Determination of the lipid content of rainbow trout (Oncorhynchus mykiss) filets with the Torry Fish Fat Meter®

A Torry Fish Fat Meter(R) was used to estimate the lipid content in the filets of rainbow trout Oncorhynchus mykiss weighing from 1.5 to 3 kg. The results demonstrate the necessity to carefully wipe the skin of the fish to prevent interferences from the mucus. They also showed the existence of two gradients of lipid deposition in the muscle: anterior-posterior and dorso-ventral. A calibration difference of 1.2% was observed when the values were compared with reference methods. Lipid content was determined by linear regression with a correlation coefficient of 0.58 and a confidence interval of +/- 1.57% (p < 0.05). The evaluation of the mean value of one group of fishes is more accurate than individual measurements but the latter allows the identification of the leanest or most fatty within a group.