Moisture diffusivity coefficient estimation in solid food by inversion of a numerical model

Abstract

Knowledge of moisture diffusivity coefficients of water in food is a very important physical parameter for design, modelling and simulation of different food plants and related processes such as baking, drying and ripening. Unfortunately specific moisture diffusivity values are not easily found in literature, particularly for processed foods. The aim of this study was to develop a method, based on the inversion of finite element models, to estimate the moisture diffusivity in different solid food products. An example on salami, biscuit and flat bread is shown. The research work was divided in three phases: experimental determination of the moisture concentration versus time in various food products stored in water saturated atmosphere; development of a numerical model of water transfer inside the food product for the numerical determination of moisture content versus time and parameter estimation of moisture diffusivity, by minimizing the distance between numerical model and experimental results using the Levenberg–Marquardt algorithm.The estimated moisture diffusivity coefficients resemble those reported in literature for almost similar products (3.857E−12, 6.804E−11 and 1.792E−12m2/s for salami, biscuits and flat bread respectively). The obtained values were then used for solving direct models, in unsteady conditions, showing a good agreement with experimental data.The method may be used on different food materials and it is possible to hypothesize an integrated automatic instrument, useful both for laboratory and industrial purposes.