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Keywords:

  • Cheese analogues;
  • cheese microstructure;
  • emulsification;
  • extrusion cooking;
  • processed cheese;
  • protein gelation

Summary

Processed cheese was prepared batchwise and by extrusion cooking. The cheddar-based cheese mix contained varying amounts of polyphosphate ions, rework, lipids, water and/or non cheese proteins. The extrusion conditions (barrel temperatures, screw speed and screw profile) were also varied. The texture, structure and colour characteristics of batch and extrusion-processed cheeses were evaluated using penetrometry, scanning electron microscopy and reflectance measurements. The degree of fat emulsification was assessed and the proportion of casein nitrogen sedimentable by ultracentrifugation was determined, as a means of following micellar disruption plus casein restructuring due to extrusion and to the additional creaming step. Results indicate that extrusion cooking can be used to continuously mix, melt, emulsify and gel the cheese mix constituents, and that processed cheeses or cheese analogues of varying texture (spreadable to sliceable) can be obtained, with a mean residence time in the extruder of about 100 seconds.