Transcript High temperature methods

High temperature methods
Pasteurisation and UHT
 During pasteurisation liquid is heated and held at a high
temperature for a short time.
 Pasteurisation is mainly used to process milk, fruit juices and
other liquids.
 Different liquids are heated to different temperatures for
different amounts of time.
 Milk is usually heated to 72C for 15 seconds and then cooled
rapidly to below 10C which extends the shelf life by days. But
only kills some bacteria.
 During UHT liquid is heated to a very high temperature for a
short time . Milk is heated to 133C for 1 second and this extends
the shelf life by months. There is no change to the flavour and
kills of all the bacteria.
Sterilisation
 During sterilisation food is
heated to high
temperatures for longer
than pasteurisation or
UHT.
 When sterilising milk is
heated to 110C and held for
30 minutes, which extends
the shelf life by months. In
milk the flavour is changed
because of caramelisation
of the milk sugar lactose.
Most bacteria are
destroyed.
Canning
 Canning is a form of
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sterilisation. Food can be
packed in cans or bottles and
then sterilised.
Sterilised and then packed
into sterile containers.
The advantages of canning
are that food
Has a very long shelf life
Can be kept at ambient room
temperature.
Once the can is opened it
should be treated like fresh
food.