processing_cooling

PROCESSING METHODS:

COOLING

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Cooling involves extracting heat from a food product to decrease its temperature, using an appropriate device such as a heat exchanger and medium, eg. water, air or refrigerant.



© 1999
Helene Coetzee

Cooling can be incorporated when
  • pasteurized milk is cooled to 40-45ºC prior to inoculation
  • fermented milk for stirred, drinking, long-life stirred yoghurt is cooled to 15°C
  • the packaged product for set, long-life set yoghurt is cooled to 15ºC in cooling tunnels where water is sprayed over the product or it is placed in refrigerated storage
  • the final product can be kept in storage under controlled conditions at 10-20°C

Cooling methods:

  • small and medium scale processors can pump water into the jacket of the vessel to cool the contents
  • small scale processors can also use cooling drums place in a cold room
  • tubular or plate heat exchangers can be used for large scale producers
  • plate cooler :
    • is compact, simple and easily cleaned
    • consists of series of stainless steel plates mounted vertically supported by cylindrical bars and tightly packed and sealed together
    • the plates have waffle-like indentations which provide a large heat transfer area and a turbulent flow of the liquids
    • a rubber seal between the plates keep them 16-18mm apart to minimise the risk of structural damage to the coagulum
    • liquids leave the plates through holes in the corners of the plates
    • open and blind holes route the liquids to the correct plate processing area
    • chilled water is used to cool the coagulum indirectly
  • tubular cooler:
    • made up of a bundle of tubes enclosed in a container
    • the coagulum passes through the pipes
    • counter-flow of cooling agent passes around them

for a sketch of a tubular cooler click here or