Impact of specific power input and treatment chamber design on product-process-interactions during ohmic baking of wheat bread

Abstract

Ohmic baking presents an innovative alternative to conventional baking processes. To transfer processing concepts into applications, it is crucial to understand the intricate interactions between product and process, that currently remain largely unexplored. Thus, this study delved into the ohmic baking of wheat bread and the effects of specific power input (1, 3 and 5 kW/kg) on temperature distribution, dough expansion and progression of electrical conductivity. Various parallel plate treatment chamber configurations were employed for the ohmic heating of 300 g of wheat bread dough. The use of 5 kW/kg significantly reduced baking times necessary to obtain a defined target temperature level and distribution (up to 84 %) compared to the use of 1 kW/kg, with a minimum heating duration of 50 s and a total energy consumption of 21 Wh. Lower specific power levels ($\le$ 3 kW/kg) revealed benefits in terms of minimized instances of local high current density. A temperature-dependent inverse relation between the dough expansion (up to 2.8-fold) and the decrease in electrical conductivity during heating was observed. The design of the treatment chambers impacted temperature uniformity and the occurrence of over- or underprocessed product sections. Chambers with thin electrodes of low height and extensive surface area exhibited benefits such as enhanced water evaporation and reduced heat loss.