1. DATA LOGGING

2. Introduction
 pH fresh milk (between 6.7 and 6.5)
 Slightly acidic
 Value lower 6.5 (considerable acid taken
place)
 Value higher 6.7 (mastitis infection)
 Litmus paper : indicate pH (test milk activity)
 pH measurement : acceptance test for milk
 Measuring milk acidity is important to
determine milk quality

3.  Advantages data logger :
- Can collect data independently of a computer
- Mistake of misread the data will not happen
- Graphs & tables produce automatically
 Disadvantages data logger :
- Cost of purchasing
- If break down, some data will be lost / not
recorded
- If malfunction, cost needed to repair is
higher
- Drawing skills become weaker

4. Problem statement
Ahmad bought milk from the nearby shop. He
drank in a little amount and then left it on
the table. He forgot to store the milk into
the refrigerator.
The next day, he drank the leftover milk. But,
he found out that the taste was totally
different than yesterday. The milk tasted
sour. He wonders what happened to the milk
when it is left and exposed.

5.  Why does the taste of the milk changes as it
is exposed?
 Is the sour milk acidic or basic?
 If the milk is acidic or basic, what is the pH
value?

6.  Equipment required:
1. Data logger
 Electronic device that records data over time
 Automatically collect data in wide range of time
 Accurate data on the environment conditions
being monitored can be obtained.
Data logger Data logger
compartments

7. 2. pH sensor
 To measure pH of milk.
 Provide automatic data collection.
 Can measure pH from range 0 to 14.
3. Milk

8.  Methodology
1. The milk from bottle is pour into a glass.
2. The milk is then allow to reach the room
temperature without cooking and re-
pasteurising it.
3. The pH probe is plug into the data logger
socket.
4. The pH probe is inserted into the milk.
5. Run the software.
6. All data are recorded and displayed in
graph form.

9. Data logger connected to
PC
pH probe inserted into milk

11.  The reduction in pH can be seen shortly
after starting the experiment.
 When exposed to air, bacteria will start
to grow rapidly contributing to the
sourness of the milk.
 After few days, we can see that the pH
starting to decrease to a lower value.
 Milk contains lactose, but at the same
time milk also contained bacteria.

12.  Some bacteria work efficiently in warm
conditions and causes milk become sour.
 pasteurized milk undergo series of
steps, bacteria are not completely killed
in this process.
 The left bacteria will gradually
reproduce and turns the milk into sour.

13.  The main reason why milk turns sour is
because the lactose in the milk is
converted to lactic acid.
 As the acid level increases, the pH
levels drops. If milk is exposed, the
bacteria in the milk will start to
produce and forms gases and chemicals
which change its smell, taste, texture.

14.  If we incubate UHT milk in a closed
arrangement :
- Provide higher bactericide effect
- Decrease contamination
- Bacteria activity decrease
- Milk become stable (taste)
 If we consume contaminated food :
- Cause by microorganisms
- Cause disease (food borne illnesses)
- Common symptoms : diarrhea, vomit, fever,
jaundice

15.  If we consume food contained higher
acidity :
- Our stomach is an acidic place
- When we eating, acid secreted into the
stomach
(digestion)
- Secretion acid + food (higher acidity)  very
acidity
- Cause : sour tummy / sour stomach, acid
reflux

16.  Reduction in pH is not constant over
entire the experiment,
 From the graph, the gradient significantly
increases half way.
 As the time increases, the pH is reduced.
 Means that acidity increases.
 Milk begins to sour.
 Milk’s sugar  acids (by bacteria)

17.  The extent of change in pH during
experiment,
 The pH of milk in first day is 6.75. In
contrast, the pH of milk in fourth day is
4.8. So, the change in pH is = 6.75 – 4.8 =
1.95

18. Application of acidity in milk

19.  Many of the cheese are produced in
food industry. Cheese can be produced
by using milk and soy milk

20.  How curd or cheese can be produced by
own at home or in kitchen?
 Explain.

21. Yogurt is one of the Malaysian’s choices.
Yogurts come from milk that may help
prevent from Osteoporosis.

23.  A milk+ vinegar/ lemon juice + heat
 A milk + acid (produced by bacteria) +
heat
 A milk + rennet + heat
 Milk fat & protein separate from the
liquid
 cheese

24.  Need acidifiers to convert
Milk sugar lactic acid
 Acidifiers = lemon juice / bacterial
special starter cultures purchased from
a cheese-making suppliers.
 Bacteria are added to acidify the milk.
 So, rennet will work.

25.  Milk is fermented + lactose-loving
bacteria = yogurt.
 The lactose-loving bacteria consume
lactose - produce lactic acid
 Lactic acid  responsible for tart
flavor + thickening (acting on the casein
protein in the milk.)

26.  Different compositions lactic-acid
bacteria = vary in yogurt-like products.
 US’s yogurt, made with lactobacillus
bulgaricus and streptococcus
thermophilus.
 The milk needs to be fairly warm between
105 and 115 degrees in order to the
organisms in this culture to function.

27. 1. Repeating the experiment using
unpasteurized and Ultra Heat treated
milk,
2. Keeping the container of milk at
different temperature whether in fridge
or an incubator,
3. Using different milk source such as
goat’s milk, cow’s milk and soy milk in
experiment, and
4. Using different milk product such as
Dutch Lady, Marigold, Everyday, Nestle
and Farmhouse Milk (F&N).

28.  Educational data logger motivates
students & increase student’s interest
in learning process.
 In future, data logger can be used in
school in Malaysia and also educational
institutions.
 Make students more familiar with
technology instrument / computer.
 The data that viewable make students
more easily to analyse the data.