Multielemental analysis of raw and cooked flesh from two underutilised fish species.

Objective - To determine macro and micro element contents of the flesh, both raw and cooked, from chub mackerel (Scomber japonicus) and horse mackerel (Trachurus trachurus), two underutilised finfish species frequently caught in the waters of the Gulf of Manfredonia (Apulia, Italy). Methodology- Two batches per species were obtained, dressed, and cooked as described by Testi et al. (same proceedings). After freeze-drying, 0.5 g of each homogenised sample, made up of paired skinned fillets either raw or cooked, were mineralised in duplicate in a microwave system. The macro (sodium, Na; potassium, K; calcium, Ca; magnesium, Mg; phosphorus, P) and micro (iron, Fe; zinc, Zn; copper, Cu; manganese, Mn; selenium, Se) element contents of the samples were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The quality of the analytical results was controlled by repeatedly analysing for relevant elements two certified reference materials, NRCC-DORM2 (dogfish muscle) and BCR-422 (cod muscle), during the 14-month research period. Summary of the main results - The elemental content of the flesh from chub mackerel (CMK) was almost always affected by catch season, the only exception being Mn and Se. Fall CMK flesh was significantly richer in K, Mg, P, Fe, Zn, and Cu. Grilling induced a statistical significant decrease in Na, K, and Mg contents, while having a significant concentration effect upon Zn and Se. CMK cooked flesh, whichever season, was quite a remarkable source of Se, a 100-g serving being able to cover 133% of the requirements of an adult, both sexes. A serving of fall grilled CMK was also an interesting source of P and K (able to cover on average 43 and 10% of an adult daily requirements, both sexes, respectively), and of Zn and Fe (a serving being able to cover 19 and 17% of the requirements of an adult female and male, respectively). Catch season affected significantly the content of several elements in the flesh of horse mackerel (HMK): Na, K, Mg, and Fe levels were higher in wintertime, whereas Mn and Se contents increased in summer. Grilling caused a significant increase in the concentration of Na, K, P, Mg, Fe, Cu, and Se, while Zn and Mn decreased. The grilled flesh from HMK, whichever season, was quite a valuable source of P (a standard serving being able to cover around 37% of the daily requirements of an adult, both sexes) and an interesting source of Zn for adult females (around 10% of their daily needs). Summer cooked HMK flesh could boast so high a Se content that a standard serving would be able to cover 158% of the daily requirements of an adult. The cooked flesh from winter HMK, on the other hand, was both an important Fe source to adult males (22% of daily requirements) and an interesting source of K to both sexes (9% of daily requirements).