Objective: To evaluate in a systematic manner, the fat, protein, caloric, and fatty acids contents of 35 species of fish, seafood and mollusks, usually consumed in Andalucía (Spain).
Materials and methods: 35 different species, representative of those usually consumed in Andalucía in the course of the four seasons of the year, are studied. In all units of the study, in a portion of the muscle tissue, measurements were taken to evaluate the total fat (extraction by the Folch method and by gravimetry), protein concentration (Kjehldal method), total calories (gas chromatography).
Results: A table shows the concentration of fat, protein and different fatty acids found in the studied species. There is a great interspecies variability in the fat concentration and in that of the different fatty acids. In the same way there is a great interspecies seasonal variety for some of those studied. Independently of the season studied, the relative proportion of fatty acids was not independent of the total concentration of fat.
Discussion: From the nutritional, culinary and gastronomic point of view, in the Mediterranean area it is common to classify the fish as "white" (low fat) and "blue" (fat). However, the systematic study of a large number of species shows that the categorization of "white" or "blue" depends on the time of year in which they are captured. For example, in spring the horse-mackerel (Scomber scombrurus), a fish traditionally considered "blue" (fat), has the same fat concentration as the sole (Soles vulgaris), generally considered "white" (low fat). And the hake (Merluccius merluccius), in autumn, has a fat concentration which is greater than that of the carangoid sea-fish (Trachurus trachurus). Even greater differences can be seen if we classify the fish according to their richness in n-3 fatty acids. These differences in the total fat concentration and in the composition of fatty acids, as well as the inter-relations between both, may be important in determining the circumstances for the caloric and nutritional calculation of a diet, and may explain the differences found between the different tables of food composition, as well as the divergent results found in the epidemiological studies on the association between the fish of the diet and the different diseases such as diabetes or ischemic heart disease.