter sticks with the softness of the cheese. Let's say she has 3 cheeses with varying degrees of "softness." I'll just call these cheeses "soft, medium, and hard"

So, in order to do this experiment 3 times (3 trials) for the degree of softness independent variable, you'd need 3 pieces of each type of cheese, so 9 total. In this type of experiment, you could actually test all 9 pieces of cheese at once, which makes it easier than other projects.

If you decide to do another experiment, let's say testing the degree of covering, in this case you would actually need 6 pieces of each kind of cheese, so 18 total. You'd need 3 pieces to be covered and 3 pieces to be uncovered for each type of cheese.

So if you did both these experiments, you would need 27 pieces of cheese (9 of each type).

With preservatives, you would just add a couple of cheeses with preservatives to each of these two experiments (so you'd maybe have 5 different types of cheese, 3 regular "natural" cheeses and 2 artificial ones, for example). Then after each experiment is done, you could look at the results and see if overall (across both experiments), whether the cheeses with preservatives grew mold less quickly than the "natural" cheeses. In a way, you'd actually be testing two independent variables at the same time. Normally this is discouraged (if you change more than one thing at a time, you won't know which variable caused the outcome), but this experiment is unique in that each cheese is separate. Really, each piece of cheese is its own experiment .

Does this make sense?

As for cheeses with preservatives, Kraft Singles and Velveeta might be good.

Hello Ms Hess

Thank you for your reply.

We are currently working on designing the experiment and we shall come back to you on our final designed plan. We really would like to ask you for a professional opinion before we submit it to the teacher

Thanks

Hello again Ms Hess

We have a real quick question which we could not find a definite answer to . Does Mold have Odor/Taste?

We are talking about Mold in general not only the cheese Mold..

We klnow that the indoor Mold smells and some of the food Mold does as well (specially fruits, meat and vegetables) Correct????

Any way we would like to hear your valued opion on the above question, specific details on Cheese are highly apprecited

Thank and best regards

Athienah

Hi,

I don't know too much about the different kinds of mold (or much about cheese for that matter), but I would think that mold would have a taste because it secretes enzymes to break down food. Plus, it probably has a taste because it is organic matter. Molds are fungi and so are mushrooms, so I think they would have a taste. (Obviously most molds are not safe to eat! Only some cheeses have safe mold...in fact, cheese is often created from edible kinds of mold ).

I found this on the wikipedia page about mold:
"Typically, molds secrete hydrolytic enzymes, mainly from the hyphal tips. These enzymes degrade complex biopolymers such as starch, cellulose and lignin into simpler substances which can be absorbed by the hyphae. In this way, molds play a major role in causing decomposition of organic material, enabling the recycling of nutrients throughout ecosystems. Many molds also secrete mycotoxins which, together with hydrolytic enzymes, inhibit the growth of competing microorganisms."

The mold releases chemicals to break down the food, so you would smell these chemicals and the decomposition of the food.

I found a page about blue cheese and how it is made from mold: http://cheese.about.com/od/howcheeseism ... cheese.htm
I would also take a look at this wikipedia page about cheese: http://en.wikipedia.org/wiki/Cheese

It goes into some details about how cheese is made. After reading those, if you have more questions let us know!

Dear Expert,

My daughter is writing her Material list and her procedure now which made us think of the following question:

Do we have to inoculate the cheese samples with Bacteria in initiate the mold growth, or we can just put each sample in a zip lock bag and store all of the samples in one place and wait for them to start growing the mold??? I know in the second case it would take longer time to grow the mold but certainly it would grow it ...

Appreciate your earliest reply as she will have to submit her paper tomorrow

Thanks for your usual cooperation

Regards

Your idea of placing the cheese in plastic bags and using naturally occuring mold is a good one. You can assume that all the cheese is exposed to the same level of naturally occurring inoculum in the ambient environment (kitchen or work room) when the experiment is set up. An easy to measure the mold development is to estimate the percent of the surface of each piece over time. I would be a good idea to make each piece of cheese about the same size and make the estimates every day.

Good luck,

Matthew Mulanax