Post on 24-May-2015
TBC 3013
INFORMATION AND COMMUNICATION TECHNOLOGY IN BIOLOGY
THE MORE THE MERRIER
Bacterial Fermentation
GROUP MEMBERS:
NAME MATRIC NUMBER
AZFATINI BT NAWI D20081032320
ZETY LIYANA BT ZAINAL ABIDIN D20081032351
SYAFIQAH BT SHAARI D20091034830
YIP SOOK HAN D20091034841
LETCURER: ASSOC PROF DR SOPIA MD YASSIN
Class: 4 Science 1
Time: 7.40 a.m. – 9.00 a.m.
Theme: Physiology of Living Things
Learning Area: Development of Technology in Food Processing
Learning outcome: Relate food processing methods with factors causing food spoilage.
Phase Content Learning and Teaching Activities Notes
Engage Refer to Appendix A - Teacher gets students ideas on
the causes of food spoilage.
- Students share their prior
knowledge on this issue.
- What happen to the
milk if it is left for 1
day? Why?
Empower Refer to Appendix B - Planning and Doing Experiment
– observation of the change in
pH when the milk is left for 1
day.
- Students get the result and
analyze the data.
- Students relate the reduction of
pH with bacterial fermentation
that causes milk spoilage.
- Teacher explains to students
how bacterial fermentation
reduces the pH of milk and
causing milk spoilage.
- Observation.
- Equipment required:
Data logger
connected to a PC
One pH probe
A bottle of milk
- Analyzing the data.
- A few question
related to the
reduction on pH of
milk.
- Discussion.
Enhance Refer to Appendix C - Teacher gives an example about
milk spoilage and asks students
to give their opinion related to
this issue.
- School Milk
Programme.
SCIENTIFIC CONCEPT
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.
ENGAGE
Appendix A
Before After 1 day
Procedures
Equipment required
Data logger connected to a PC
One pH probe
A bottle of milk
Experiment set up
1. The milk is allowed to reach room temperature without cooking and re-pasteurising it.
2. The pH probe is plug into the data logger socket and the probe is inserted into the
container of milk.
3. The software is run.
4. The experiment is run for 24 hours. The pH is taken at interval of 1 hour.
5. Graph pH versus time (hour) is plotted.
Carrying out the experiment
Data logger is started recording the data and displaying the graph. The experiment is kept in a
stable environment as the extremes in room temperature may give false readings.
EMPOWER
Appendix B
Result
Time (hour) pH
1 5.442
2 5.442
3 5.442
4 5.380
5 5.360
6 5.340
7 5.299
8 5.278
9 5.258
10 5.237
11 5.230
12 5.197
13 5.186
14 5.174
15 5.158
16 5.149
17 5.142
18 5.133
19 5.121
20 5.117
21 5.112
22 5.096
23 5.074
24 5.063
Graph
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 244.8
4.9
5
5.1
5.2
5.3
5.4
5.5
pH versus Time (hour)
pH
Time (hour)
pH
Discussion
Q1. Did you see a reduction in pH shortly after starting the experiment?
A1.This partly depends upon the freshness of the milk but there should be little change at this
stage.
Q2. What causes the change in pH as the milk turns sour?
A2.The lactose in the milk is converted to lactic acid. As the acid level increases the pH level
drops.
Q3. Is the reduction in pH constant over the entire experiment?
A3. No. We can see from our graph the gradient significantly increases half way through for
fresh pasteurised milk.
Q4. Calculate the extent of change in pH obtained during the experiment.
A4. This will partly depend upon the students results. For our graph the milk went through a
change in pH of 1.95 (6.75 - 4.8).
Q5. What do you think will be the result of incubating UHT milk over the same time period?
A5. This question is there to make the students think of the different ways, and reasons for
processing milk. I expect the results to be very stable over the same time period.
ENHANCE
School Milk Program has to be postponed for a time being because the food poisoning case
among students due to milk spoilage. What are the factors causing the milk spoilage and how to
overcome the problems?
UNIQUE FEATURES
i. Low cost because we only use a bottle of milk.
ii. Easy to perform because this experiment only contain one variable which is pH.
iii. By using data logger, we do not need a constant observation. The experiment can be left
and after 24 hours, we can obtain the result.
iv. The result can be analyze and interpreted easily.
v. The graph can be plotted easily.
REFERENCE
Measuring the pH of Milk. Retrieved on 31st August 2010 from http://www.picotech.com/experiments/ph_of_milk/ph_of-milk.html