Differencing sea bass (Dicentrarchus labrax) fillets frozen in different conditions by impedance measurements

Summary The potential of electrical impedance was investigated to differentiate thawed sea bass fillets (Dicentrarchus labrax) previously subjected to different freezing conditions. The HP 4284A Precise LCR meter was used to measure impedance magnitude (|Z|) and phase (ϕ) at 27 frequencies from 0.1 to 1000 kHz. A needle‐type multi electrode array was tested as a probe for impedance measurements. The study showed that fast and non‐invasive control method based on measurement of ϕ on thawed fillets could assess the freezing conditions of white fish at higher frequencies of measurements (500–1000 kHz). The advantages of ϕ when compared with |Z| include its independence on temperature, on puncture depth of the probe and on duration of storage prior to freezing. Usage of a needle‐type multi electrode array reduced the effect of muscle tissue anisotropy; however, even at 1 MHz, the differences in electrical measurements varied around 10–11% depending on muscle fibre direction.