Thermal Image Processing Technique for Determination of Temperature Distributions of Minced Beef Thawed by Ohmic and Conventional Methods

In the present study, the effectiveness of ohmic thawing (OT) on temperature distribution (TD) was evaluated by using a non-destructive measurement method: thermal imaging (TI). The effects of both OT process parameters and sample properties on TD of thawed minced beef were determined. Thermal images were taken from the central cross-sectional area of a thawed sample. In the first part of the study, the effects of OT system parameters (voltage gradient; 10–13–16 V/cm and electrode type; E1:titanium foil electrode with a smooth surface, E2: needled-type titanium electrode, E3: titanium electrode with pyramid surface shaped) and sample shape (X: 13 × 4 × 3 cm3; Y: 13 × 6 × 2 cm3; Z: 13 cm height × 3.91 cm diameter) were analyzed in detail. The best thawing condition (electrode type E2 and sample shape Y) was determined by taking into account of thawing time and TD properties obtained from a developed TI processing technique. In the second part of the study, the effects of OT process on TD properties of minced beef having different fat contents (2–10–18%) were compared with those of two different conventional thawing processes (stationary cold ambient + 4 °C -RT and under cold running water + 4 °C -WT). The percentage of thawed portions in central section was above 68% for OT and varied between 12 and 54% for CT. Rectangular-shaped samples had more homogeneous temperature distributions than cylindrical samples (p < 0.05). TI could be used to control the process by non-destructive monitoring of temperature during OT.