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