Instructables

Kitchen laboratory II: The CO2 trap

Featured
In this instructable, I'll show you how to make the classic natural indicator from red cabbage and then, will use it to demonstrate the production of CO2 during the fermentation process of the yeast Saccharomyces cerevisae.

This is a very simple and fast demonstration, however I think is a nice one and you can show it to your kids, I'm sure they are going to be impressed and they will learn something about bread making.
 
 
Remove these adsRemove these ads by Signing Up

Step 1: Saccharomyces cerevisae and CO2

First, let me introduce Saccharomyces cerevisae, this yeast is also known as brewers yeast or beakers yeast and I'm sure you can guess its main uses in Food and Beverage Industry. In this instructable I'm going to explain Sacharomyces role in bread making.

Saccharomyces comes from Greek meaning sugar mould and Cerevisiae comes from the Latin meaning of beer.

Bread making is known since ancient times (archeologists have found evidences of bread making in ancient Egypt.) and Saccharomyces cerevisae is responsible for many of the desirable characteristics in bread.

When Saccharomyces is added to the dough, it changes sugars present in the flour or added to the dough, giving off carbon dioxide (CO2) and alcohol (ethanol). The CO2 is trapped as tiny bubbles in the dough and expands the flour's gluten proteins, and as a result, causes the dough to rise, while alcohol is rapidly evaporated during baking. This process is called fermentation and is the way for gaining energy for many microorganisms

So, in bread making, the carbon dioxide is the more important of the two products, with the evolving gas causing the bread dough to rise. On the other hand, in beer and wine-making, the alcohol is the important product, although the carbon dioxide may be used in beer and champagne.

Shacharomyces is not only important for food and beverage production but for genetic investigation.

Because of the importance of this yeast in Industry and the role of CO2 in breadmaking, I think it could be interesting to use it for the Science Fair contest so I designed this simple experiment to demonstrate the production of CO2 during Saccharomyces cerevisae sugar fermentation.

To do this, we are going to make a very simply home apparatus to collect the CO2 produced during fermentation and then, will conduct it into a red cabbage solution which will act as a pH indicator.

We will need a pH indicator to demonstrate the presence of CO2 because when we make CO2 solution in water it forms carbonic acid (H2CO3), so we can detect the formation of this acid using a pH indicator.
ifeyinwa1 year ago
visit our website for educational research works http://www.unn.edu.ng/
lemonie7 years ago
Do you know over what pH range this indicator operates? L
syribia (author)  lemonie7 years ago
It works over a wide range pH
Check this link, there is a red cabbage pH chart from 1 to 12
lemonie syribia7 years ago
Your picture looks on the alkaline side as compared to the chart, and I know vinegar will give you the pH 1 red - I don't trust that chart. L
The pKa of Vinegar (acetic acid) is 4.7 (depending on temperature.) I think the actual pH of common household vinegar is somewhere around 2.5.

But the problem is that vinegar strengths depend on what they are designed for (salad, pickling, etc...)

Good question though. It's important to find solutions and questions that are posed by a problem
lemonie syribia7 years ago
I looked again, "I made solutions of NaOH or HCl in water" - no buffers...? I have a red cabbage, might test something myself. L
Both HCL and NaOH do have a certain pKa. They will buffer but the constant of dissociation is high/low (I can't remember which way it goes.) But in practical terms, there is no real effective buffering terms for biological systems.
syribia (author)  lemonie7 years ago
Yes you are right, it seems they made the scale without use buffer solutions, but I looked over the net and I found other sites that describes red cabbage indicator. However you will notice that all scales are slightly different. Maybe it depends of the content of anthocyanins in the red cabbage and because is a natural product, I’m sure that the anthocyanin content of the cabbage depends of different factors like season.

I’m sorry I didn’t pay to much attention to red cabbage indicator because the objective of my instructable was fermentation process and I designed this to be a qualitative demonstration but I think it could be very interesting to make a serious pH scale of red cabbage juice.

You can see the colors I obtained using different solutions in step 4 (I added notes to the picture so you can now what I used to get these colors.) But some colors like blue are very difficult to get (I got a nice blue color but it lasted only a few seconds)

If you make your scale please let me know

Here are the links I found

http://www.bottlebiology.org/investigations/kimchee_explore.html

http://www.funsci.com/fun3_en/acids/acids.htm#8

http://www.chm.bris.ac.uk/webprojects2002/anderson/acidsbases.htm

http://www.cchem.berkeley.edu/demolab/demo_txt/CabbIndic.htm

http://www.uni-regensburg.de/Fakultaeten/nat_Fak_IV/Organische_Chemie/Didaktik/Keusch/D-cabbage-e.htm

http://wwwchem.csustan.edu/chem3070/images/cabbage.gif

lemonie syribia7 years ago
Thanks, if I can get some solutions of which I'm sure of pH I'll do something (doesn't seem likeley at the moment though...) L
Frogz7 years ago
simple idea to make a better lid(not as safe though although it'd last alot longer) punch a hole through a mason jar lid and glue the tube into place
Punkguyta7 years ago
Pretty nifty, I'm sure there's a lot of people that have no idea what's behind fermentation other than it makes you drunk and bubbles. Thanks for the instructable. -Punk