Revisiting nutritional assets of blue-backed fish from the North Adriatic sea: a valuable source of minerals besides a wealth of n-3 LC-HUFAs?

Blue-backed fish is a collective term quite loosely used to designate pelagic finfish species of small or medium-to-small size, Atlantic mackerel and Atlantic herring probably being the best-known of the whole lot. Basically in all the so-called health beneficial “Mediterranean diets”, the word “fish” is evocative of this group of rather oily and savory fish, since they figure among the natural foods best endowed in n-3 LC-PUFA. This nutritional feature seems to be their overriding one, up to the point that their use as potentially good sources of macro and micro minerals could go overlooked. To make a contribution towards redressing this situation, two popular blue-backed fish (European anchovy or Engraulis encrasicolus, EE; European pilchard or Sardina pilchardus, SP), and four less renowned species (European sprat or Sprattus sprattus, SS; round sardinella or Sardinella aurita, SA; garpike or Belone belone, BB; Atlantic horse mackerel or Trachurus trachurus, TT) were sampled over eighth months (Fall through Spring) from wholesale fish markets based in and in the vicinity of Cesenatico (Romagna coast, Italy). Controlateral fish fillets were analyzed by ICP-AES before and after oven baking (OB) up to 70°C core temperature for five macro (Ca, Mg, Na, K, P) and five micro (Fe, Zn, Cu, Mn, Se) elements in order to obtain their true retention values (TRV), up to now lacking in the literature. Clupeids (SA, SP and SS) emerged as the best endowed with the selected macro and micro minerals, SP proving to be the richest in Mn and Se among them. As to the remaining species, BB revealed a surprisingly high Fe content, comparable to the highest levels found in Clupeids. Upon cooking, the highest yield (%) was for BB (87.8), the lowest for EE (65.0), the other species staying in between. In general OB induced an increase in the macro and micro mineral contents of the flesh, although this variation proved to be statistically significant solely for EE and, within this species, for six out the ten selected elements, which should be ascribed to its rather large cooking losses. TRV differed among the species for P (EE and BB with the maximum, M, and SP with the minimum, m), Fe (M for TT, m for SA), Zn (M for SP, m for TT), Se (M for EE and TT, m for SS), in any case with values revealing a modest level of leaching, if any. As to their potential to satisfy human daily requirements (adult male), with reference to the 2006 edition of the Dietary Reference Intakes (U.S. Institute of Medicine of the National Academies, Washington, DC) and the threshold definitions provided by the U.S. National Institutes of Health (Bethesda, MD), the cooked flesh from Clupeids proved to be a “good source” (10-19% of the Daily Value, DV) for Mg, Fe and Cu, while revealing themselves to be “high” (> 20% DV) in P, Zn and, above all, Se.