VCE FOOD TECHNOLOGY
Unit 3 outcome 1
Primary and secondary processing of dairy products
Most of the food that we eat today has undergone some form of processing. There are two types of
processing that food may be subject to.
Primary processing
This is the initial stage of processing that a food undergoes after harvest. The food retains its
essential qualities. Foods may undergo primary processing to make them safer to eat, easier to
transport, more appealing to consumers or more convenient to use. Examples of primary processing
are the milling of wheat and rice, refining of sugar, extraction of corn kernels from the cob and
pasteurisation and homogenisation of milk.
There is also subcategory of primary processing:
Post harvest treatment
This is merely preparing food for sale after harvest or slaughter. Post harvest treatments do not alter
the physical appearance of the food significantly. It literally allows the food to be saleable and ready
to undertake further preparation. Examples include waxing apples, removing the feathers from a
chicken and washing and grading eggs.
Secondary processing
Secondary processing of food occurs after primary processing to create food products that are
significantly different from the original raw ingredients that form the product. It subjects the food to
processes such as heating, mechanical force and the additional of chemicals and flavourings. During
Food and Technology classes, much of the practical work undertaken could be seen as secondary
processing. Examples include cooking fried rice from Jasmine rice, muffins from flour and yoghurt,
cheese, custard or ice cream from dairy products.
VCE FOOD TECHNOLOGY
Unit 3 outcome 1
The table below describes the stages in the primary processing of whole milk. Fill in the table with
the relevant information.
Stage
Milking
Description of process
Effect of process

Mechanical milking machines
draw milk from the cow’s udder
using suction cups attached to
the teats
The milk is transported to
stainless steel vats via large
pipes, where it is refrigerated
The milk is then transported from
the farm to the dairy
On arrival at the dairy, the raw
milk is tested to ensure that it is
clean and free of high levels of
harmful bacteria
If it is fit for consumption it
passes through to large storage
tanks

The milk passes through heat
exchange pipes and is heated to
72°C for 15 seconds
It is then rapidly cooled to <4°C

The liquid is forced through tiny
nozzles under pressure
The force causes an increase in
the surface area of the fat
globules and they no longer
clump together



Testing


Pasteurisation


Homogenisation








Packaging and
transport


The pasteurised, homogenised
milk is packaged in sterile plastic
or cardboard containers
The milk is then transported to
wholesale or retail outlets in
refrigerated trucks, where it is
stored at >4°C until sale


The milk is collected from the
cow twice per day
The milk temperature is brought
down from the temperature of
the cow to a safer temperature
outside the Temperature
Danger Zone (TDZ) of around
2°C
Milk is an unstable food and
may contain high levels of
harmful bacteria; these will be
identified during the testing
stage. If levels are too high, it
will be discarded
The low storage temperatures
reduce the rate at which milk
spoils by keeping it outside the
TDZ
Harmful bacteria and food
spoilage enzymes are
deactivated. The milk is now
safer to consume
The flavour of the milk changes
slightly – it takes on a mild
‘cooked’ flavour
The mixture is now a
homogenous mixture – the fat
globules become more stable
and will not consolidate and rise
to the top of the milk as cream
The milk has a creamier mouth
feel and thicker texture than
before homogenisation
The milk is whiter than before
homogenisation
The pasteurised, homogenised
milk is ready for sale through
retail and wholesale outlets
It is now in a safe, convenient
form for use in a variety of
recipes or as a stand-alone
product
VCE FOOD TECHNOLOGY
Unit 3 outcome 1
The table below describes the stages in the secondary processing of whole milk into yoghurt. Fill in
the table with the relevant information.
Stage
Additional protein is
added to milk
Heating of the milk
Description of process
 Extra protein is added to the milk
 This protein is in the form of
casein, the natural thing for in

protein found in milk
 The milk is cooked for 30 minutes 
at 85°C or at 90°C for 10 minutes
Live bacterial cultures
introduced

Milk held at 40°C


Flavouring, packaging
and transport
Effect of process
 The protein content of the milk
becomes higher





This allows yoghurt to set to a
firm consistency
The protein is denatured and the
end product has better
consistency
Once the milk has been heated, it  The quantity of ‘good’ bacteria
is cooled to the desired
is significantly increased
temperature and live bacterial
cultures are introduced
The milk is held at a stable
 The lactic acid produced during
temperature of 40°C for 2-3
fermentation creates a sour
hours or at 30°C for 18 hours.
taste and acidic pH levels in the
Fermentation occurs during the
yoghurt.
stage.
 The milk solidifies into curd.
This causes the protein strands in
When the curd is distributed
the milk to mesh together and
(e.g. by placing a spoon in the
the milk becomes solid
yoghurt) the whey may seep
out of the product and separate
The yoghurt is cooled rapidly to
 The yoghurt is transformed with
stop any bacteria multiplying
a variety of textures, flavours
and colours
Additives such as colouring,
thickening or preserving agents
 The market share of the
may be introduced. Other
manufacturer may be increased
ingredients may be added such
due to a wider range of products
as sugar fruit puree or fruit
available
pieces, cereals and nuts
The yoghurt is then placed into
sterilised containers and sealed
It is stored at a temperature of
<4°C
The yoghurt is then transported
to wholesale or retail outlets,
where it is stored until sold