Analysis of Heat Transfer in Surimi Paste Heated by Conventional and Ohmic Means

Heating of surimi paste was studied to determine the effects of conventional (water-bath) cooking vs. ohmic (electrical resistance) cooking. Results of both experiments and models were observed over the cooking temperature range for Pacific whiting surimi paste having a salt content of 2% and moisture contents of 74% and 80%. A good correlation between model and experiment resulted using a finite element analysis. Ohmic heating under a high voltage gradient (1200 V/m) resulted in a heating rate 11 times higher than that of conventional (90°C water bath) heating for a cylindrical sample of 19 mm diameter. Results also showed the significant effects of the two heating mechanisms upon the time during which the sample center dwells within the critical enzyme activity range. The effects of voltage gradient across the sample, moisture content, heat exchange with the surrounding ambients, and electrode design were also investigated. Heat leakage to the sample holder and surroundings caused a significantly lower heating rate in the outer edges of the sample compared to the center.