Ice nucleation active bacteria were tested as ice nucleator in place of the seeding step currently used in freeze-concentration processes. Pseudomonas syringae prepared by freeze-drying appeared more efficient than silver iodide in reducing the degree of supercooling. Freezing operations carried out on distilled water and 10% sucrose solutions showed that the degree of supercooling (AT) was 3 degreesC with silver iodide, and reached 1.9 degreesC when P. syringae were added. During freeze-concentration assays, the addition of P. syringae led to a lower saccharose level in the crystals, while the cells mainly accumulated with the saccharose in the concentrated phase. (C) 2003 Elsevier Ltd. All rights reserved.