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Nutritional Status, Characterization and Fatty Acid Composition of Oil and Lecithin Isolated from Fresh Water Fish Shoul (channa Striata)

Md. Rasel Molla
Department of Biochemistry and Molecular Biology, Rajshahi University, Rajshahi, Bangladesh

A. K. M. Asaduzzaman
Department of Biochemistry and Molecular Biology, Rajshahi University, Rajshahi, Bangladesh

Md. Abdur Rashid Mia
Department of Biochemistry and Molecular Biology, Rajshahi University, Rajshahi, Bangladesh

Meftah Uddin
Department of Biochemistry and Molecular Biology, Rajshahi University, Rajshahi, Bangladesh

Shahangir Biswas
Department of Biochemistry and Molecular Biology, Rajshahi University, Rajshahi, Bangladesh

Md. Salim Uddin
Department of Biochemistry and Molecular Biology, Rajshahi University, Rajshahi, Bangladesh

Abstract/ Executive Summary:

Fishes are rich sources of different types of nutrients. Some species are found in marine water; on the other hand some varieties are available in fresh water. Consumption of fish is very beneficial to the health and development of the human body and fish becomes an integral part of the food culture of populations in many countries. They provide essential nutrients to the human. The aim of this study was to estimate the nutritional status of the selected fish species, to extract and characterize the fish oil and lecithin. Fish oil contains higher amount of polyunsaturated fatty acids which have significant effect in maintaining a healthy cardiac life. Biochemical composition of shoul (Channa striata) was determined. It was found that fishes are rich sources of protein and other nutrients. All the other parameters such as, moisture, protein, lipid, total sugar and ash were found in significant amount in shoul. Shoul fish oil was extracted using n-hexane by soxhlet apparatus. The percentage of oil from shoul fish powder was 12.64 (g% w/w). Lecithin was also extracted from this fish fleshes before and after oil extraction. Lecithin was 2.07 (g% w/w) and 3.10 (g% w/w) before and after oil extraction. It was found that percentage of lecithin was increased after oil extraction. The physicochemical properties of fish oil and lecithin were investigated. The higher saponification value and iodine value indicates that oil and lecithin contains shorter fatty acid chain length with lower molecular weight and the presence of higher amounts of unsaturated fatty acids in the samples. Low acid value and peroxide value indicate higher quality index of fish oil and lecithin. The oxidative stability of shoul fish lecithin was also measured by thiocyanate (TC) method and thiobarbituric acid (TBA) method. Shoul fish lecithin showed higher oxidative stability due to the presence of natural antioxidant. Fatty acid composition of shoul fish oil and lecithin was measured by gas chromatography (GC). The important polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were found to be 0.49% and 1.37% in fish oil. But lecithin contains only 7.8% DHA and other monounsaturated fatty acids. This fish oil and lecithin also contain higher amount of monounsaturated fatty acid and average amount of polyunsaturated fatty acids. Fish oil and lecithin also act as sources of essential fatty acid. Therefore, we can use this fish oil and lecithin in edible purpose, food industry and pharmaceutical industry.

Keywords: Fish Oil, Lecithin, Fatty Acid Compositions, Oxidative Stability, Shoul

Location: Department of Biochemistry and Molecular Biology, Rajshahi University, Rajshahi

Start Date:

End Date:

Program Area: Quality and Nutrition

Commodity: Fish

Objectives:

The aim of the study was to estimate the nutritional status of the selected fish species, to extract and characterize the fish oil and lecithin.

Methodology:

Materials: The fresh shoul fish were collected from local market of Rajshahi, Bangladesh. Sample Preparation: The fish fleshes were separated from bone and were sundried for about 72 hours. The sun-dried fleshes were then grinded by mechanical grinder and stored at - 20°C until further analysis. Then, oil was extracted from both fishes by Soxhlet extraction apparatus using n-hexane and stored at 4°C for further analysis. Lecithin’s were extracted from fish powder following standard method. Extraction of Oil from Shoul Fish: The extraction of oil was carried out in a Soxhlet apparatus using n-hexane as solvent. Oil, triglyceride portion of shoul fishes was extracted by suitable solvents under the operating condition. Continuous Soxhlet extraction apparatus was used for the extraction of oil. About 60-70 gm of sun dried powder from shoul fishes was placed into the extraction thimble and the extraction was run about 5-6 hours until the colour of the condensed solvent at the top of the apparatus was clear. The solvent was evaporated at low temperature (almost ambient temperature) and the fish oil was stored at 4°C temperature. Isolation of Lecithin: Lecithin’s were extracted from stored fish powder and Soxhlet extracted residues according to the method of Palacios and Wang modified by Uddin. In briefly, 100 ml of ethanol (95%) was added to 30 g of fish powder residues and stirred for almost 12 hours by a magnetic stirrer. The mixture was then centrifuged at 6000 rpm for 10 min. The supernatant that contained mainly polar lipids with very low amounts of neutral lipids was collected in a separatory funnel. The precipitate of residue was further extracted with 100 ml of ethanol (95%) and followed centrifugation, the supernatant was added to the previous ethanol extract. Twice volume of hexane was added to the ethanol extract for separating the neutral lipids from the polar lipids. The ethanol phase was then collected and evaporated at 40°C. The remaining lipid residue was dissolved in hexane. A fifth volume of chilled acetone (4°C) to hexane was added to the hexane mixture with slow stirring for precipitation of the gummy material. The mixture was placed in an ice bath for 15 min and then centrifuged at 5000 rpm for 10 min. The collected precipitate called fish lecithin was stored at - 20°C until further analysis. Characterization of Fish Oil and Lecithin: The iodine value of oil and lecithin was measured by the method of Hanus. The iodine value of fat or oil is the amount of halogen absorbed under specific conditions and is expressed as the number of grams of iodine per 100 grams of fat or oil. Saponification value was measured by IUPAC. The saponification value of the fat or oil is the number of milligrams of potassium hydroxide required to saponify completely 1 g of fat or oil. The saponification value is related to the molecular weight of fat or oil and therefore provides information on the mean molecular weight of the combined fatty acids. The acid value was measured according to the official method of IUPAC. The acid value was the amount of milligrams of KOH required to neutralize the acids present in 1 g of sample. Peroxide value was determined by the method of AOCS. The peroxide value is defined as the milliequivalent of peroxide oxygen combined in a kilogram of oil. Determination of Fatty Acid Composition by Gas Chromatography (GC): GC analysis was performed to determine the fatty acid compositions of oil and lecithin from shoul fish. A Hewlett Packard gas chromatograph (6890 Series II GC system) with a fused silica capillary column (100 m length x 0.25 mm internal diameter, 0.2 μm of film, Supelco, Bellefonte, Pennsylvania, USA) was used. The fatty acid methyl esters were firstly prepared according to the AOCS official method of Ce 2-66 (AOCS). Nitrogen was used as the carrier gas (1 mL/min) of the fatty acid methyl esters. The oven temperature was programmed according to Uddin. The initial temperature, 130°C was constant for 3 min and then increased to 240°C at a rate of 4°C/min followed by a hold at 240°C for 10 min. Temperature both for injector and detector were 250°C. Fatty acid methyl esters were identified by comparison of retention time and standard fatty acid methyl esters mixtures (Supelco, Pennsylvania, USA). Oxidative Stability of Fish Lecithin: To measure the oxidative stability, emulsions of lecithin in water were oxidized at 37°C. Three emulsions of lecithin in water (w/w) (linoleic acid 4%, lecithin 1%, water 95%; lecithin 5%, water 95%; β-carotene 1%, lecithin 4%, water 95%) were prepared. Deionized and degassed water were used for emulsion preparation. The mixture was properly homogenized by a homogenizer. The oxidative stability of fish lecithin was measured by using linoleic acid and β- carotene as standard. Oxidative stabilities were checked by the thiocyanate (TC) and thiobarbituric acid (TBA) methods, which were used to measure the antioxidant activity. In this study, these two methods were performed to measure the quality of the extracted lecithin in terms of its oxidative stability. Thiocyanate Method (TC Method): The oxidative stability of fish lecithin was measured by using the method of Mitsuda. The peroxide formed by lipid peroxidation reacted with ferrous chloride and formed ferric ions. Ferric ions then combined with ammonium thiocyanate and produced ferric thiocyanate. In briefly, 0.1 ml of emulsion solution was added to 4.7 ml of 75% ethanol and 0.1 ml of 30% ammonium thiocyanate. Then 0.1 ml of 0.02 M ferrous chloride in 3.5% HCl was added to the reaction mixture. Exactly, 3 min after addition, the absorbance of a red color was measured at 500 nm. The absorbance was recorded at 120 hours’ intervals during the incubation. Thiobarbituric Acid Method (TBA Method): The oxidative stability of fish lecithin was measured by using the method of Ottolenghi. The extent of lipid peroxidation was evaluated by TBA method. Malonadehyde, the product of lipid breakdown caused by oxidative stress, binds with TBA to form a red complex of thiobarbituric acid reactive substance (TBARS). In briefly, 2 ml of 20% trichloroacetic acid and 2 ml of 0.67% 2-thiobarbituric acid were added to 1 ml of emulsion solution. The mixture was heated at 100°C for 10 min in a boiling water bath. After cooling, the mixture was centrifuged at 3000 rpm for 20 min. Absorbance of the supernatant containing TBARS was measured at 532 nm.

Source of Information: International Journal of Nutrition and Food Sciences 2016; 5(1): 9-15; ISSN: 2327-2694 (Print); ISSN: 2327-2716 (Online)

Article Link (Online Journal): http://www.sciencepublishinggroup.com/j/ijnfs; doi: 10.11648/j.ijnfs.20160501.12

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

It can be concluded that shoul fish oil has the potential to be used as a local source of PUFA due to its comparatively high content of EPA and DHA. Lecithin can be used in pharmaceutical industry, cosmetic industry and also used as food additives and emulsifier.

Knowledge Management: Journal