Experimental and theoretical investigation of effects of applications of different types of waves and frequencies on performance characteristics of ohmic thawing process

In this thesis, the investigation of the applicability of ohmic thawing (OT) at the 10 V/cm voltage gradient with different frequencies (5-10-50-100-500-1000 Hz) and wave forms (square and sinus) for thawing of minced beef samples having 10% fat content was aimed. The effects of process application parameters (frequency and wave form) on thawing time, thawing homogeneity, product quality characteristics and performance analysis of system were determined. Optimum ohmic thawing condition having highest product quality and the highest process efficiency was determined. Effects of conventional thawing (CT) and the OT process (for optimum condition) on the product quality, process efficiency, product composition and textural properties have been determined. Also, the OT process was also mathematically modelled, and the compatibility of predictions to the experimental data was investigated. It was determinated that, OT resulted to shorter process times, lower pH changes, higher temperature values, but higher drip loss and more changes in color properties compared to conventional thawing methods (p<0.05). Also, it was determined that OT process at different wave forms had significant effects on the drip loss and process time. Effects of different frequencies on temperature homogeneity and color properties were found. System performance analyses showed that energy/exergy efficiency values of OT method were higher than CT, and that different wave types and frequencies had no effect on the efficiencies. For the voltage gradient of 10 V/cm, optimum ohmic thawing condition was determined as sinus wave from at 1000 Hz frequency thawing conditions.