Chemistry report 'fermentation'
Kasper Goosen & Lucas Breedt, 5vc
Summary
Fermentation is the chemical process in which sugars ferment into ethanol and
carbon dioxide. Yeast is the organism that provides the fermentation.
Our goal is to find out the differences in the amount of carbon dioxide produced
when using different sugars. Therefore we used the sugars glucose, sucrose and
fructose, and measured the amount of carbon dioxide that was developed in three
days time. We found different amounts for different molecular formulas.
Introduction
The fermentation of sugar into ethanol and carbon dioxide goes this way:
C6H12O6 (s) -> 2 C2H6O (l) + 2 CO2 (g)
We expect that the amount of carbon dioxide produced will be different for each type
of sugar, since each sugar has a different building and/or a different molecular
formulas. That way it could either go faster or slower. It is hard to say which sugar
will produce the most carbon dioxide though, because we don’t have knowledge of
which are the best conditions for the fermentation process.
Experimental procedure and approach
First of all we made solutions for the different types of sugar in water. We made a
solution of 375 ml with 67,5 gram sugar. This is a solution of 15,2 percent, and we
used the same proportions for each sugar. We put the solutions into Erlenmeyers,
which we filled to the top (275ml). We did that to make sure almost no oxygen was
present in the Erlenmeyer. Oxygen can ruin the fermentation process (it can make
the sugar oxidate), so it was important we made the amount of oxygen present as
low as possible. Finally, we added three grams of yeast.
We measured the amount of carbon dioxide by using a special set-up. The
Erlenmeyers were closed with a cap, expect for a small tube. This tube led into a
small measuring cup. This measuring cup lay upside down in a larger measuring cup,
which was filled with water. The tube which was connected to the Erlenmeyer went
underwater into the small cup. What will happen during the fermentation: the carbon
dioxide that is formed in the Erlenmeyer will rise into the tube. Eventually, it will end
up in the small measuring cup. In that cup, it will put pressure on the water, so the
water rises. You can measure the amount of carbon dioxide by looking at how high
the water level was before the fermentation process and after. That is the amount of
carbon dioxide formed during the process.
Results
After three days we checked the results of the fermentation process. By comparing
the height of the water afterwards to the height at the beginning we could see how
much carbon dioxide was formed.
Type of sugar
Height before Height after
fermentation fermentation
Difference in
percentage
86 ml
Carbon
dioxide
developed
6 ml
Fructose
80 ml
Glucose
110 ml
118 ml
8 ml
7.2%
Sucrose
140 ml
172 ml
32 ml
22.9%
7.5%
So it’s clear that sucrose has the largest amount of carbon dioxide change, both in
numbers and percentages.
Conclusion and discussion
As you can see we have different beginning heights. This has no special reason
whatsoever, this just has to do with how much water we added in the large cup. This
does not, however, matter for the final results. What we can see is that the carbon
dioxide production is the largest with the sucrose. This means that the amount of
carbon dioxide produced is definitely dependent of the type of sugar used.
If we look at the molecular formulas, we can see that the formula of both both
sucrose and fructose is C6H16O6. The formula of sucrose, however, is C12H22O11.
So sucrose has got larger molecules, which could make the fermentation process go
easier, or perhaps a larger amount of carbon dioxide is developed during the
fermentation of one molecule because of the size of the molecule.
The method we used to measure the amount of carbon dioxide formed in the
fermentation process is probably not the best nor the most accurate method to do
this, and there should be a more precise way to measure the amount of carbon
dioxide. It could be that not all the carbon dioxide ended up in the cup where we
wanted it to. Perhaps some stayed behind in the tube, or leaked out because of the
high amount of pressure caused by the fermentation. It is also a bit hard to say what
the water level is exactly. But we do not know a better method.