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 oxidative enzymes, heat transfer in stems of broccoli florets was studied. A conductive heat transfer model with convective boundary conditions was developed and solved using the finite element method. The thermophysical properties of broccoli (Brassica oleracea L. Italica) were estimated by means of fitting the model predictions to the temperature recordings at a specific location 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 processes were evaluated for the effect of the thermal process on the peroxidase activity. As an application the lipoxygenase inactivation in asparagus (Asparagus officinalis L.) was also estimated. (C) 2000 Elsevier Science Ltd. All rights reserved.