Development of a new method for fast measurement of water sorption isotherms in the high humidity range - Validation on gelatine gel

A fast and accurate method has been set up to measure sorption isotherms of solid foods in the water activity range 0.9-1. In a purpose-built device thin slices of the studied material are submitted to an air flow of very high velocity (more than 10 m s(-1)), at any temperature between 4 degrees C and 40 degrees C. Air relative humidity is controlled by a reduction in pressure of a saturated air. This method was validated over the range 0.7-0.9 using gelatine gel samples by comparison with the standard saturated salt method. Results obtained at two temperatures (3.5 degrees C, 20 degrees C) and three values of pH (4, 5.2 and 8) were used to test the ability of different fitting models. (C) 2000 Elsevier Science Ltd. All rights reserved.