Freeze concentration is an excellent alternative to evaporation and reverse osmosis for pre-concentration of many liquid foods. However, the build-up of an ice layer on the cooler surface, which is known as ice fouling, is unavoidable even at a low degree of supercooling, e.g. around 0.2 degreesC. This significantly reduces the heat-extraction rate and increases the cost of freeze Concentration. In this study, we found that the onset time of ice fouling on the subcooled metal surface can be indicated by the step increase of the surface temperature due to the release of the latent heat of fusion. We also developed a method to indicate the ice fouling induction time on the cooler surface according to an increase of the AC impedance between the solution and the cooler surface. A mathematical model is presented which correlates the fouling induction time to the degree of supercooling. Factors influencing the ice fouling are studied and discussed in this paper. (C) 2003 Elsevier Science Ltd. All rights reserved.