Evaluation of Fresh Water Fish Freshness Based on Impedance Characteristics

摘要

Impedance characteristics offish during storage are important parameters for non-invasive measurement of fish freshness. An impedance measurement system with four-electrode was constructed based on bio-impedance theory and Lab VIEW. The effect on impedance characteristics of fish crucian tissue by different excitation frequency, measuring direction, measuring position and electrode type were researched. The results indicates that the fish impedance decreases and phase angle increases while the frequency increases, the impedance measured parallel to the side is bigger than the impedance measured vertical to the side. Different measured position results in different impedance; even at the same measuring position, different decay time gets different impedance. The composite electrode, gill offish and the excitation frequency of 591 Hz were suitable for researching on the impedance characteristics of fish due to its stable and accurate test signal. When measured vertical to the side, the gill impedanceis less than 91.91C1 (while measured parallel is 99.61C1), and the gill phase angle is less than 5.06°(while measured parallel is 4.94°), it indicates the spoilage of the fish.