Radiofrequency Thawing of Frozen Minced Fish Based on the Dielectric Response Mechanism

To preserve the quality of frozen food products, the main goal of suitable thawing is to cause the least amount of damage with the shortest possible thawing time. A radiofrequency (RF) system has potential for use in achieving these goals for industrial thawing operations. This study investigated the characteristics of RF thawing, and sought to determine the optimal conditions for RF thawing by clarifying the temperature distributions in blocks of frozen minced fish. The dielectric properties (DPs) of frozen minced fish and the penetration depths (dp) of thawing were measured under differing methods and conditions. The temperatures measured by the probes were plotted in Surfer and verified by COMSOL simulation. A sharp increase in DPs (e′ and e″) was observed at a frequency of 27.12 MHz (from −3 °C to 0 °C), and a striking dp was found from −15 °C to −5 °C, Electromagnetic waves at this frequency could penetrate our samples easily, and the uniformity of heating was improved at both ranges of temperature. For the size of frozen minced fish blocks that are commonly used in the industry (25 × 15 × 5 cm), the most suitable electrode gap for thawing was found to be 16 cm. Unlike in the results obtained with other thawing methods, the cooked gel properties after RF thawing were unaffected, which proved that the RF system is optimal for use in industrial production.