1. THE MORETHE MERRIER
Bacterial Fermentation
AZFATINI BT NAWI
D20081032320
ZETY LIYANA BT ZAINALABIDIN
D20081032351
SYAFIQAH SHAARI
D20091034832
YIP SOOK HAN
D20091034841

2. SCIENTIFIC CONCEPT
 Fermentation is the conversion of a carbohydrate
such as sugar into an acid or alcohol.
 Fermentation can be performed by yeast and
some types of bacteria.
 Milk is contaminated by bacteria even before it
leaves the udder, although at this point they are
harmless and few in numbers.
 The two main groups of bacteria in milk are Lactic
acids and coliforms. Lactic acid is the normal
bacteria present in milk and dairy products.
Coliforms are the main reason for milk spoilage.

3. ENGAGE
Before After 1 day
A glass of fresh milk was left for one day. It smells
sour and even foul after that. What happen to the
milk?

4. ENGAGE
Planning and Doing Experiment – observation of the
change in pH when the milk is left for 1 day.

5. EMPOWER
Result
Time (hour) pH Time (hour) pH
1 5.442 13 5.186
2 5.442 14 5.174
3 5.442 15 5.158
4 5.380 16 5.149
5 5.360 17 5.142
6 5.340 18 5.133
7 5.299 19 5.121
8 5.278 20 5.117
9 5.258 21 5.112
10 5.237 22 5.096
11 5.230 23 5.074
12 5.197 24 5.063

6. EMPOWER
Graph
4.8
4.9
5
5.1
5.2
5.3
5.4
5.5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
pH
Time (hour)
pH versus Time (hour)
pH

7. EMPOWER
Discussion
1. Observe and explain the change of pH
after starting the experiment from the
graph given.
2. What causes the reduction in the pH of
milk?
3. Describe the speed of change in pH the
whole experiment period?
4. Calculate the extent of change in pH
obtained in the process.

8. ENHANCE
School Milk Program has to be postponed for a time being
because the food poisoning case among students due to milk
spoilage. Based on your opinion, what are the factors that cause
the milk spoilage?

9. UNIQUE FEATURES
By using data
logger, we do not
need to make a
constant
observation.
The slightly changes
in the pH values are
able to be observed.
We do not need to
use pH test papers
during the whole
experiment.

10. REFERENCE
Measuring the pH of Milk. Retrieved
on 31st August 2010 from
http://www.picotech.com/experiments/
ph_of_milk/ph_of-milk.html

11. The End
Thank You