BODY-COMPOSITION AND SENSORY ASSESSMENT OF 3 WEIGHT GROUPS OF ATLANTIC HALIBUT (HIPPOGLOSSUS-HIPPOGLOSSUS) FED 3 PELLET SIZES AND 3 DIETARY-FAT LEVELS

In the present investigation, we tested the effects of varying initial fish weight (0.8 to 1.8 kg), pellet size (12-27 mm Phi), dietary fat level (10-39% of dry matter) and their cross-terms upon the fat conten t in a standardized fillet cut of farmed Atlantic halibut (1.3-2.7 kg) after 6 months. A factorial design (FD, 2(3)) plus four centre points was applied. The fish were individually tagged and reared at a mean t emperature of 8.2 degrees C, Lipid content in the fillet was modelled with the aid of PLS (partial least squares) regression on size and sex subgroups. A sensory panel consisting of 11 trained assessors tested the effects of final fish weight and dietary fat contents on multiple sensory parameters. These data were analysed by ANOVA and principal co mponent analysis (PCA). Wide intra-and interindividual variation in fa t content were observed. A standard Atlantic halibut fillet quality cu t (A) is suggested for future work on fillet quality, together with me asurements of fat along the dorsal and the ventral fin base. The PLS m odels of lipid deposition in the fillets showed a positive influence f rom increased initial fish weight and increased dietary fat content. P ellet size showed a minor positive contribution to the fat deposition in the fillet. The sensory test showed that larger halibut (2.1-2.7 kg ) fed diets containing 20 or 39% fat were characterized by a fresher a cid more acidic flavour and a more juicy consistency, compared to smal ler fish (1.4 kg), irrespective of the small fish groups' dietary regi me. The smaller fish were characterized by rancid flavour and off-flav our. In addition to the sensory data, the evaluation of the feed from a feed production viewpoint showed that it is more economical to utili ze herring filleting offal to produce a high fat feed (39%) that ensur es the same fillet quality in the Atlantic halibut as the medium fat f eed does. We, thus, conclude that the fat content in the feed for Atla ntic halibut should be optimized at a level near 40% in due time befor e the slaughtering period, and that the fish preferably should pass 2. 0 kg before being slaughtered. (C) 1998 Elsevier Science B.V.