Thermal Preservation

1
Thermal Preservation

• Cold Processing

2
Thermal Preservation- Cold Processing

• Chemical reactions involving enzymes or microbes
  are usually the cause of food spoilage.
• The speed at which chemical reactions occur are
  directly related to the temperature of the food.
• The chemical reaction rates roughly double for
  every 10 C. (18F) increase in temperature.

3
Types of Cold Processing

• Refrigeration
• Temperature should be kept below 4C (40F).
• Slows the growth of bacteria it does not stop
  it.
• Once food reaches room temperature, bacteria will
  start to grow again, increasing the rate of
  spoilage.

4
Freezing

• Temperature should be 18C (0F) or lower.
• Food will keep for several months in a frozen
  state.
• Freezing may change the texture of some foods.
  (When the water in the food expands, the ice
  crystals may cause the cells to rupture).

5
Freezer Burn

• Foods should be stored in airtight packaging to
  avoid freezer burn.
• If the packaging is not airtight, moisture will
  evaporate from the food.
• Evaporated moisture will re-freeze on the
  packaging or the walls of the freezer.
• The food cannot regain the lost moisture, thus
  becoming tough and dry.