AN ALTERNATIVE TO THE GUGGENHEIM, ANDERSON AND DE BOER MODEL FOR THE MATHEMATICAL-DESCRIPTION OF MOISTURE SORPTION ISOTHERMS OF FOODS

The fitting abilities of an isotherm equation originally developed by Ferro Fontan et al. (J. Food Sci., 47, 1590-4, 1982) (FF) was compared with the well-known GAB model. For this purpose literature data of 15 6 food isotherms (comprising 92 different food products) were examined with both models. The results of the evaluation indicated that the FF equation is an accurate tool for the mathematical description of food isotherms. The FF equation represents accurately the sorption isother m of 92 different food products (proteins, starchy, cereals and oilsee ds, meats, vegetables, miscellaneous) in the range of water activity 0 .10-0.90 with only 2-4% average error in the predicted moisture conten t. In fact, the average error for the 156 isotherms examined was only 3.3%. The FF equation only has three parameters that need determining (as has the GAB model); thus it is proposed as an alternative equation to the widely used GAB model.