3. 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
4. Advantage 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
5. 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.
6. 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?
7. 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 compartment
s
8. 2. pH sensor
To measure pH of milk.
Provide automatic data collection.
Can measure pH from range 0 to 14.
3. Milk
9. 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.
12. 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.
13. 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.
14. 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.
15. 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
16. 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
17. 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)
18. 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
20. Many of the cheese are produced in food
industry. Cheese can be produced by using
milk and soy milk
21. How curd or cheese can be produced by own
at home or in kitchen?
Explain.
22. Yogurt is one of the Malaysian’s choices.
Yogurts come from milk that may help prevent
from Osteoporosis.
23.
24. 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
25. 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.
26. 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.)
27. 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.
28. 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).
29. 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.
