Effects of frequency and temperature on the electrical conductivity of grass carp ( Ctenopharyngodon idella) fillets and skin under ohmic heating

To verify the feasibility of ohmic heating ( OH) as a food thermal processing method for freshwater fish, grass carp, which is one of the four domestic Chinese carps, was used as the object.The impedance of grass carp fillets ( parallel, series) , minced fish and samples with skin were measured with a LCR meter under 50 Hz²0 k Hz after being heated via 50 Hz, 20 V alternating current within a temperature range of 10⁸0 ℃, afterwards the electrical conductivity ( EC) of all the samples were calculated and analyzed.The results showed that all samples displayed a tendency that EC increased with rising temperature and frequency.To fillets samples, due to the existence of membrane and its different direction against the electric current, there was significant difference between EC of parallel and series samples ( p < 0.05) . The EC of minced fish was among the value of parallel and series samples with eliminating the influence of muscle membrane. The sample with skin showed distinct range of EC when compared with other groups of samples, which was influenced by skin, and electrical conductivity was higher when the skin was parallel to the current.