065 FERMENTATION (ALCOHOLIC)

1
065 FERMENTATION (ALCOHOLIC)
To demonstrate how yeast converts sugars into
carbon dioxide and ethanol
MATERIALS REQUIRED
One empty bottle / test tube One tumbler warm
water One packet active dried yeast 4
tablespoons sugar One rubber balloon Freshly
prepared lime water
rubber balloon
warm water
bottle
sugar
yeast
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First fill the bottle / test tube with warm
water. Add yeast to it and shake the bottle /
test tubes a few times to mix the yeast with
water. Add the sugar and shake for some more
time. Blow the balloon up slightly and place
over the neck of the bottle / test tube with
gentle care. Let the bottle/test tube sit for
about 30 minutes. In due course of time the
balloon will inflate.
3
Carefully remove the expanded balloon from the
bottle / test tube with great care so as not to
release the carbon dioxide Release the gas
trapped in the balloon into a test tube
containing fresh lime water If the lime water
turns milky it is confirmed that the gas in the
balloon is carbon dioxide
lime water turns milky
4
As the yeast consumes the sugar, it produces
carbon dioxide. The gas initially fills the
bottle/test tube and with no place to go but up,
this gas slowly fills the balloon thereby
expanding it.
The same mechanism occurs while baking bread. The
yeast releases the carbon dioxide gas which
expands and makes many small holes in the bread.
This makes the bread light and fluffy. Bakers
yeast is Saccharomyces cerevisiae