Salmon muscle microstructure influence on ohmic heating – MRI characterization and computer simulation analysis

This study characterizes the microstructure of salmon muscle, in special the quantity and thickness of the myotomes and myosepta tissues, at five locations (belly, loin, second cut, top loin, and tail) using magnetic resonance imaging (MRI) in order to build simulation models that consider the structure of each tissue to investigate their effect on the electrical behavior during ohmic heating (OH). A block from each location was subjected to OH from 5 °C to 70 °C under an applied voltage of 20 V at 20 kHz in both directions of the electric current (parallel and series) to the muscle arrangement. The OH systems were evaluated experimentally and using three-dimensional computer simulation models. Experimental temperature profiles successfully validated the accuracy of the model results in parallel and series directions at two different locations, showing a low error across all 20 conditions assessed, with 14 conditions exhibiting excellent accuracy (RMSRE <10 %), four conditions showing good accuracy (10 % < RMSRE <20 %), and two conditions presenting fair accuracy (20 % < RMSRE <30 %). Salmon block with thinner tissue (myotomes and myosepta) layers presented a higher heating rate during OH, following the order: tail > top loin > second cut > loin > belly. 3D distributions of current density and temperature during OH were visualized through computer simulations. The results confirmed that the salmon muscle microstructure predominantly influences heat generation distribution according to the current direction. Approaches combining MRI evaluation and mathematical simulation demonstrated their potential to evaluate the OH of food systems of complex microstructures which can be relevant in the design of novel products.