The content of ash found in the literature was higher, which is due to the presence of bones and skin in the whole fish sample but not in purified muscle meat. With respect to the FPH, all samples exhibited a similar content of protein, whilst the amount of oil is almost double in horse mackerel samples. The ash content was, in all cases, higher compared to the fresh muscle, this may be due to the increase of salts in the media caused by the addition of 1 M sodium hydroxide solution during hydrolysis.