Quantification of dry matter % and liquid leakage in Atlantic cod (Gadus morhua) using computerised X-ray tomography (CT)

Farmed Atlantic cod (Gadus morhua L) were subjected to computerised X-ray tomography (CT) to evaluate CT as a non-destructive and rapid method for analysing muscle dry matter percentage (DM%) and liquid leakage in cod fillets. The study consisted of a total of 317 Atlantic cod (three batches) with gutted weights varying from 0.7 to 2.7 kg. The fish were scanned at four anatomical defined positions in the longitudinal direction. DM% in whole fillets correlated positively with average CT values over all scan positions, demonstrating that CT can be used as a non-destructive method to predict dry matter percentage in cod (r = 0.6 to 0.9; SEP = 0.3 to 0.7 DM%). The scan position anterior to the hind back fin gave highest prediction accuracy (r = 0.63 to 0.93), and DM% in whole fillets provided better information than DM% analysed in specific anatomic positions. CT value and DM% increased from head to tail in all three batches (P < 0.001), demonstrating that the CT-method can provide information also about the variation of DM% within fillets. Classification of liquid leakage during storage into low (< 6%), medium (6–10%) and high (> 10%) amounts also corresponded significantly with distinct CT (HU) intervals, demonstrating the potential for studying and improving liquid holding capacity in cod fillets using CT. Significant differences were detected in CT and DM% between sexes and between families (P < 0.001) indicating genetic variation in these traits and a potential for improvement by selective breeding.