Correlation between impedance and freshness indicators of silver carp (Hypophthalmichthys molitrix) during 0 ℃ storage

We established a rapid method to measure the freshness of fish by investigating the correlation between impedance and freshness indicators of silver carp (Hypophthalmichthys molitrix) and their variation rules during 0 ℃ storage. We determined the freshness indicators (total aerobic account, K value, juice loss, sensory score) and impedance change ratio (Q value) to analyze their correlation. Results reveal that the total aerobic count, K value and juice loss increased while Q value and sensory score decreased with storage time. On the 15^th day, the total aerobic count, K value, juice loss, sensory score and Q value were (6.85±0.07) log cfu·g^-1, (63.97±1.93)%, (6.26±0.01)%, 10.0±1.4 and (22.92±2.60)%, respectively, indicating that the fillets had lost edible value. The correlation coefficient between the Q value and total aerobic count, K value, juice loss, sensory score were 0.972, 0.976, 0.945 and 0.984, respectively (P < 0.01). Therefore, Q value is a fast and nondestructive indicator to estimate the freshness of silver carp fillets during 0 ℃ storage.