How to test germs on store-bought apples?

[ShadowStealerX7]

I am trying to decide on a science fair topic, and I want to do something interesting. I was thinking about testing apples bought from popular local stores to see which were the cleanest. What is something affordable that I can purchase to help test the germs on the apples? Could something like the Glo Germ Premium Mini Kit work?

[grace7177]

Hi- Welcome to Science Buddies!

After researching more on the Glo Germ gel and powder, I found that you can use Glo Germ™ to test germs on different types of fruit. For your experiment, you certainly can use apples. If you want to test something different, I might suggest pears, mangos, or affordable vegetables.

Once you cut up a piece of fruit of your choice, you can use the simulated Glo Germ powder.
According to http://www.hometrainingtools.com/glo-ge ... ts/a/1431/, you rub a small amount of Glo Germ powder on the surface of the fruit. Don't forget to wash your hands before slicing the fruit on the cutting board (be careful!)

Then, using the backlight, you can observe the cross-contamination of germs on the fruit. Try observing around the cutting board, knife, and fruit for signs of germ spots.

This is a great project to see possible consequences of food poisoning resulting from bacterial spread on fruit.
I would also suggest you to find ways in which germs and disease can be limited.

Good luck!
-Grace

[ShadowStealerX7]

Thank you so much!
I came up with this topic on my own and I wanted to make sure it was possible, so can I still use: "Which store sells the cleanest apples?" as my official question?

[donnahardy2]

Hi ShadowStealer,

This sounds like a really great project, and it is original. And Grace has given you some really good advice for your project. The Glo Germ product helps demonstrate how germs are transmitted from one location to another. The product itself is a fluorescent dye that is detected with a UV lamp, but it does not measure microorganisms directly.

To answer your proposed project question, you would have to culture the bacteria and grow them on an agar plate to count them. You would need access to a microbiology laboratory to do this experiment. Here is information on the techniques used to grow and count microorganisms:

http://www.sciencebuddies.org/science-f ... ques.shtml

If you changed your project question to something like, “how do germs spread?” then it would match the Glo Germ project idea. The only problem I can see with this project is that it would difficult to measure the results. You might have to devise a scale from one to 10, or take a photograph of the results. It would be challenging to measure the lumens of light emitted from each sample.

So, you do need to change either the project question or the experiment, but either way, I think it will be very successful. Please post again if you have any questions.


Donna Hardy

[ShadowStealerX7]

Could you go more into detail about how to "grow" the bacteria? Thanks for the info so far.

[donnahardy2]

Hi Shadow Stealer,

Here are the details you need for doing a project involving growing bacteria:

To count the bacteria on the surface of apples, you would need to immerse the apples in a container of sterile water to transfer the bacteria to the water. You would then transfer dilutions of the water to agar plates and incubate the plates for a day or two to allow the bacteria to grow. You would then count the number of colony forming units to measure the number of bacteria in the water. You could report results are number of bacteria per gram of apples. Here is a website that includes a description of this technique and you can search for "standard plate count" or "how to count bacteria" to find more information on the general topic.

http://www.biotech.univ.gda.pl/odl/doc/numbers.pdf

Here is information from the Science Buddies website on microbiological techniques that you would use to grown bacteria.

http://www.sciencebuddies.org/science-f ... ques.shtml

Here is a project idea that includes a detailed list of items and a procedure that you could adapt for this project and information on kits for ordering supplies.

http://www.sciencebuddies.org/science-f ... #materials

And, finally, here are the rules for doing a science project that involves growing potentially hazardous microorganisms.

http://www.sciencebuddies.org/science-f ... ents.shtml

You also need to consider your time deadline. If your project is due on January 15, you might not have enough time to complete this unless you can obtain all of the materials within the next week. Science projects are always better if results are repeated at least two times, and you barely have time to do this one once. It might be better to do the Glo Germ project this year, and save this one for next year.

Please post again if you have any questions.

Donna Hardy

[ShadowStealerX7]

Alright, even if I were to go with how do germs spread, do you still think I wouldn't have enough time?
Do you think the new project question "How do germs on store-bought apple spread from surface to surface" is a good question?
Do you think the answer to the question is too simplistic for a project?

[donnahardy2]

Hi,

Yes, I think you would have enough time to if you did the Glo Germ project. You would have to order the materials and plan the experiment, but the experiment would only take a day or two. And you would have enough time to do a really good job on the project board.

Donna

[ShadowStealerX7]

Do you have any suggestions on how I would categorize my experiment results into a graph? The best I could think of was counting the isolated particles and the dust clusters as one per each surface, and the put all the surfaces and the number of spots of each into a bar graph. Would this be effective? If not, what else do you suggest?

[donnahardy2]

Hi ShadowStealerX7,

It's nice to hear from you again. It sounds like you have gotten some results. Your question is a good one because the results section is very important, and should be the centerpiece of your display board.

You should put your independent variable x-axis and the dependent variable on the y-axis. However, I'm not certain exactly what you did and I don't know what your independent variable was. Please answer the following questions quickly, and I'll tell you exactly what to do:

Is your research question still how do germs spread on apples? When you did your experiment, what did you do? Did you do a controlled experiment and add the glogerm to one apple and then compare different conditions for tracing the glo germ? Please tell me what you did and what your results were.

Here is the information on this website for doing graphs.

http://www.sciencebuddies.org/science-f ... ysis.shtml

Here is the information for making a display board:

http://www.sciencebuddies.org/science-f ... oard.shtml

Donna Hardy

[ShadowStealerX7]

My project demonstrates how germs spread from surface to surface using Glo Germ Powder.
Hypothesis: If I were to cut an apple in half on a cutting surface, and place the halves inside a food container (red side down), the germs from the apple will spread to the surfaces (knife, fingers, cutting surface, and the food container).
Experiment: I washed my hands then lightly covered the apple in Glo Germ, just enough to were you can see only a small amount of the dust, but the apple still looked mostly normal. I then cut the apple in half with a kitchen knife, letting the halves fall on my cutting surface (I used a plastic plate). I turned the lights off and examined the apple, my fingers, the knife, and the plate. I took photographs comparing what they looked like normally (lights on) then under the UV light (the photos were perfect!). Then, I placed the halves into the food container with the inside core facing up. This was to demonstrate how germs from the apple were to spread to the container, as if you were going to take the apples to school or work. I removed the apples from the container and examined the container under the UV light. I actually was surprised to find small particles left in the container.

We weren't assessed on the independent variable, dependent variable, and the experiment type, but from what I did, I would say it was a controlled experiment, my apple was the independent variable, and the surfaces where dependent.

My fingers looked like the had dust on them with the lights on but the dust was completely identifiable under the UV light. The apples looked normal but under the UV light, you could see a bunch of the Glo Germ all over it on both halves. There were also individual Glo Germ particles on the inside of the apple. The plate I used, there were spots around the plate, but in the middle you could see a Glo Germ print from where the apple sat before I cut it, the knife didn't have anything on the right side, the edge of the blade had a cluster in the middle, and the left side had some particles. After I removed the apples from the food container, there were small individual particles and a cluster of dust on the left side. I'm still thinking of where I should tie this in with the food poisoning. I was thinking I would just have in the conclusion section maybe some of the research and an explanation of how food poisoning can occur from cross-contamination, or maybe I should just present it orally.

http://www.mediafire.com/?3jx1ulbgxq8gjqq This is the download link to a zip file with my science pictures in the it. I had to delete 3 of them to meet the mediafire size limit. The pictures were shot in 8 Megapixels so they're quite big.

[donnahardy2]

Hi ShadowStealerX7,

Thanks for sending the link for the pictures; unfortunately I have not been able to open them yet. I will continue working on that, but I wanted to send you a reply because your project is due right away.

The experiment that you did was more of a demonstration type experiment rather than a controlled experiment. You showed that germs on the outside of the apple can be transferred from the apple peel to the inside and to other surfaces by cutting the apple.

For your graph, perhaps you could estimate the percentage of the glogerm that was transferred to the inside of the apple, to your fingers, knife and food container. This could be displayed in a pie chart.

What are your teacher’s requirements for your project? If you were required to do a controlled experiment, you would have had to compare at least two different conditions, for example cutting an apple before and after washing it under controlled conditions. However, you did a great job of demonstrating the concept of germ transmission.

I hope this helps.

Donna Hardy

[ShadowStealerX7]

I want to dearly thank both you and Grace for helping me out with this project. In the end I came up with my own visual aid to be substituted for my graph, a sort of "linking graph" that shows the surfaces the apple traveled to through contact. My project was chosen as one of the top 6 best out of 30 in the school, and then after judging, I won second place out of the entire school. I will be moving on to the Regionals. I am so happy and appreciative, and as a token of my appreciation, I have included both you and Grace in the acknowledgements section of my science log book. Thanks again!

[donnahardy2]

Hi ShadowStealerX7,

Congratulations! Thanks so much for letting us know about the success of this project. And, thanks for acknowledging Science Buddies; we are always happy to help with science projects.

Good luck at the regionals.

Donna