The heat sterilizing of a cheese mixture, in preparing cheese-based foods such as processed cheese and cheese spreads, is effected at above 90 DEG C. by passing the mixture continuously through a heat-exchange vessel of the kind in which material coming into contact with a heat-exchange surface is quickly removed therefrom by the action of a moving agitator within the vessel, and homogenizing and cooling the heated mixture, the equipment used for these operations being such as to prevent air reaching the hot mixture, while, at the same time, avoiding a vacuum which would result in loss of volatile ingredients. The vessel may be a cylinder in which is a cylindrical rotor having a helical step, the outer edge of the step passing very near to, but not scraping against, the inner surface of the cylinder as the rotor turns. The mixture may be pre-heated. Heating in the vessel may be above 143 DEG C. for a few seconds. The sterilized mixture may be cooled in a similar vessel. The mixture may be passed through a filter before it is cooled.
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