Crude protein was measured using the Kjeldahl technique and multiplying N by 6.25. Crude lipid was measured after chloroform–methanol extraction . Samples were homogenized with a high speed homogenizer for 5 min and lipid was
determined gravimetrically after solvent separation and vacuum drying. Gross energy content was measured by combustion in a Parr bomb calorimeter using benzoic acid as the standard. As energy equivalents for protein and lipid, respectively, might be influenced by the method of analysis (protein as N6.25 and lipid by chloroform–methanol extraction), it was decided not to use theoretical values from the literature, but to calculate energy equivalents for protein and lipid directly from the proximate composition of the fish tissue. As energy (kJ), protein (g) and lipid (g) were measured for the same samples the energy equivalents could be derived by using the multiple.
regression: