Physiological stress and meat quality of pacu (Piaractus mesopotamicus) submitted to CO2narcosis, hypothermia and electrical stunning

Abstract

This study aimed to evaluate the effect of CO2 narcosis (CN), hypothermia (HY) and electrical stunning (ES) on the physiological stress and meat quality of chilled pacu. Pacus submitted to ES took approximately 30 s to unconsciousness, while those submitted to HY lost consciousness in 28 min and to CN in 54 min. Higher catalase, lactate dehydrogenase and glutathione reductase activity were observed in ES. HY led to an increase in cortisol levels when compared to ES and CN. Higher ATP levels were found in CN-exposed pacu. There was a decrease in muscle pH (no difference between treatments) up to 5 h, with an increase after 7 days of storage. The fillets contracted up to 5 h of storage. The levels of total volatile basic nitrogen increased up to 4 days of storage and were higher in pacus exposed to ES and minors in those undergoing HY. The fish fillets subjected to ES were darker, redder and less yellow. Therefore, CO2 narcosis causes less stress and hypothermia improves the meat quality of chilled pacu when compared to electric stunning, therefore, stunning methods recommended for pacu.