THERMODYNAMIC APPROACH TO EQUILIBRIUM ISOTHERMS IN SALTED STRUCTURED FOOD

Abstract

ABSTRACT Some foods are preserved by salting in NaCl saturation conditions (fish, meat and some vegetables). It is known that the polyphasic and multicomponent character of foods plays a basic role in defining equilibrium conditions; therefore, it is essential for a correct modeling of food behavior. However, in most cases, only one homogeneous phase is considered for process modeling. In this paper, the polyphasic and multicomponent character of foods was applied for thermodynamic description of salted foods in order to have a better analysis of their water sorption isotherms. A simplified model of the food in terms of four phases (aqueous solution of salt and native soluble solids, solid matrix and fat) is proposed. The water sharing out between phases was analyzed, and the water content and relationships for each phase were proposed. This model was applied to salted meat isotherms, obtaining a good fitting between experimental and predicted data. PRACTICAL APPLICATIONSThe final quality of salted meat products depends on the complex cellular structure, salt and water relations and transformations. A new isotherm model for salted products, with structural and thermodynamic considerations, is proposed as a tool to control the production of salted foods.This model describes the structure of food as an insoluble solid matrix with salt and water interactions, liquid phase (water and salt solution) and solid salt, and explains the water and salt distribution during adsorption and desorption of water.Thus, this new model is an excellent tool to predict salt and water interactions in the complex food structure in order to improve some quality parameters of salted products such as content of salt crystals, distribution of salt or protein degradation.