How are the concentrations of sugar affect the amount of alcohol produced after
fermentation of yeast?
Anaerobic respiration in yeast is known as fermentation. Yeast
is a fungal microorganism that remains a common component of modern wine and
bread manufacture. Fermentation is the scientific process that yeast metabolizes
sugars and releases alcohol and carbon dioxide. Yeast contains enzymes that catalyze the
breakdown of glucose to ethanol and carbon dioxide.
Fruits can also use to made alcohol (ethanol) instead of pure
glucose when the incomplete level of oxygen occurs. Alcohol can be made from
any fruits that contend starch or sugar. In this experiment we will be using
pineapple juice as sugar for fermentation.
Pineapple contains sucrose, glucose and fructose, which
can undergo fermentation. Also pineapple is really easy to extract its juice
since it really juicy, therefore, it doesn’t need to add water when blending it
that make the concentration of pineapple juice more concentrated.
Cell respiration involves the production of ATP using energy
released by the oxidation of glucose and the first stage of cell respiration
for glucose as a substance is a metabolic path way called glycolysis. Glucose
is partially oxidized in the pathway and a small amount of ATP is produced. The
glycolysis process can be achieved without using oxygen therefore the
glycolysis can form part of both aerobic and anaerobic respiration. Glycolysis
converts one glucose into two pyruvates. Two ATP molecules are used per glucose
and four are produced so there is a net yield of two ATP molecules. This is a
small yield of ATP per glucose, but it can be achieved without the use of any
oxygen, which is anaerobic respiration. Two NADs are also converted into two
reduced NADs. The pyruvates form glycolysis can be ferment to form ethanol and
carbon dioxide and this process occur without using oxygen. As shown in the
chemical equation below:
After fermentation, the solution will contain excess yeast
and won’t be a pure ethanol; therefore, extraction will be required by the
process call distillation. Distillation is the method that separates liquid
from a mixture of liquid by using the different boiling point of the liquid.
Liquids have a different boiling points therefore they vaporize at different
temperature. Distillation is commonly used to separate ethanol that has boiling
point at 78.
A small change of the temperature can affect the product that produced. Then
the alcohol produced can be measure by using hydrometer. Hydrometer uses to
measure a characteristic of liquid such as the specific
gravity (weight per unit volume compared with water). In this
experiment the data collected need to be calibrate to percentage by using ,
start gravity is the pineapple juice before ferment and final gravity is
pineapple juice after ferment and distilled to get a ethanol.
This experiment will be investigating one factor that have an
impact on fermentation rate and amount of ethanol product which is
concentration of sugar that contain in pineapple juice.
Concentration of pineapple juice (100%, 80%, 60%, 40%, 20%)
The amount of alcohol that produced (in %)
Amount of yeast
has an enzyme called zymase and this catalyses the fermentation process. The
more amount of yeast the faster reaction, which might impact the amount of
alcohol, produce in specific time.
electronic balance to measure the amount of 5 grams of yeast because
electronic balance is really accurate, therefore, amount of yeast added will
be likely the same.
Amount of pineapple
amount of pineapple juice is mean the amount of sugar, which effect the
amount of ethanol produced. Yeast consumes sugar to release ethanol and
carbon dioxide therefore the more sugar the more ethanol produced.
the same amount of pineapple juice in every concentration to keep the
independent variable as a concentration of pineapple juice.
pineapple might give different amount of sugar. Some pineapple can be sweeter
pineapple juice from the same pineapples in every trials and concentrations.
longer the fermentation the higher amount of ethanol produced.
3 days of fermentation, all fermented pineapple juice need to be distil
within the same day otherwise the experiment result will not be accurate
temperature has an affect on rate of reaction and amount of ethanol produced.
The high the temperature the faster the rate as well as the amount of ethanol
the fermentation store all the solution in the same place at room
distillation is really important to keep constant. The change in temperature
can affects the product of distillation because all liquids have their own
boiling point and the increase and decrease in temperature might vaporize the
liquid that we don’t want.
really hard to keep the temperature constant throughout the experiment,
therefore, keep the temperature in the range of 77-82 which is close to 78 of ethanol boiling point but does not reach
others liquids boiling points.
The more concentrated pineapple juice, the more sugar
contained. In the higher concentrated pineapple juice, the higher amount of
ethanol produced due to the higher rate of fermentation of yeast.
Knife and chopping board
300 mL Beakers
1000 mL Beaker
100 mL measuring cylinder
Peal and cut pineapple into small pieces
Put all the pineapple in the blender and blend
it until the pineapple become puree then put it in the filtered to percolate the
pineapple garbage and store the pineapple juice in 1000 mL beaker. Make sure
that the pineapple juice doesn’t have anything in it.
Dilute the pineapple juice into 5 concentrations
by adding the distilled water using the measuring cylinder to measure and mix
it together in amount that shown in a table below:
Pineapple juice (mL)
Distilled water (mL)
*Mix the pineapple juice and distilled water in 300 mL beaker.
Take a sample of pineapple juice in each
concentration before add the yeast, place the hydrometer and record the
Use measuring cylinder to measure 200 mL of
pineapple juice for 5 concentrations using 100 mL measuring cylinder and pour
in the 5 different 300 mL beakers.
Weigh 5 grams of yeast power using electronic
balance with electronic balance and pour 5 grams of yeast in each beaker for
each concentration and make sure that the yeast power goes in at the same time.
Mix the yeast and pineapple juice with the
stirring rod until the solution completely mixed.
Cover the beakers with Para film to prevent
other substances to fall in and make a small hole on the film for the gas
produced (carbon dioxide gas) to move out and prevent the burst of high pressure
Keep the beakers close for 3 days to let the
3 days, stir the solution and pour the solution in the distillation flask. Make
sure that the solution doesn’t go over two thirds of the flask to prevent the
solution that might propel into the condenser, compromising the purity of the
11. Place the flask in the thermo well
heat source and set up the distillation as the diagram below:
the temperature and keep in constant at 77-82 (ethanol boils at 78 )
13. When the product of distillation reaches 100
mL in receiving flask remove the heat source.
14. Repeat the process of distillation for all
concentrations and all concentrations in the same trial need to distil in the
steps 4-13 for trial 2 and trial 3.
16. Place all the distilled solutions in the ice
bath and wait until the temperature lower and reach 15 (temperature that hydrometer work best)
the hydrometer in each solution and record the final gravity.
18. All the solutions, chemical, and waste from
the lab can pour it in the sink since it’s not toxic and won’t have any effect
to the environment.
– The bubble that formed after the fermentation shows that
the fermentation is really occur since bubbles formed by the carbon dioxide
Calculation the percentage of ethanol using equation:
Uncertainty of starting gravity =
Uncertainty of final gravity =
Total uncertainty = 0.001 +0.001
% Of ethanol
Calculate the average of % of
pineapple juice (%)
% Of ethanol
As the graph shows as the concentration of pineapple juice
increase the percentage of ethanol produced after yeast fermentation increase.
This graph shows clear trend along with the coefficient of determination of 0.99, which means that the data fits the
trend line of equation .
The value of is really close to 1 shows that the data has a
low percentage of variation. The error bars on the graph also show the low
spread of data since the data collected are close to its averages. The max-min
error bar on the graph is not overlap also shows that the data is significant.
In this experiment, the data show the impact of concentration
of pineapple juice on the amount of percentage of ethanol produced which follow
the hypothesis as the higher concentrated pineapple juice, the higher amount of
ethanol produced due to the higher rate of fermentation of yeast. The graph of
the average percentage ethanol produces for each concentrations of pineapple
juice also show a clear trend as the amount of ethanol produced increase along
with the concentration of pineapple juice. The graph also shows that the data
fits with the trend line with a coefficient of determination of 0.99. As yeast
degrading the glucose in pineapple juice into ethanol and carbon dioxide by
fermentation (anaerobic respiration). I
can conclude that this experiment shows that the concentrations of sugar affect
the amount of alcohol produced after fermentation of yeast.
The data collected is reliable as the error bar shows a
really low spread of data, which means that the data are close to the average
and a reliable of the mean value as a representative number for the data set.
The error bar also show a significant difference of the data, as it shows on
the graph the errors bars are not overlap, therefore, the differences are
likely to be significant. The data averages and the trend line are also fit
well so it’s clearly shows that the data follow my hypothesis. Including a
really small uncertainty of of
ethanol produced, I believed that my experiment at this stage is reliable.
My experiment have limitation of time, therefore, I didn’t
had a chance to do the trials up to 5 trials to make my data more reliable. The
distillation took at least one hour for each concentration for each trial so
the random error occurs at this stage due to the limitation of distillation
tools in my lab. I was able to distill the ethanol 2 concentrations at the time
so the fermented pineapple juices that need to wait for distillation had longer
fermentation time. The best I could do was distilled all the solutions in the
same trial in the same day. To improve this random error, I might need to get
more laboratories equipment to distill all the fermented solution at the same
time or I could start the fermentation and distill at different time so I can
distill the solution that first fermented up to the date first. Also the
distillation temperature is really hard to keep exact at 78 so the temperature was in the range between
which might have an impact on the extraction of ethanol. This can be solving by
using thermo well heat source that can set the temperature at specific
Furthermore, this experiment can be use to compare a sugar
concentration of different fruits by using the fermentation method. The higher amount
of ethanol produce will be the numbers that can be used to compare the sugar
concentration as the higher concentration of sugar contain the higher amount of