Effects of Boiling and Smoking on the Proximate Composition and Oil Quality of a Commercially Important Freshwater Fish (Chrysichthys nigrodigitatus) from Nkam River in Cameroon

Abstract

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.

Effect of local hot smoking on proximate composition, lipid oxidation, fatty acid profile and minerals content of <I>Chrysichthys nigrodigitatus</I> from Lake Maga in Cameroon

“…Among saturated and monounsaturated fatty acids present in raw fish, the highest was C18:1, followed by C16:1 and C18:0. These observations are different with the findings of Djopnang et al (2018) for the same species. Oleic acid (C18:1) which is very high in C. nigrodigitatus oil has exogenous origin and reflect the type of diet consumed by fish.…”

“…The biochemical composition of raw fish noted in this study are similar to those obtained by others authors for the same species (Tenyang et al, 2016;Djopnang et al, 2018). The moisture content of smoked fish noted in this work is higher than those obtained by Djopnang et al (2018) (15.89%) for smoked Chrysichthys nigrodigitatus collected in Nkam river. Decrease of moisture content occurring during smoking is the consequence of water loss during this process.…”

“…Concerning the oil qualities parameters, the FFA of raw fish oil obtained in this study is very low compared to that obtained by Djopnang et al (2018) with the same species (10.25% oleic acid). The difference could be due to the technique of extraction of lipid.…”

“…The low value of FFA obtained indicates a good quality of this fish product. As shown in Table 2, decrease in IV during smoking process are not in the line with the finding of Djopnang et al (2018) who noted no significant variation between raw and smoked C. nigrodigitatus collected in littoral region. However, these observations are in agreement with the results mentioned by Tenyang et al (2017), who demonstrated that smoking process decrease IV of smoked herring oil.…”

“…Several studies have reported the nutritive value and effect of processing on fish species in some countries. These included: Biochemical composition of some marine fish species of Ghana (Obodai et al, 2009), proximate composition, fatty acid and mineral contents of four freshwater fish from Lake Maga in Far North region of Cameroon (Tenyang et al, 2016), the changes of fatty acid composition in sun dried, oven dried and frozen hake (Merluccius merliccius) and sardinella (Sardinella aurita) (Khaoula et al, 2013), the influence of traditional drying and smoke drying on the quality of three fish species (Tilapia niloticus, Silurus glanis and Aurius parkii) from Lake Lagdo, Cameroon (Ali et al 2011), the influence of smoking method on quality of traditional smoked Bonga shad (Ethnalosa frimbriata) fish from Lagos State, Nigeria (Adeyeye et al, 2015), the effect of boiling and smoking on proximate composition and oil quality of commercially important freshwater fish (Chrysichthys nigrodigitatus) from Nkam River in Littoral Region of Cameroon (Djopnang et al, 2018).…”