Continuous radio-frequency heating of a model viscous solution: Influence of active current, flow rate, and salt content on temperature rise

Piyasena, P. and Dussault, C. 2003. Continuous radio-frequency heating of a model viscous solution: Influence of active current, flow rate, and salt content on temperature rise. Canadian Biosystems Engineering/Le génie des biosystèmes au Canada 45: 3.273.34. Radio frequency can induce molecular friction in food products resulting in an internal heating effect; therefore, better heating of sensitive liquid food products can be obtained. A study was conducted to investigate the influence of active current (275-490 mA), flow rate (12-48 L/h) and salt content (0-0.7%) on the heating of a model viscous 0.27% guar solution in a 1.5 kW radio frequency heater on the temperature rise during continuous heating. The temperature increase ()T) was inversely proportional to the flow rate. A linear relationship was found between the active current and )T. The effect of salt content was not significant within the range tested. Based on the data obtained, an empirical model was developed to predict )T. The radio-frequency heater can provide enough energy to heat the viscous products up to 86°C under tested conditions. The flow in the holding tube was laminar under the tested conditions for 0.27% guar solution. The maximum power efficiency that could be achieved was 39%.