A nondestructive method for estimating freshness of freshwater fish

The traditional indictors of fish freshness including total aerobic count (TAC), K value, total volatile basic nitrogen (TVB-N), and sensory assessment (SA) were measured regularly to analyze the freshness changes during chill storage. Electric conduction property of whole fish was also studied by measuring their impedances under different frequencies as a fast nondestructive method. The relationship between traditional freshness indictors and electric conductivity was analyzed to determine the feasibility of evaluating fish freshness based on impedance change ratio (Q value) during storage. The results showed that traditional freshness indictors (TAC, K value, and TVB-N) values increased as storage time prolonged, while Q value and SA decreased. There were good relationships between Q value and TAC, K value, TVB-N, and SA (P < 0.01), with the correlation coefficients were 0.943, 0.996, 0.951, and 0.968, respectively. Thus, Q value can be used as a valid index for freshness evaluation and this method via measuring the electric conductivity property of whole fish is a fast nondestructive method for determining the freshness of fish during storage.