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

BACKGROUND

Due 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.

METHODS

The 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.

RESULTS

The 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.

CONCLUSIONS

Despite 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.

Protective effects of diet containing rutin against trichlorfon-induced muscle bioenergetics disruption and impairment on fatty acid profile of silver catfish Rhamdia quelen

Trichlorfon is an organophosphate insecticide that is widely used on fish farms to control parasitic infections. It has been detected in freshwater ecosystems as well as in fishery products. There is a growing body of evidence to suggest that certain feed additives may reduce or prevent pesticide-induced toxicity in fish. The aim of the present study was to determine whether acute exposure to trichlorfon would alter bioenergetic homeostasis and alter fatty acid profiles in muscles of silver catfish (Rhamdia quelen). We also sought to determine whether rutin prevents or reduces these effects. Cytosolic and mitochondrial creatine kinase (CK) and activities of complexes II-III and IV in muscle were significantly inhibited by exposure to 11 mg/L trichlorfon for 48 h compared to effects in the unexposed group. Total content of polyunsaturated fatty acids (omega-3 and omega-6) were significantly lower in muscle of silver catfish exposed to 11 mg/L trichlorfon for 48 h than in the unexposed group. Addition of 3 mg rutin/kg feed increased CK activity and prevented inhibition of complex IV activity, as well as preventing all alterations of muscle fatty acid profiles elicited by exposure to trichlorfon. No significant differences were observed between groups with respect to muscle adenylate kinase or pyruvate kinase activities, as well as total content of saturated and monounsaturated fatty acids. Our findings suggest that exposure (48 h) to 11 mg trichlorfon/L water inhibits cytosolic and mitochondrial CK activity in muscle. Trichlorfon also affects activities of complexes II-III and IV in respiratory chain, with important consequences for adenosine triphosphate production. The pesticide alters fatty acid profiles in the fish and endangers human consumers of the product. The most important finding of the present study is that inclusion of rutin improves bioenergetic homeostasis and muscle fatty acid profiles, suggesting that it reduces trichlorfon-induced muscle damage.

Distinct microbial assemblages associated with genetic selection for high- and low- muscle yield in rainbow trout

Background

Fish gut microbial assemblages play a crucial role in the growth rate, metabolism, and immunity of the host. We hypothesized that the gut microbiota of rainbow trout was correlated with breeding program based genetic selection for muscle yield. To test this hypothesis, fecal samples from 19 fish representing an F2 high-muscle genetic line (ARS-FY-H) and 20 fish representing an F1 low-muscle yield genetic line (ARS-FY-L) were chosen for microbiota profiling using the 16S rRNA gene. Significant differences in microbial assemblages between these two genetic lines might represent the effect of host genetic selection in structuring the gut microbiota of the host.

Results

Tukey’s transformed inverse Simpson indices indicated that high muscle yield genetic line (ARS-FY-H) samples have higher microbial diversity compared to those of the low muscle yield genetic line (ARS-FY-L) (LMM, χ2(1) =14.11, p < 0.05). The fecal samples showed statistically distinct structure in microbial assemblages between the genetic lines (F_1,36 = 4.7, p < 0.05, R² = 11.9%). Functional profiling of bacterial operational taxonomic units predicted characteristic functional capabilities of the microbial communities in the high (ARS-FY-H) and low (ARS-FY-L) muscle yield genetic line samples.

Conclusion

The significant differences of the microbial assemblages between high (ARS-FY-H) and low (ARS-FY-L) muscle yield genetic lines indicate a possible effect of genetic selection on the microbial diversity of the host. The functional composition of taxa demonstrates a correlation between bacteria and improving the muscle accretion in the host, probably, by producing various metabolites and enzymes that might aid in digestion. Further research is required to elucidate the mechanisms involved in shaping the microbial community through host genetic selection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-020-07204-7.

Effects of chitosan edible coating containing grape seed extract on the shelf-life of refrigerated rainbow trout fillet

In recent years, use of edible coatings as carriers of food additives and antimicrobial compounds has been considered in fishery products. This study was carried out to evaluate the effects of 2.00% chitosan coating singly and combined with 0.10% grape seed extract (GSE) on microbial (mesophils and psychrophils counts), chemical (thiobarbituric acid; TBA), pH and peroxide value (PV) and sensorial properties of rainbow trout fillet stored at 4 ^°C over a period of 15 days. The coating had a significant effect in reducing aerobic mesophilic and psychrophilic bacteria counts. The TBA, PV and pH of samples of chitosan coating alone and with GSE were lower than control ones indicating a significant influence of coating on fillet shelf-life. Moreover, chitosan coating represented an equal sensorial quality with controls. It can be concluded that chitosan coating containing GSE can help to maintain the sensorial quality and increase the shelf-life of rainbow trout fillets at refrigerated conditions.

Dehydration kinetics of salmon and trout fillets using ultrasonic vacuum drying as a novel technique

In this study, a novel ultrasonic vacuum (USV) drying technique was used to shorten the drying time of fish fillets. For this purpose, ultrasonic treatment and vacuum-drying were simultaneously performed to dehydrate salmon and trout fillets at 55°C, 65°C, and 75°C. In addition, the USV technique was compared with vacuum-drying and oven-drying techniques. The dehydration kinetics of the fillets was successfully described by seven thin-layer drying models with R(2) range between 0.944 and 1.000. Depending on drying temperatures and fish species, the drying times could be shortened using the USV technique between 7.4% and 27.4% compared with vacuum-drying. The highest effective moisture diffusivity was determined in the fillets dried with the USV technique and they increased with increasing drying temperatures. Ultrasonic treatment accelerated the vacuum drying process for the fillets; therefore, this technique could be used to improve the efficiency of vacuum-drying for the fillets.