Numerical model for the combined simulation of heat transfer and enzyme inactivation kinetics in cylindrical vegetables

In order to elucidate the effect of a heat treatment on the activity of oxi dative enzymes, heat transfer in stems of broccoli florets was studied. A c onductive heat transfer model with convective boundary conditions was devel oped and solved using the finite element method. The thermophysical propert ies of broccoli (Brassica oleracea L. Italica) were estimated by means of f itting the model predictions to the temperature recordings at a specific lo cation in the broccoli stem. The computed parameters were used to generate an overall predictive heat transfer model for a variety of heat treatments where the temperature and time intervals can be changed randomly. A kinetic model of enzyme inactivation was linked to the overall heat transfer model . The temperature-time profiles during a number of heating and cooling proc esses were evaluated for the effect of the thermal process on the peroxidas e activity. As an application the lipoxygenase inactivation in asparagus (A sparagus officinalis L.) was also estimated. (C) 2000 Elsevier Science Ltd. All rights reserved.