Mineral and trace element composition of the roe and muscle tissue of farmed rainbow trout (Oncorhynchus mykiss) with respect to nutrient requirements: Elements in rainbow trout products

BackgroundDue to excellent nutritional properties of fish and fish products, dietitians recommend their larger share in the diet, for both the prevention and treatment of diet-related diseases. In this context particular attention should be given to fish eggs (roe). The aim of the study was to compare the content of selected minerals and trace elements in the roe and muscle tissue of aquaculture-reared rainbow trout. Moreover, the extent to which an edible portion of 100 g of fish product (roe or fillet) satisfies the requirements for these elements in adult consumers (women and men) and children was determined.MethodsThe research material was represented by 20 farmed rainbow trout females (Oncorhynchus mykiss). In muscle tissue and roe the proximate composition, energy value, and nutritional quality index were examined. Concentrations of K, Na, Ca, Mg, Zn, Fe, Mn and Cu were determined by flame atomic absorption spectrometry analysis. The levels of minerals and trace elements in fish products were used to calculate the percentages of the recommended dietary reference values for adults and children in portion of 100 g.ResultsThe roe had higher content of 7 elements including, Zn (29.40 ± 1.38, 27.74–30.91 mg/kg), Mn (1.66 ± 0.08, 1.55–1.73 mg/kg), Fe (11.17 ± 0.35, 10.75–11.60 mg/kg), Cu (1.24 ± 0.04, 1.21–1.30 mg/kg), Ca (546.90 ± 23.68, 522.02–578.96 mg/kg), Mg (546.97 ± 23.68, 522.02–578.96 mg/kg), Na (403.61 ± 5.53, 397.29–407.57 mg/kg) compared to muscle tissue, respectively, Zn (2.73 ± 0.97, 0.94–3.77 mg/kg, Mn (0.22 ± 0.10, 0.14–0.46 mg/kg), Fe (2.19 ± 1.44, 1.02–5.50 mg/kg), Cu (0.24 ± 0.06, 0.17–0.36 mg/kg), Ca (164.07 ± 71.72, 93.24–306.32 mg/kg), Mg (240.00 ± 73.37, 127.92–316.41 mg/kg), Na (273.37 ± 99.65, 183.93–524.41 mg/kg). In turn, the muscle tissue contained 3 times as much K (5159.87 ± 974.70, 4004.63–6343.91 mg/kg) as the roe (1713.65 ± 58.68, 1643.97–1764.14 mg/kg). The roe covered the recommended nutrition standards (population reference intake, PRI and adequate intake, AI) to a greater extent than the fillet for all analysed trace elements and minerals except K. For children, the contribution of roe to the reference intake of such elements as Mg, Zn, Fe, Mn and Cu was particularly high. Therefore the roe should be considered as a source of Mg for all consumer groups, and as high in Zn for women and children. The suggested portion of fillet and roe provided only 2–3 % of the daily requirement for Na.ConclusionsDespite the differences found, both roe and fillet from rainbow trout are a good source of analysed elements. The results indicate the need to continue research in order to determine the influence of other factors on the content of minerals and trace elements in roe and the possibility of using gonads to enrich other food products with elements.