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NAME : NIK MUHAMMAD FIRDAUS BIN AHMAD
CLASS : MO9H
DATE OF PRACTICAL : 27TH JANUARY 2011
INTRODUCTION :
For the first production of bread, the dough is mixed with
Saccharomyces (yeast) .
this microbes will act on the sugar in the dough, by anaerobic
cell respiration will producing
ethanol and carbon dioxide. This carbon dioxide will form
bubbles that make the dough rise
and become less dense, lighter and increasing its volume. When
baking in the oven, the
microbe, Saccharomyces is killed because of excessive heat which
stop fermentation process
meanwhile the ethanol produced is evaporates. Warm temperature
is preferable for the yeast
to perform at the optimum temperature.
RESEARCH QUESTION :
How does applying various temperatures need to heat the dough
(27 0C, 50 0C ,70 0C)
affect the volume of dough increase for each 5 minutes interval
that indicate the
Saccharomyces bacteria activity on the dough?
VARIABLE:
Unit Range
Independentvariables
The temperatureneed to heat the
dough
0C 30 0C, 50 0C ,70 0C
DependentVariables
Volume of the doughincrease for every 5
minutes intervalCm3 > 0.00 cm3
Table 1 : table shows the independent and dependent variable
with their unit and range used
in the experiment.
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Controlledvariable
Possible effects onresult
Ways to control variable
The volume of
water used.
(ml)
If the volume of each
water solution is not the
same, it will affected the
rate of reaction between
the yeast and the dough
which can be less or
higher.Excessive volume of
water will not allow the dough
to rise. Too little will make the
hard. Hence, to obtain an
accurate result the volume of
water should be kept at
constant volume.
By using measuring cylinder,take about fixed 10.00 ml of
water solution for each
temperature/test tube. This
is to make sure that all test
tubes have the same and
accurate amount of water.
The species of
Saccharomyces cell
used
Different species may contain
different respiration rate.
Hence, to enable a good result
the species of the
Saccharomyces is taken from a
similar place.
The origin of the Saccharomyces
cell is taken from a similar source.
The time
interval for each
testing is being
synchronized
(min)
If the time interval is not
same for every test tube,then, then the rate ofreaction between
yeastand the dough will be
less precise andaccurate. It make the
measurement oftemperature will be more
or less than the actualtemperature need for aspecific time, thus
it will
affected the rate of yeastactivity from the volumeof the dough
increase.
To make sure that the resultobtain is not affected, the
time interval need to be
constant which is 5 minutes/
300 second for each interval
by using stopwatch for each
temperature. This is to make
sure that the rate of yeast
activity for the all
experiments is calculatedprecise and accurately.
The air
movement,
condition of
surrounding
where the
experiment take
place,
If the air movement isnot same for eachexperiment it will
affected the temperatureof the enzyme. Thus itwill affected the
rate of
enzyme activity
For each
experiment/temperature
should be conducted at the
same place and same
surrounding condition which
is in a clossed room. This is
to make sure that the
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condition and surronding
environment did not affected
the temperature of enzyme.
Controlled
variable
(continued)
Possible effects onresult
Ways to control variable
The weight of yeast
used (g)
To much yeast will result in
higher dough level due to more
carbon dioxide gas released and
vice versa. Hence, the amount
of yeast cell contain in each
dough is kept constant
An electronic balance is used to
ensure, approximately 1.00 gram of
Saccharomyces (yeast cells) is to beused in each experiment.
The weight of
glucose used (g)
Too much glucose used will
provide the yeast more
substrate and hence increase
respiration. Thus, it will release
more carbon dioxide as product
vice versa. Therefore, to
maintain an accurate reading,
the weight of glucose is kept at
constant.
An electronic balance is used to
ensure, approximately 1.00 gram of
glucose is to be used for everyexperiment.
Table 2: table shows the controlled variable that need to be
constant throughout the
experiment with the possible effect if the variable not constant
and ways to control the
variable
HYPOTHESIS:
Changes in temperature affect the volume of the dough that
indicates theactivity of yeast on dough. The action of yeast
depends on thetemperature.
At low temperature, the rate of yeast activity will take place
slowly.
The rate of activity of yeast on dough increase with the
increase intemperature until it reaches the optimum temperature
which is thetemperature at which an enzyme in the yeast catalyses a
reaction at the
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maximum rate. There is an enzyme inside the yeast itself that
will perform well in anoptimal temperature indicating an increase
in dough level
Beyond the optimum temperature, any increase in temperature
causesthe rate of yeast activity to decrease sharply until it stops
completely at
the temperature where the yeast is said to be denatured. Below
the optimumtemperature will decrease the ability of the enzymes in
the yeast to catalyse the reaction.
APPARATUS AND MATERIALS:
No Apparatus Quantity
1 10ml measuring cylinder (+ 0.05ml) 4
2 Plastic meshing bowl 1
3 Glass rod 3
4 Beaker 3
5 Electric iron kettle 1
6 Water bath 2
7 Thermometer (+ 0.5 0c) 4
Table 3:table shows the apparatus used in the experiment with
its quantity
No Materials Quantity
1 Yeast -depend-2 Water -depend-
3 Glucose -depend-
4 Flour -depend-
Table 4: table shows the materials used in the experiment with
its quantity.
METHODOLOGY :
Refer to the attachment.
DATA COLLECTION:
QUALITATIVE DATA:
1. The dough gives out pungent smell as the yeast smell is
pungent.
2. The colour of the dough is pale-brown.
3. The colour of the yeast used was brown.
4. The shape of the dough is irregular.
5. When the dough is being added with the yeast and glucose, the
air bubble producefrom the dough.
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6. When the dough is being added with the yeast and glucose, the
dough will rise in
every time interval. But the growth of the dough will stop at
certain time interval.
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QUANTITATIVE DATA:
Data Collection:
Temperature 30 : Normal yeast
Time,
Trial 1 Trial 2 Trial 30 16 14 175 16 15 1810 17 17 1915 19 19
2020 20 20 2025 21 21 2030 21 21 2135 22 21 2240 22 22 2245 22 22
2350 22 22 2355 22 22 2360 22 22 23
Table 5.1: table shows the changes of volume of dough against
time intervals for 60 minutes
for unboiled yeast ( Saccharomyoces)
Temperature 50 : Normal yeast
Time,
Trial 1 Trial 2 Trial 30 15 14 155 17 19 1710 18 20 1815 19 20
1920 20 21 2025 21 21 2030 21 21 2035 21 21 20
40 21 21 2045 21 21 2050 21 21 2055 21 21 2060 21 21 20
Table 5.2: table shows the changes of volume of dough against
time intervals for 60 minutes
for unboiled yeast ( Saccharomyoces)
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Temperature 70 : Normal yeast
Time,
Trial 1 Trial 2 Trial 30 15 12 165 17 13 1710 18 14 1715 19 13
1720 20 13 1725 21 13 1730 21 13 1835 21 14 1840 21 14 1845 21 14
1850 21 14 1855 21 14 1860 21 14 18
Table 5.3: table shows the changes of volume of dough against
time intervals for 60 minutes
for unboiled yeast ( Saccharomyoces)
Temperature 30 : Boiled yeast
Time,
Trial 1 Trial 2 Trial 3
0 14 16 155 14 17 1510 14 17 1515 14 17 1520 14 17 1525 14 17
1530 14 17 1535 14 17 1540 14 17 1545 14 17 1550 14 17 15
55 14 17 1560 14 17 15
Table 6.1 :table shows the changes of volume of dough against
time intervals for 60 minutes
for boiled yeast ( Saccharomyoces.)
Temperature 50 : Boiled yeast
Time,
Trial 1 Trial 2 Trial 30 16 14 17
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5 17 14 1710 17 14 1815 17 14 1820 17 14 1825 17 14 18
30 17 14 1835 17 14 1840 17 14 1845 17 14 1850 17 14 1855 17 14
1860 17 14 18
Table 6.2 :table shows the changes of volume of dough against
time intervals for 60 minutes
for boiled yeast ( Saccharomyoces.)
Temperature 70 : Boiled yeast
Time,
Trial 1 Trial 2 Trial 30 15 15 145 15 16 1410 15 16 1415 15 16
1520 15 16 15
25 15 16 1530 15 16 1535 15 16 1540 15 16 1545 15 16 1550 15 16
1555 15 16 1560 15 16 15
Table 6.3 :table shows the changes of volume of dough against
time intervals for 60 minutes
for boiled yeast ( Saccharomyoces.)
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DATA PROCESSING :
1. Calculate the average reading of the changes of volume of
dough for each time
interval for boiled and unboiled yeast
In order to calculate the average reading of the changes of the
volume of dough for each time
interval are obtain by using the formula below:
Average =
For example, the average temperature for the first interval
(first five minute) for unboiled
Saccharomyoces at 30C is
Average =
= 15.333 (rounded to the nearest digit)
= 15.0 cm3
Other average reading of the of the changes of the volume of
dough for each time interval are
obtain by using the same formula and all the result are recorded
in the table below:
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Table 7: table above show the average rise level of the dough by
using the
measuring cylinder for the unboiled yeast.
Temperature/oC
( 0.5 oC )
Trial Volume of dough/cm3 (0.5 cm3) against time intervals/s (
0.5 min )
0 5 10 15 20 25 30 35 40 45 50 55 60
30.0 1 15.
0
19.
0
26.
0
27.
0
30.
0
30.
0
31.
0
32.
0
32.
0
32.
0
32.
0
32.
0
32.0
2 15.
0
24.
0
29.
0
31.
0
31.
0
31.
0
31.
0
31.
0
31.
0
31.
5
32.
0
32.
0
32.0
3 16.0
23.0
25.0
26.0
27.0
27.0
27.0
26.0
26.0
26.5
32.0
32.0
32.0
Average 15.
3
22.
0
26.
7
28.
0
29.
3
29.
3
29.
7
29.
7
29.
7
30.
0
32.
0
32.
0
32.0
50.0 1 10.
0
12.
0
15.
0
16.
0
17.
0
18.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.
019.0
2 10.
0
12.
0
16.
0
19.
0
22.
0
23.
0
24.
0
25.
0
26.
0
27.
0
27.
0
27.
027.0
3 11.
0
12.
0
16.
5
17.
0
20.
0
21.
0
21.
0
23.
0
23.
0
23.
0
23.
0
23.
023.0
Average 10.
3
12.
0
15.
8
17.
3
19.
7
20.
7
21.
3
22.
3
22.
7
23.
0
23.
0
23.
0
23.0
70.0 1 16.
5
19.
0
20.
0
20.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.0
2 13.
0
16.
0
16.
0
15.
0
15.
0
15.
0
15.
0
15.
0
15.
0
15.
0
15.
0
15.
0
15.0
3 11.
5
21.
0
21.
0
21.
0
19.
5
19.
0
18.
5
18.
5
18.
5
18.
5
18.
5
18.
5
18.5
Average 13.
7
18.
7
19.
0
18.
7
17.
8
17.
7
17.
5
17.
5
17.
5
17.
5
17.
5
17.
5
17.5
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Table 8: Table of average changes of volume of dough against
time intervals for 60 minutes
for boiled yeast
Temperature/oC
( 0.5 oC )
Trial Volume of dough/cm3 (0.5 cm3) against time intervals/s (
0.5 min )
0 5 10 15 20 25 30 35 40 45 50 55 60
30.0 1 14.
0
14.
0
14.
0
14.
0
14.
0
14.
0
14.
0
14.
0
14.
0
14.
0
14.
0
14.
0
14.0
2 18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.0
3 16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.0
Average 16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.
0
16.0
50.0 1 24.
0
24.
0
24.
0
24.
0
24.
0
24.
0
24.
0
24.
0
24.
0
24.
0
24.
0
24.
0
24.0
2 18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.0
3 19.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.
0
19.0
Average 20.
3
20.
3
20.
3
20.
3
20.
3
20.
3
20.
3
20.
3
20.
3
20.
3
20.
3
20.
3
20.3
70.0 1 13.
0
13.
0
13.
0
13.
0
13.
0
13.
0
13.
0
13.
0
13.
0
13.
0
13.
0
13.
0
13.0
2 18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.
0
18.0
3 17.
0
17.
0
17.
0
17.
0
17.
0
17.
0
17.
0
17.
0
17.
0
17.
0
17.
0
17.
0
17.0
Average 16.0
16.0
16.0
16.0
16.0
16.0
16.0
16.0
16.0
16.0
16.0
16.0
16.0
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Calculations for standard deviation
1. To calculate the standard deviation as uncertainties using
GDC TI-84 Plus students
edition:
Steps to calculate the standard deviation :
(a) On the GDC.(b) Press STAT and ENTER.
(c) Fill in the values of the data in L1.
(d) Press STAT again and then press right arrow by pressing
>.
(e) Then press ENTER twice and you will get the value of
standard deviation which is
notated by Sx.
Standard deviation =
= the frequency ( trials )n = the sample of data
= the sum of all data
Table 9: Table of average changes of volume of dough against
time intervals for 60 minutes
for un-boiled yeast and standard deviation
Temperatur
e/ oC
( 0.5 oC )
Average volume of dough/cm3 (0.5 cm3) against time intervals/s (
0.5 min )
0 5 10 15 20 25 30 35 40 45 50 55 60
30.0 15.3
0.471
22.0
2.16
26.7
1.70
28.0
2.16
29.3
1.70
29.3
1.70
29.7
1.89
29.7
2.62
29.7
2.62
30.0
2.48
32.0
0.000
32.0
0.000
32.0
0.000
50.0 10.3
0.471
12.0
0.000
15.8
0.624
17.3
1.25
19.7
2.05
20.7
2.05
21.3
2.05
22.3
2.50
22.7
2.87
23.0
3.27
23.0
3.27
23.0
3.27
23.0
3.27
70.0 13.7
2.09
18.7
2.05
19.0
2.16
18.7
2.62
17.8
2.01
17.7
1.89
17.5
1.78
17.5
1.78
17.5
1.78
17.5
1.78
17.5
1.78
17.5
1.78
17.5
1.78
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Table 10: Table of average changes of volume of dough against
time intervals for 60 minutes
for boiled yeast and standard deviation
Key:Series Condition Temperature
1 Un-boiled yeast 30oC
2 Un-boiled yeast 50oC
3 Un-boiled yeast 70oC
Temperature/oC
( 0.5 oC )
Volume of dough/cm3 (0.5 cm3) against time intervals/s ( 0.5 min
)
0 5 10 15 20 25 30 35 40 45 50 55 60
30.0 16.0
1.63
16.0
1.63
16.0
1.63
16.0
1.63
16.0
1.63
16.0
1.63
16.0
1.63
16.0
1.63
16.0
1.63
16.0
1.63
16.0
1.63
16.0
1.63
16.0
1.63
50.0 20.3
2.62
20.3
2.62
20.3
2.62
20.3
2.62
20.3
2.62
20.3
2.62
20.3
2.62
20.3
2.62
20.3
2.62
20.3
2.62
20.3
2.62
20.3
2.62
20.3
2.62
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Key:
Series Condition Temperature
1 Boiled yeast 30oC
2 Boiled yeast 50oC
3 Boiled yeast 70oC
Calculations of rate of change of volume of dough
Table 11: Table of rate of change of volume of dough for
un-boiled yeast
Temperatur
e/ oC
( 0.5 oC )
Rate of change of volume of dough (cm3 min-1)
0 5 10 15 20 25 30 35 40 45 50 55 60
30.0 0.000 4.40 2.67 1.87 1.47 1.17 0.99
0
0.84
9
0.74
3
0.66
7
0.64
0
0.57
6
0.52
2
50.0 0.000 2.40 1.58 1.15 0.98
5
0.82
8
0.71
0
0.63
7
0.56
8
0.51
1
0.46
0
0.41
8
0.38
3
70.0 0.000 3.74 1.90 1.25 0.89
0
0.70
8
0.58
3
0.50
0
0.43
8
0.38
9
0.35
0
0.31
8
0.29
2
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Table 12: Table of rate of change of volume of dough for boiled
yeast
Calculations for uncertainty of rate of change of volume of
dough
Table 13: Table of uncertainty of rate of change of volume of
dough for un-boiled yeast
Temperatur
e/ oC
( 0.5 oC )
Rate of change of volume of dough (cm3 min-1)
0 5 10 15 20 25 30 35 40 45 50 55 60
30.0 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.000 0.000 0.000
50.0 0.000 0.000 0.000 0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
70.0 0.000 0.000 0.000 0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
Temperatu
re/ oC
( 0.5 oC )
Rate of change of volume of dough (cm3 min-1)
0 5 10 15 20 25 30 35 40 45 50 55 60
30.0 0.000
0.000
4.40
0.540
2.67
0.184
1.87
0.09
57
1.47
0.61
8
1.17
0.04
33
0.99
00.
332
0.84
90.
0264
0.74
30.
0218
0.66
70.
185
0.64
00.
0164
0.57
60.
0143
0.52
20.
0127
50.0 0.000
0.000
2.40
0.340
1.58
0.129
1.15
0.07
16
0.98
50.
0496
0.82
80.
0366
0.71
00.
0285
0.63
70.
0234
0.56
80.
196
0.51
10.
0168
0.46
00.
0146
0.41
80.
0129
0.38
30.
0115
70.0 0.000
0.000
3.74
0.474
1.90
0.145
1.25
0.07
51
0.89
00.0473
0.70
80.0342
0.58
30.0264
0.50
00.0214
0.43
80.0180
0.38
90.0154
0.35
00.0135
0.31
80.0120
0.29
20.0108
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Table 14: Table of uncertainty of rate of change of volume of
dough for boiled yeast.
Key:
Series Condition Temperature of bath, T (oC)
A Un-boiled yeast 30.0
B Un-boiled yeast 50.0
C Un-boiled yeast 70.0
D Boiled yeast 30.0
E Boiled yeast 50.0
F Boiled yeast 70.0
Temperatur
e/ oC
( 0.5 oC )
Rate of change of volume of dough (cm3 min-1)
0 5 10 15 20 25 30 35 40 45 50 55 60
30.0 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.000 0.000 0.000
50.0 0.000 0.000 0.000 0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
70.0 0.000 0.000 0.000 0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
0
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Graph Analysis:
The highest rate of increment can be seen for the Series B which
is the un-boiled yeast placed
in 50oC bath. The rate for other un-boiled yeast also shows an
increment before dropping
along with the others.
DATA DISCUSSION
Yeast will act on the sugar in the dough by anaerobic
respiration and producing the
carbon dioxide and ethanol.The air bubble produce when the dough
are mix with the
yeast actually is the carbon dioxide gas.
Yeast activity will increase if it is supplied with warm
temperature. If the temperature
supplied is favourable enough for the yeast to conduct its
activities, it will perform at
optimum rate.
Refer to the graph 1, for unboiled yeast, the level of rise of
the dough is almost thesame for every temperature which is 28C, 50C
and 70C for the unboiled yeast
experiments. The yeast that supplied with 50C is have a more
higher constant level
of rise of the dough. For 28C, the dough level increase slowly
compared to the 50C
and 70C. For the 70C, the dough level increase and then start to
drop at time interval
of 30 minutes.
For graph 2, the result is likely same with the graph 1, where
the higher increase in
temperature that is constant still 50C. The 70C increase but at
certain time, the level
rise of the dough drop. By comparing both of the graph, the
optimum temperature for
the yeast to perform at its optimum rate is 50C.
For graph 3, it is show that for all the temperature, the rate
of increment are the
highest at the first 15 minutes time interval. This is because
the yeast are completely
used by the dough to be fermented so that it can produce high
carbon dioxide to make
large increment of the dough volume.
For graph 3, it is show that the rate of increment are at best
level using 50 0c because
the rate of increment are 0 cm3min-1 starting 30 minute interval
which indicates that
all the glucose in dough are used by the yeast to be fermented
for producing carbon
dioxide and ethanol.
Graph of rate of increment of the dough against the time
interval for the boiled yeast
cannot be plotted because there is no exact increment of the
dough for each timeinterval which means that rate of increment
cannot be calculated. This means that
yeast cannot function at all after boiled because the enzyme
inside the yeast is
denatured already. Hence no reaction happened between the dough
and the yeast.
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8/6/2019 Experiment Dough Bio Saya
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DATA EVALUATION:
LIMITATIONS AND SUGGESTIONS
Firstly,he size of the dough when insert into the measuring
cylinder is not in spherically
shape. The shape of the dough in not same for every experiment.
This make some dough have
difficulties in decide the level rise because of this
limitation. In order to curb this problem, we
can use a a fix mould, the shape of the dough can be fix for all
experiments. This can prevent
the limitation of irregular shape of the dough and enable to
measure the level rise more
accurately.
Secondly, it is quite hard to maintain the temperature 50C and
70C using the conventional
method. There are possibility that the temperature might be
higher or lower than the exact
temperature required. This can affect the rate of enzyme
reaction in the experiment.Therefore, we can use the electronic
water bath for the 70C and 50C temperature
experiment. This is because the temperature is maintained
efficiently by the electronic water
bath
Thirdly, is parallax error might occur while measuring the
volume of dough using the
measuring cylinder. If the parallax error happened the reading
might be higher or lower than
the exact volume required. This can affect the rate of enzyme
reaction in the experiment.So,
students have to make sure that the observer eyes parallel with
the meniscus point of the
solution, so that the precise and accurate reading can be
obtained.
Fourthly, there are possibility that the heat from conductor
hand might be transferred to the
test tubes when conducted the experiment. This will affect the
temperature of reactant. The
temperature taken might be higher or lower than the exact
temperature required. This can
affect the rate of yeast reaction in the experiment. To reduce
the effect we can use a clipper to
hold the test tube to avoid heat from our hand being transferred
to the test tubes.
Fifth, is the standard deviation for the boiled yeast experiment
cannot be calculated because
they do not have any trials readings. So, to get a more accurate
results, taking three or more
trials can make standard deviation of the boiled yeast for every
experiment can be calculate
accurately.
.
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8/6/2019 Experiment Dough Bio Saya
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CONCLUSION :
Temperature is one of the factor that affect the yeast activity.
Theoptimum temperature for enzyme activity in the yeast or the rate
of yeastreaction is 50C. The amylase enzyme is less active at the
temperature,30
C and denatured at the temperature of 70C.
The rate of activity of yeast on the dough are very low at the
lowtemperature which is 30C .At low temperature, the enzyme in
yeast isnot so active, therefore the yeast react slowly on the
dough
As the temperature is increase the rate of yeast activity on the
dough isalso increasing. An increase in temperature causes more
frequentcollisions between the yeast and dough molecules. Hence the
rate ofyeast activity on dough increases.
The rate of yeast activity on the dough are at the maximum rate
when atthe 50C. This is the optimum temperature where the yeast is
react at thefastest to fermented the dough. At this temperature,
the fermentation ofdough is completed in the shortest period.
The rate of amylase enzyme activity on the starch are decreasing
whenthe temperature is beyond 50C which is the optimum temperature
andstop when at the temperature is 70C. This is because at
hightemperature, yeast are killed. Thus the rate of yeast activity
to bedecreases .
The hypothesis is accepted.
REFERENCE
1. IB Biology guidebook
2. Biology Handbook
3. Biology course companion
