Transcript Low temperature methods pages 58-59

Low temperature methods
Bacteria become dormant (don’t
reproduce but are not dead). Bacteria
are not destroyed by low
temperatures and become active
when the food warms up again.
Chilling and cook-chilling
• Chilling is used for foods like
sandwiches and cream cakes.
The food keeps for a short time
and is stored between 1C and
5C. The low temperature slows
down enzyme action and
bacterial growth.
• Cook Chilling is used for ready
meals. Food is cooked and
cooled to 0C to 3C. Products
have a shelf life of five days.
Freezing
• Freezing is used for prepared
dishes, fruit and vegetables. It
can be done commercially or
at home.
• At home frozen foods should
be kept at -18C. Some fruits
and vegetables may need
plunging into boiling water for
a short time before freezing.
This is called blanching.
• Quick freezing reduces the
damage to the cells in the food.
It forms small ice crystals,
which reduces damage to cell
walls.
Chillers and freezers
• To maintain the temperature
of chillers and freezers
• Regularly monitor the
temperature with a probe or by
data logging
• Record the temperature and
store for evidence.
• Use sensors and warning lights
to warn of temperature rise
• Keep the door shut
• Check and maintain the seals
• Defrost regularly
• Do not over fill.
Consumer use
• Most food poisoning is caused
by poor food transportation,
storage and use at home.
Frozen, chilled and cook
chilled foods should be....
• Transported home quickly
• Stored and cooked according
to instructions
• Cook chilled dishes must be
eaten within two hours of
cooking
• Leftovers should not be
reheated
• Frozen foods should not be
refrozen.
Accelerated Freeze Drying
• Accelerated freeze drying is a
combination of freezing and
drying.
• Food is frozen quickly and
then placed in a vacuum under
reduced pressure. It is heated
and the ice changes to vapour,
leaving the food dry.AFD food
is light and easily restored by
adding water.
• There is little change to the
flavour, colour and nutritive
value. The foods can be kept at
room temperature.