Modeling Aspects in Simulation of Mef Processing of Solid Behaving Foods

Abstract

Moderate Electric Field (MEF) processes involve electric fields less than or equal to 1000 V/cm (Sastry, 2008) and found applications in food heating processes. Industrially, systems based on MEF at 50 Hz (traditionally addressed as ohmic) are employed for heating of liquid food products (sauces, fruit juices) or particulate-dispersed-in-liquid food products (soups). Solid-behaving heterogeneous systems have been less studied, especially due to the not easy coupling between the physical and electrical characteristics of the materials that constitute the food system subjected to MEF assisted heating.The set-up of a virtual lab able to simulate the MEF assisted heating of a heterogeneous food system allows to investigate on the role played by main process parameters (applied electrical potential, MEF cell geometry and electrode configuration) as well as on materials’ electrical conductivity and thermos-physical properties, and also on geometric characteristic of the food system itself. On the other hand, the set-up of such virtual tool is not trivial because it requires the coupling of phenomena of different nature (the passage of electric current in the MEF circuit, including the food loading system; the heat transfer within the food system and its coupling with the local gradient of the electrical potential). In this work, the modeling aspects related to the simulation of MEF processing applied to a heterogeneous food system are presented. Particularly, the study was devoted to analyzing the MEF heating performances in a food system made by 3 meatballs dispersed in 145 g of reconstituted potatoes. The food system was put in a experimental MEF cell 100 mm long, 51 mm wide, with electrodes made in stainless steel. The model set-up has been built following the work presented by Marra et al. (2009). Comparison of experimental results with heating trends provided by simulations in different operating conditions (applied potential gradient of 3 and 4 V/cm) have shown a good agreement when dissipative effects were considered on applied potential. Discrepancies may be due to electrolysis happening near the electrodes.