Advanced food products & process engineering (SAFES) i: Concepts & methodology

Abstract

Food quality and safety are the main concerns of consumers and the principal target of Food Industry processes. The concept of “food process engineering for product quality” has arisen in recent years with the aim of designing and controlling processes to produce food products with very specific properties of quality and safety, previously defined on the basis of market opportunities analysis (ETP, 2006). The final properties of food products are the result of the changes produced in raw materials as a consequence of process treatments (Aguilera and Stanley, 1999). These changes may be observed as differences in quality factors, such as food composition, nutritional facts, taste and flavor, aspect, shape and size, colour, texture, etc. (Aguilera et al., 2003a, b). In the case of colloidal or cellular foods, these changes in food properties may be explained as the result of physical and chemical phenomena produced in line with the process progression such as structure deformations and relaxations (shrinking and swelling), chemical or enzymatic reactions, phase transitions, mass and energy transport phenomena, etc. (Aguilera and Baffico, 1997; Barat et al., 2001). The models currently used in food process engineering usually oversimplify both the food system description and the mechanisms and rate equations of changes. Typically, the food system is supposed to be isotropous, homogeneous and continuous, with only two or three components, distributed in one or two phases (Crank, 1985). In this approach, thermodynamic and kinetic equations deduced for ideal gas or liquids in conditions close to equilibrium are applied to model food with colloidal or cellular structures and, of course, in conditions far away from the equilibrium (Bird et al., 2002). The typical approach used to model food drying operations is a good example of this methodology. Frequently, the models obtained in this way cannot accurately predict the changes in the food properties through the industrial processes when the range of values for the industrial process variables is different from those used in the experiments. In this sense, it is remarkable how scattered reported values in the literature for the experimental effective diffusivities are (Martínez et al., 1998).