Effects of different stunning methods on the flesh quality of grass carp (Ctenopharyngodon idellus) fillets stored at 4 °C

The effects of stunning methods (percussion (T1), stunning at −22 °C in a freezer (T2), and immersion in ice slurry (T3)) on the flesh quality of grass carp fillets were evaluated in terms of K-value, total volatile base nitrogen (TVB-N), electrical conductivity (EC), total viable counts (TVC), biogenic amines, and sensory scores during storage. Moreover, fillets were analyzed periodically for pH, hardness, acid phosphatase activity, and the content of glycogen, adenosine triphosphate (ATP), and lactate. Significantly slower ATP depletion, slower reduction in pH, slower lactate formation, and higher initial glycogen level were observed in T3 compared to T1 and T2 (P < 0.05). Grass carp stunned by percussion showed higher TVB-N, EC, TVC, total biogenic amines, and lower sensory scores. Significantly lower TVC (P < 0.05) was exhibited in T3, which indicated that stunning in ice slurry could improve the quality and prolong the shelf life of grass carp.