Comparative composition and shelf-life of fillets of wild and cultured turbot (Scophthalmus maximus) and Atlantic halibut (Hippoglossus hippoglossus)

Turbot and Atlantic halibut are highly valued fish species. However, very little is known about fillet shelf-life characteristics associated with both species. Thus, fillet α-tocopherol content and proximate composition of wild turbot (1.5 kg) and Atlantic halibut (1.1 kg) caught off the south coast of Ireland and the north-west coast of Iceland, respectively, were investigated. In addition, the susceptibility of fillets, stored under retail conditions, to lipid oxidation and colour change was studied. Proximate composition analysis showed that turbot had significantly higher moisture (P < 0.001) and lower protein (P < 0.001) contents compared to Atlantic halibut. Atlantic halibut incorporated significantly higher (P < 0.001) levels of α-tocopherol into fillets than turbot. Over 14 days of storage on ice, fillets from Atlantic halibut exhibited significantly lower (P = 0.020) levels of lipid oxidation than those of turbot. However, malondialdehyde (MDA) concentrations were generally very low, never exceeding 0.6 μg g^-1 fillet. Turbot maintained a significantly higher (P < 0.001) pH over the storage period. The lightness (L^* values) of fillets from both species increased over 14 days of storage, but was significantly higher (P < 0.001) in Atlantic halibut than in turbot. Turbot developed a relatively intense yellow colour during storage (decrease in hue angle and increase in b^* values), whereas this was not the case for Atlantic halibut. The results of this study demonstrate than fillets of wild Atlantic halibut stored on ice, were less prone to lipid oxidation and discolouration than those of wild turbot. However, quality changes in turbot were very small showing that both fish have tremendous shelf-life capacities in terms of lipid oxidation. These findings are considered in the context of known material for farmed fish.