As can be easily deduced, fish proteins are molecules characteristic of finnut-aquatic animals that breathe in the liquid through the gills.
Fish are products of fisheries, but the two nouns are not to be confused.
In fact, the second group, in addition to fish, includes molluscs, crustaceans, sea urchins and various derivatives (fish eggs, fish offal, etc.).
Fish proteins are defined as high biological value peptides (VB = 78), as they contain a mapping of essential amino acids (AAE) very similar to that of human proteins.
Nutritional properties of fish
Fish, together with other fishery products, terrestrial meat, offal and eggs, constitutes the 15st of the seven food groups; like the other products mentioned (... but with specificity reserve!), fish provides good amounts of heme or ferrous iron, B vitamins (especially thiamin, niacin, riboflavin and cobalamin) and the aforementioned high value proteins organic (the latter present in portions of 27-3% of the total edible part). Fish also contains cholesterol, saturated fats and essential fats of the omega-XNUMX family (EPA and DHA) but, on the other hand, as it is NOT vegetable, it DOES NOT provide dietary fiber, phytosterols, good part of antioxidants, folic acid and many other vitamins. , such as ascorbic acid. This means that a diet rich in fish is not necessarily balanced and must be completed at least by the presence of fruit and vegetables and cereals.
The proteins of fish are similar, but NOT the same, to those of meat; it is true that the amino acids ("building blocks" of the peptides) are the same, but their organization and concentration are different. To be sure, the proteins of fish are not only different from those of terrestrial animals or eggs or milk, but also have a considerable variance between them! The proteins of sea fish, compared to the proteins of freshwater fish, have a slightly different composition, so much so that, following degeneration (bacterial and / or enzymatic) of the muscle tissue, the meat of sea fish is free ( starting from triethylamine) methylamine (TMAO - which then transforms into dimethylamine, monoethylamine and formaldehyde, giving the typical smell of rotten fish), while the flesh of freshwater fish free (due to the degeneration of lysine) a molecule called piperidine . However, both types of fish subjected to advanced degradation are characterized by the production of sulphidic acid (by splitting the sulphurous bridges of proteins and by bacterial and / or enzymatic demolition of the sulphured AAs themselves) and biogenic amines (histamine, tryptamine, cadaverine , putrescine and tyramine); read the article: "Fresh fish and its conservation".
Ultimately, however, what essentially affects the field of human nutrition is the VB referred to the average of fish proteins; this is equal to 78, which is a score close to the maximum, instead typical of human or egg proteins.
A final small clarification should be made on the structure and function of fish proteins which, from a food point of view, can be more or less digestible. Among the various peptides contained in the meat of fish species, sarcoplasmic ones are scarce, in particular globular proteins (such as globulin), and those of connective tissue (collagen fibers, reticular fibers and elastic fibers). This last group of proteins, which in terrestrial meat maintain compactness even after cooking the food, is responsible for the prolongation of the gastric stay and for this reason reduces the digestibility of the food; the proteins of fish, on the other hand, which contain few of them, are much more digestible than those of meat.
Fish proteins have been, and still are, the subject of numerous studies in the nutritional and medical fields; it seems that the consumption of fish, in particular of its fats and proteins, determines: a reduction in the incidence of overweight and an improvement in metabolic parameters (blood pressure, cholesterolemia, triglyceridemia, systemic inflammation, global cardiovascular risk), all aspects promoting human health.
While lipidemia seems to greatly benefit from the nutritional intake of essential polyunsaturated fatty acids of the omega-3 series, present in fish, fish proteins intervene by reducing systemic inflammation (in particular, C reactive protein) and improving insulin sensitivity. ; both of these characteristics make fish proteins an important protection factor against type 2 diabetes mellitus.
Note: the studies were carried out using cod proteins and further investigations are awaited for the other main species.
That's not all! Other insights have examined further beneficial effects of fish proteins on human metabolism, but this time of the bio-regulatory type; it seems in fact that the administration of blue whiting proteins (Micromesistius poutassou) has a positive effect on the mechanisms of satiety by reducing the introduction of food. This characteristic, observed on the behavior of rats, was then justified by the hormonal analysis of the sample, which demonstrated the ability of fish proteins to stimulate the secretion of gastrointestinal mediators responsible for satiety: cholecystokinin (CCK) and glucagon peptide. 1 (GPL-1). The result is therefore constituted by a physiological improvement in the regulation of body weight.
- In vitro and in vivo evidence for a satiating effect of fish protein hydrolysate obtained from blue whiting (Micromesistiuspoutassou) muscle - Cudennec B, Fouchereau-Peron M, Ferry F, Duclos E, Ravallec R - Journal of Functional Foods – 4:271-277 - 2012
- Dietary cod protein reduces plasma C-reactive protein in insulin-resistant men
and women - Journal of Nutrition - Ouellet V, Weisnagel SJ, Marois J, Bergeron J, Julien P, Gougeon R, Tchernof A, Holub BJ, Jacques H. - 138(12):2386-91 -2008 Dec.