Investigation of the Effect of Dielectric Properties of the Biscuit on RF Power Uniformity using a Finite Element Computer Model

Abstract

Background: Biscuit baking process is a major energy consuming and quality deciding process. In conventional biscuit baking process which rely on conduction, convection, radiation mode of heat transfer a condition called checking arises. Checking arises due to the build-up of stresses in the product being heated. The cause for the stresses is the differential moisture content between the outer surface and the centre bone of the biscuit and causes cracking of biscuit. Radio Frequency (RF) Post Baking is a proven solution to this problem. But the wide scale industrial use of RF post baking of biscuits is limited by energy efficiency and cost of the RF heating system. Energy efficiency can be improved by having better RF power uniformity/heating uniformity in the sample (biscuit) being RF heated. The uniformity of radio frequency power distribution defined by a metric called Power Uniformity Index (PUI) is used to evaluate the efficiency of the radio frequency heating. Methods: A finite element computer model of the RF heating system for post baking biscuits with staggered electrode configuration was developed using comsol multiphysics software. The dielectric properties of biscuit were varied from a scale of 0 till 80 and its effect on the RF power distribution and hence the heating uniformity in radio frequency post baking of was observed. Findings: The simulation results obtained indicate that the dielectric properties of the sample (biscuit) do have significant effect on RF power distribution and hence the heating uniformity when the values of dielectric constant and loss factor are lower than 10. Application: The results obtained give an insight into the effect of dielectric properties of biscuit on the RF power distribution in RF dielectric heating of biscuits.