Minimising heat losses during batch ohmic heating of solid food

The influence of cell design on the uniformity of batch ohmic heating of a solid foodstuff was examined. Various ways of minimising heat loss from the cell surface including insulation or providing supplementary heat via a heating belt or panel were assessed but discarded in favour of housing the cell in a hot air cabinet maintained at 80 °C and eliminating the surrounding cell body. Various electrode materials and designs were evaluated prior to opting in favour of platinised titanium electrodes of minimal practicable thickness (1 mm). The final system developed involved the use of a combined ohmic/convection heating with the food stuff contained in a plastic casing pressurised between two spring-loaded electrodes. Under optimised conditions a maximum overall temperature variation of 12.1 °C within the product was achieved after 150 s which was reduced to 8.6 °C after 3 min standing time.