processing_freezing_and_hardeninig

PROCESSING METHODS:

FREEZING AND HARDENING

Yoghurt types

Individual processes

Legislation

Energy requirements

Suppliers

Other sites

 

Freezing involves exposing the food product to sub-zero temperatures to cause the solidification of the water fraction in the product



© 1999
Helene Coetzee

Yoghurt can be frozen in a

  • continuous ice cream freezer, with capacities of 100 to 3 800 litres/hour
    • chilled when compressed air is incorporated into the product while it is continuously being frozen to -6°C
    • chilled to freeze some of the water while the mixture is agitated by the scrapers blades and beaters of the freezer
    • residence time of the ice cream in the freezer is 30s
    • rapid rate of freezing results in small ice crystals forming
    • OVER RUN/increase in volume may be between 100-180%.

    Continuous freezer

 

(Graphics courtesy of Tetra Pak)

Figure: A continuous freezer

  • batch freezers
    • is a refrigerated cylinder fitted with scraper blades
    • mixture is cooled to -6°C
    • revolving beater incorporates air into the mixture - this results in an increase in volume (OVER RUN) which may be between 80-100%