MadSci Network: Chemistry

Re: Explain the banana and 7-Up soda reaction in the stomach.

Date: Fri Jul 28 18:45:55 2000
Posted By: Kieran Kelly, Consultant, The Boston Consulting Group
Area of science: Chemistry
ID: 964809203.Ch

Well, I can't say I've ever witnessed this reaction but I can well imagine its impact. First - please don't try this experiment out on your friends or enemies. It's not very nice to have to pick chunks of banana out of your nose or to clean up this mess later.

Second - the reaction taking place sounds very similar to an ice cream float, except it occurs in a high temperature, "closed system" with banana proteins instead of milk. The combination of the protein and the carbon dioxide causes foaming and the foam has only one way out of your stomach - the way it came in. Here's how it works:

The banana supplies the protein and the cold soft drink adds a lot of carbon dioxide to your stomach. Your stomach is quite warm - much warmer than the soda - which means the carbon dioxide becomes less soluble at the higher temperature and gas bubbles are making a very fast escape from the liquid. The banana protein coats the CO2 bubbles and makes a very stable, expanding foam in your stomach. The creation of the foam means you can't just burp to get rid of the CO2 in your stomach, but it has to get out somehow because your stomach is only so large... so an escape is made using its only available exit.

So, I am left wondering who thought up this wonderful experiment (again, don't try this one at home). Even though the mechanism is an interesting one, I prefer a rootbeer float to demonstrate the same principles. And it tastes much better! ;)


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