Dependence of impedance measurements on the temperature and type of electrodes during the freezing sea bass fillets

Cilj ovog rada je bio utvrditi ovisnost električnih parametara tkiva fileta brancina ( Dicentrarchus labrax) o promjeni temperature i tipu elektroda.impedancija(| Z|) i fazni kut(φ) su mjereni s dvije vrste elektroda, na dvadeset i sedam frekvencija u rasponu 100 Hz – 1 MHz. Rezultati su ukazali na primjenu elektroda s većim brojem igala jer se njihovom upotrebom pri višim frekvencijama smanjio utjecaj anizotropnosti na vrijednosti faznog kuta. Utjecaj temperature promatran je tijekom ciklusa dvostrukog smrzavanja i odmrzavanja fileta. Električna mjerenja izvršena su igličastim elektrodama spojenim serijski. Dobivene su jednadžbe za svježi, jedan put smrznuti i dva puta smrznuti i odmrznuti uzorak pri frekvencijama od 5 kHz, 50 kHz, 500 kHz i 960 kHz. Utvrđeno je da se vrijednosti faznog kuta nisu mijenjale s promjenom temperature uzorka. Fazni kut se pokazao stabilnijim parametrom za procjenu promjena na smrznutom ribljem tkivu jer ne ovisi o temperaturi, a pri višim frekvencijama i upotrebom pravilne elektrode ne ovisi niti o smjeru mišićnih vlakana.The aim of this study was to determine the dependence of electrical parameters tissue bass fillets (Dicentrarchus labrax L.) on the change of temperature. Impedance (| Z |) and phase angle (φ) were measured with two types of electrodes upon twenty seven frequencies in the range 100 Hz – 1MHz .The results showed that the usage of multi electrode needle type array reduces the influence of anisotropy on the value of the phase angle at higher frequencies. Temperature effect was observed during two cycles of freezing and thawing. Electrical measurements were performed with multi electrode needle type array. The result were equations for chilled, once frozen / thawed and double frozen / thawed samples at frequencies of 5kHz, 50kHz, 500kHz and 960 kHz. It was found that the values of the phase angle did not change with temperature. Phase angle proved to be more stable parameter for the assessment of changes in frozen fish tissue because it does not depend on the temperature, and at higher frequencies and the use of proper electrodes depends neither on the direction of the muscle fiber