Three commonly available species of marine fishes in Nigeria,
Clupea harengus
,
Scomber scombrus
and
Trachurus trachurus
were subjected to boiling, frying and roasting and their effects on the fishes were observed. Frying reduced the protein content for all the fish types with the effect very pronounced on
Clupea harengus and
Trachurus trachurus but made fish less susceptible to spoilage. Fresh and fried
C. harengus had 62.7 % and 10.6 % protein content respectively, while
T. trachurus had 57.3 % and 9.18 %, respectively. The ash content reduced with all the treatment methods for all the fish species except for boiled
Scomber scombrus. Boiling in water gave fish with the best nutritive value overall.
Scomber scombrus was the most nutritious (in terms of protein and mineral content) of the three and the nutritive value did not diminish with the method of preparation. It is also the most palatable in terms of flavour and texture.
Trachurus trachurus had the least protein value and the protein was very unstable to the treatment methods. The third species,
Clupea harengus is also rich in protein but the protein content reduced with frying. Frying gave a better result when long-time preservation is of interest but boiling was the better processing method when preservation of nutrient is the focus. The results also showed that
Scomber scombrus had the highest oil content (30.30%) followed by
Clupea harengus (12.70%) while
Trachurus trachurus has the lowest oil content (12.25) and irrespective of the processing method, the order remains unchanged. This work also shows that the effect of a treatment type on a fish sample is dependent on the fish species. The oils obtained from the fried fish samples had the least acid values in all cases, while the oils from the roasted samples had the highest saponification values
