Effects of three different stunning/slaughtering methods on physical, chemical, and sensory changes in rainbow trout (Oncorhynchus mykiss).

BACKGROUND: Electrical stunning (E) and asphyxia in the air (A) are two common stunning/killing methods for fish. However, they can stress the fish and affect flesh quality, so an alternative should be found. The present study aimed to evaluate the effects of carbon monoxide asphyxia (CO) compared to E and A on the evolution of post rigor mortis changes in rainbow trout (Oncorhynchus mykiss) fillets related to chemical, textural, and sensorial properties during storage time. RESULTS: Fish fillets from the E group showed a higher pH (P < 0.05) than the A ones, both at time of rigor resolution (TRR 0) and from TRR 4 until TRR 7 (7 days after rigor resolution, which corresponded to 10 days post mortem), with the CO group being always intermediate. The CO treatment ensured that the fillets showed the lowest yellowness index (b*), even if only at TRR 2 and TRR 5. Lipid oxidation and texture profile analyses were unaffected. Sensory analysis revealed that the CO fillets had the lowest odor intensity and the highest juiciness scores (P < 0.05). The sensory descriptors resulted the most discriminant variables of the fillets obtained from the differently stunned animals, as resulted by the canonical discriminant analysis. CONCLUSION: The carbon monoxide stunning/slaughtering method could be applied to rainbow trout without detrimental effects on physical, chemical, or sensory characteristics of the fish flesh. © 2018 Society of Chemical Industry.

Carbon monoxide as stunning/killing method on farmed Atlantic salmon (Salmo salar): effects on lipid and cholesterol oxidation.

BACKGROUND: Carbon monoxide (CO) has been recently utilized as a new stunning/killing procedure for Atlantic salmon (Salmo salar). Its effects on lipid and cholesterol oxidation of farmed Atlantic salmon fillets were evaluated at two times of refrigerated (2.5 °C) storage, T0 (64 h after death) and T14 (14 days from T0). The use of CO was compared with the commonly utilized percussion (P) method. RESULTS: Fatty acid profile, primary (conjugated dienes) and secondary (TBARS) oxidation products, cholesterol oxidation products (COPs) and carotenoids were unaffected by the killing method. Despite the low oxidative status of lipid (0.66 and 0.60 mg malondialdehyde kg(-1) muscle in P and CO fish respectively), cholesterol was found to be highly oxidized (0.17 and 0.13 mg COPs kg(-1) ). Storage significantly affected oxidative stability of fish muscle by increasing oxidation products. Interestingly, TBARS content doubled while the increase for COPs was not homogeneous: α- and ß-epoxycholesterol increased by 25%, whereas triol and 7-ketocholesterol increased by 48 and 62% respectively. CONCLUSION: The quality of salmon fillets just after slaughtering and after 14 days of refrigerated storage at 2.5 °C did not change, irrespective of the killing method adopted, suggesting that the CO method may be applied without any detrimental effect on the quality of fish fillets. © 2015 Society of Chemical Industry.

Carbon monoxide stunning of Atlantic salmon (Salmo salar L.) modifies rigor mortis and sensory traits as revealed by NIRS and other instruments.

BACKGROUND: Methods of stunning used in salmon slaughter are still the subject of research. Fish quality can be influenced by pre-, ante- and post-mortem conditions, including handling before slaughter, slaughter methods and storage conditions. Carbon monoxide (CO) is known to improve colour stability in red muscle and to reduce microbial growth and lipid oxidation in live fish exposed to CO. Quality differences in Atlantic salmon, Salmo salar L., stunned by CO or percussion, were evaluated and compared by different techniques [near infrared reflectance spectroscopy (NIRS), electronic nose (EN), electronic tongue (ET)] and sensory analysis. RESULTS: Thawed samples, freeze-dried preparates and NIRS devices proved to be the most efficient combinations for discriminating the treatments applied to salmon, i.e. first the stunning methods adopted, then the back-prediction of the maximum time to reach rigor mortis and finally to correlate some sensory attributes. A trained panel found significant differences between control and CO-stunned salmon: reduced tactile crumbliness, reduced odour and aroma intensities, and reduced tenderness of CO-treated fillets. CO stunning reduced radiation absorbance in spectra of thawed and freeze-dried fillets, but not fillet samples stored in ethanol, where it may have interacted with myoglobin and myosin. CONCLUSIONS: The good results in a rapid discrimination of thawed samples detected by NIRS suggest suitable applications in the fish industry. CO treatment could mitigate sensory perception, but consumer tests are needed to confirm our findings. © 2015 Society of Chemical Industry.