Science Buddies: "Ask an Expert"

Hi,
My son is in 7th grade.He has science fair and wants to do a topic related to Probiotics.

His topic is : Do all fermented food qualify as probiotic.He needs some help in this topic.He wants to know how to test for probiotic content in different fermented food and the materials needed.
Or do you suggest us any topic thats related to probiotic - easy to do experiment

We did search google but couldn’t find any information about how to test the fermented food for probiotic content.
It’ll be helpful if you could guide him giving the procedure and the materials required to do the experiment.Thanks in advance!

Hi klyjrs,

This is a very interesting science project idea! To do this, I would recommed buying agar, petri dishes, and swabs from an online website such as homesciencetools. Obtain a sample of the fermented food, and prepare your agar in the dishes. Swab the samples, and spread them on the surface of the agar. If bacteria grows on the surface, it indicates that it habitates bacteria.

There are many detailed instructions for growing bacteria online, if you would like a more detailed procedure.

I hope this helps!
CMS

Hi! I agree that this is a great question, and CMS is absolutely correct in the way to test whether a food contains bacteria. However, just because a food contains bacteria does not necessarily make it probiotic, that is, containing bacteria that will maintain or restore the beneficial bacterial population of the digestive tract. Just about any food (fermented or not) will contain some small amount of bacteria, even if the food hasn't gone bad yet. Most of these bacteria are destroyed in the acidic environment of the stomach, and so they don't qualify as probiotic.

In order to tell whether a food has probiotic properties, you will need a way to test whether the food contains bacteria that survive the stomach's acidity and actually continue to live and grow in the digestive tract. I don't know offhand a simple way to do this, but you could start by searching what types of bacteria typically live in the gut, so that you're identifying species you would already expect to survive such conditions, and then searching what types of foods contain those bacteria. (I know this second part defeats the purpose of an experiment a bit because it helps get at the answer before you've done the test.) Then you might try chemically "digesting" your test foods by placing them in an acidic solution of pH similar to what's in the stomach, and then seeing if that still grows bacteria in a dish like CMS suggested. That's obviously a bit involved, and I'm not even certain that would work, but I think that in order to test for probiotic properties, you need some way to measure the food's bacteria's ability to withstand exposure to acid.

Sorry if I've told you things you may have already learned since taking on this project, and that it was kind of an involved answer! I hope that clarifies things a little bit, and good luck!