Utilizing Impedance for Quality Assessment of European Squid (Loligo Vulgaris) during Chilled Storage

This study evaluates the quality of chilled squid Loligo vulgaris by non-destructive measurements of bioelectrical impedance from the first post-mortem day under controlled conditions. Squid samples were stored at 4.5 °C and 55% of relative humidity for 11 days. Impedance magnitude (|Z|) and phase (φ) at 200 frequencies (100Hz to 100MHz) were measured using an Agilent 4294A Precision Impedance Analyzer with needle-type multi-electrode array on days 1, 2, 3, 4, 5, 8, 9, 10, and 11 of storage. The changes in color, sensory properties, total volatile nitrogen, pH, and water holding capacity were also determined. The obtained results indicated that the samples could be classified into five to six distinctive groups by measuring the electrical parameters at frequencies close to 5MHz. In general, φ is less dependent on temperature and measurement setup than |Z|, while records at 5MHz correlate well with the days of storage (R2 = 0.968). The data imply that it is only possible to estimate the length of storage for the samples with measurements of phase angle, which can be useful for the development of new analytical instruments. Biosensors have a practical industrial application, as it is demonstrated that bioelectrical impedance data correlates well with the days of chilled storage.