Freezing and ice crystals formed in a cylindrical food model: part I. Freezing at atmospheric pressure

Cylindrical gelatin gels were frozen at atmospheric pressure with different operating conditions (air-blast freezing at different air temperatures and brine freezing). A method to calculate a local freezing rate was proposed to take into account the variation of freezing rate as a function of the radius. A linear evolution of the local freezing rate according to the radius was observed whatever the freezing process was. Frozen gels were freeze-dried and sliced perpendicularly to the heat flux. The ice crystal marks were measured according to the radial position with image analysis software. Each radial distribution of ice crystal size was characterised by the mean representative diameter. A linear regression permitted to link the ice crystal mean representative diameter to the radial position. On addition, the variation in the mean diameter with the local freezing rate was fitted by a power law. (C) 2000 Elsevier Science Ltd. All rights reserved.