The effects of boiling and smoking on the proximate composition and lipids quality of a freshwater fish (Chrysichthys nigrodigitatus) collected from Nkam River in Cameroon were investigated. Fresh fish was filled, boiled or smoked and then, aliquoted for analyses. One portion was dried at 50 °C and ground into flour for the proximate composition determination. The other portion was served for lipids extraction using the Bligh and Dyer method. The extracted oil was characterized physico-chemically using chemical indexes and GC/FID. Moisture, protein, ash and lipid contents of raw fish were 80.67±4.18, 64.42±1.51, 10.90±0.42 and 22.06±5.40 % dm respectively. The changes in dry matter, protein and ash contents were found to be statistically significant (P<0.05) after smoking. The most important mineral of this fish was the Potassium (7017.54-8771.93 mg/kg). Except the calcium and phosphorus contents which decreased with the treatments, the amount of the other detected minerals was significantly increased. It was also found that these technological treatments significantly increased (P<0.05) the free fatty acids and hydroperoxides formation in oil, while it decreased its iodine value. The fatty acid profile of untreated and treated fish revealed her richness in Palmitic (22.91-34.76%), Oleic (12.83-23.55%), Stearic (11.29-14.81%), Linoleic (LA) (ω6) (2.83-6.75%), Arachidonic (ω6) (2.50-6.64%) and Docosahexaenoic (DHA) (ω3) (1.56-12.31%) acids. The ratio PUFA/SFA of raw fish (0.47) was severely reduced by the smoking (0.26) while it increases after boiling (0.61). This fish contain appreciable levels of Omega-6 PUFA, suggesting that it could be used as a source of healthy diet for human beings. These findings may also be beneficial for the fish industry, nutritionists and researchers who were striving to improve the nutritive value, processing and marketing of selected fish species.

BackgroundsOils of fish origin are a very rich source of Omega − 3 and Omega − 6 fatty acids. They have been suggested to provide numerous health benefits for humans involving antimicrobial properties. Chrysichthys nigrodigitatus and Hepsetus odoe are two fishes well known in Cameroon. The chemical composition and the antibacterial activity of these fishes derived oils are unknown. The study was designed to valorise C. nigrodigitatus and H.s odoe oils activity against food poisoning bacteria.MethodsOils were extracted by pressing and maceration methods. Their quality was assessed by analysing quality indexes including peroxides, acid, iodine, anisidine and thiobarbituric acid values. Chemical analysis was established by gas chromatography coupled to flame ionization detector. Antibacterial activity was evaluated by broth microdilution method.ResultsC. nigrodigitatus oil obtained by maceration exhibited highest acid (7.33 ± 0.00 mg KOH/g), anisidine (34.5 ± 1.84) and thiobarbituric acid (7.50 ± 0.30 μmol MDA/Kg) values compared to that obtained by pressing method (9.13 ± 0.64 and 6.72 ± 0.34 μmol MDA/Kg) respectively. H. odoe oil obtained by pressing method showed highest peroxide value (6.22 ± 1.31 meq O2/kg). Oil chemical analysis revealed long chain polyunsaturated fatty acids of the ω-3 family: linolenic acid (C18:3); eicosapentaenoic acid (C20:5) and docosahexaenoic acid (C22:6) and ω-6 family; arachidonic acid (C20:4). In addition, C. nigrodigitatus oil obtained by pressing and maceration methods showed Minimum Inhibitory Concentrations (MIC) values ranging from 32 to 64 mg/ml. H. odoe oil obtained by pressing method revealed MIC values ranging between 8 and 64 mg/ml.ConclusionsC. nigrodigitatus and H. odoe oils have activity against food poisoning bacteria, due to their chemical composition.

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