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
Before After 1 day
What happen to the milk? Why?
Planning and Doing Experiment – observation of
the change in pH when the milk is left for 1 day.
1. Did you see a reduction of pH shortly after
starting the experiment?
2. What causes the reduction in the pH of
3. Does the speed of change in pH stay
constant over the whole experiment
4. Calculate the extent of change in pH
obtained in the process.
5. What would be the results of incubating
UHT milk over the same time period?
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?
By using data
logger, we do not
need a constant
The graph can
The result can be analyzed
and interpreted easily.
Easy to perform.
Measuring the pH of Milk. Retrieved on 31st
August 2010 from