Question about How Do Food Preservatives Affect the Growth of Microorganisms? activity

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AS3002
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Question about How Do Food Preservatives Affect the Growth of Microorganisms? activity

Post by AS3002 »

Hi,
I am planning on doing the experiment of how spices affect the growth of microorganisms by mixing them with rice. I am planning on observing the growth of colonies and which plate give the quickest and the farthest result.

I was wondering for the following experiment to be successful, how do I control the exposure towards bacteria to be equal for all plates.





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SciB
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Re: Question about How Do Food Preservatives Affect the Growth of Microorganisms? activity

Post by SciB »

Hi and welcome to Scibuddies. I will try to help you answer your question so you can perform the experiment successfully.

The key to doing good science is to be careful to treat all the samples exactly the same (except for controls that lack the test ingredient). In this experiment, you said you were testing the effects of adding a spice to rice as a preservative against bacterial growth. No bacteria are added to the test material, so the sources of bacteria would be the rice, the spice, the water you use to cook the rice, any utensils used in the cooking, the containers for holding the samples and the air itself.

So, to ensure that the bacterial exposure is approximately the same in all cases, you should use the same batch of rice for all tests, the same source of water (I recommend sterile distilled water from a fresh jug), the same containers and utensils, and the same area for holding the samples until you spread them on the nutrient agar plates.

It is a good idea to do three samples for each test including the control (no spice) so you can average them and get a more accurate colony count.

Does this answer your question? If you have more questions, just post them and I will be happy to answer them and explain things so you will understand them.

What spice are you planning to use? One of my favorites is turmeric because it is yellow and makes the rice a pretty color--as well as tasting good! :)

Best wishes,
Sybee
AS3002
Posts: 2
Joined: Wed Jan 05, 2022 10:58 pm
Occupation: Student

Re: Question about How Do Food Preservatives Affect the Growth of Microorganisms? activity

Post by AS3002 »

Hi,

Thank you so much for your reply! This has certainly helped me so much!

I also just have one more question. So, to take readings of the area covered by the fungal growth, I thought of printing the graph sheet on transparent paper and counting the squares it covers. Would this be an accurate way of measuring?

haha my favorite is turmeric too! I have chosen turmeric, cinnamon, and cumin. I chose clove too but the fungal growth for clove is not visible. it's very minimal and difficult to count the area covered. do you have any suggestions for the 4th spice I could use?
SciB
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Joined: Fri Feb 01, 2013 7:00 am
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Re: Question about How Do Food Preservatives Affect the Growth of Microorganisms? activity

Post by SciB »

Hi again,

Glad my answers helped you. When i count bacterial and fungal colonies on a plate I like to count all of them, but sometimes that's impossible because there are too many. What I do then is turn the plate over and using a sharpie pen, divide the circle in half and then in half again so there are 1/4 circles. You can count half the plate or 1/4--whichever has a reasonable number of colonies (50-100).

After you spread the liquid on the plates, keep them in a warm place, 25-30C, in the dark. Check after one day and if the bacteria have not grown much then let it go another day.

Also, be sure to take a clear photo of each plate to show in your report. You can also count colonies on the photo.

Hope this helps. Post again!

Sybee
SciB
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Posts: 2066
Joined: Fri Feb 01, 2013 7:00 am
Occupation: Retired molecular biologist, university researcher and teacher
Project Question: I wish to join Scibuddies to be able to help students achieve the best science project possible and to understand the science behind it.
Project Due Date: n/a
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Re: Question about How Do Food Preservatives Affect the Growth of Microorganisms? activity

Post by SciB »

Oh...forgot to suggest spice #4. Garlic is supposed to be antibacterial, so mix some garlic powder in with the rice--that with turmeric and cumin should make it delicious, to us at least--hopefully the bugs won't like it!
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