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Studies on Nutritional Composition and Characterization of Lipids of Lates Calcarifer (bhetki)

T. Pervin
Department of Applied Chemistry and Chemical Technology, Islamic University, Kushtia, Bangladesh

S. Yeasmin
Department of Applied Chemistry and Chemical Technology, Islamic University, Kushtia, Bangladesh

R. Islam
Department of Applied Chemistry and Chemical Technology, Islamic University, Kushtia, Bangladesh

Kamruzzaman
Department of Applied Nutrition and Food Technology, Islamic University, Kushtia-7003, Bangladesh

A. Rahman
Department of Applied Chemistry and Chemical Technology, Islamic University, Kushtia, Bangladesh

A. Sattar
Department of Applied Chemistry and Chemical Technology, Islamic University, Kushtia, Bangladesh

Abstract/ Executive Summary:

Physico chemical characteristics of lipids extracted from Lates calcarifer and nutritional composition of that fish were analyzed by standard method. The coefficient of viscosity was 447.69 millipoise at 30^oC and specific gravity and refractive index were 0.98 and 1.37 at 30^oC respectively. Saponification value, saponification equivalent, iodine value, peroxide value, acid value, ester value and reichert-meissel value were found 95.50, 286.96, 62.81, 52.59, 1.83, 193.67 and 2.94 respectively. Percentage of free fatty acid, unsaponificable matter and cholesterol were found 0.92, 1.86 and 13.74 respectively. Further, carbohydrate, protein, lipid, moisture, ash and dry matter content of L. calcarifer were found 0.93, 23.5, 5.7, 70, 5 and 30 % respectively. The fish was found to contain 580, 270,140, 120 and 9 mg of Na, K, Ca, Mg and Fe per 100 g respectively. However Cu and Zn were found to present in negligible amount. The fatty acid profiles L. calcarifer were identified by GLC method. Among fatty acid lauric, palmitic, oleic and stearic were found to present 4.49, 52.86, 36.88 and 5.75% respectively.

Keywords: Lates calcarifer; Lipid; Fatty acid composition; GLC; Mineral content

Location: Department of Applied Chemistry and Chemical Technology, Islamic University.

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Marine fish

Objectives:

To study the nutritional composition and characterization of lipids of Lates calcarifer

Methodology:

Sample Collection: About 500 gm of fish (L. calcarifer) were collected from market of Binodpur, Rajshahi, Bangladesh. Prior to analysis, the internal organs were removed and the fish was washed to remove the residual blood. Fish fillet was obtained by cutting the fish lengthwise along the backbone to obtain maximum amount of flesh without including the backbone. The fillet was cut into small pieces. Proximate composition analysis: The moisture, carbohydrate, protein, ash and dry matter contents of the sample were determined by the AOAC methods. The experiments were performed in triplicate and values are expressed as mean ± standard deviation. Mineral Analysis: Minerals analysis of fish sample were done according to the AOAC method, using Atomic Absorption Spectrophotometer. Extraction and estimation of total lipids: Total lipids were extracted from fish muscle tissue samples and estimated. Briefly, a chloroform/methanol solvent mixture (2:1, v/v) was added to samples in the ratio solvent/tissue of 20:1 (v/w). The samples were homogenized three times and each homogenization step was followed by cooling of the sample for 1h at 4°C. The chloroform/methanol extracts were incubated overnight at 4 °C to allow the organic (containing the extract of total lipids) and aqueous layers to separate completely. The upper (aqueous) layer was removed, and the lower (organic) layer was rinsed with chloroform/methanol (2:1 v/v), then placed into a glass tube. The total lipid fraction was obtained by evaporating the lower phase. The solvent was removed in a rotary evaporator under vacuum at 40 °C. These extracts, representing the total lipids, were weighed, and results were noted. The resulting extract of total lipids was stored at 4 °C until further analysis. Characterization of the Lipid: Physical and chemical properties of the lipid extracted from L. calcarifer were determined by standard method. Preparation of the methyl ester: The samples lipids were converted to their constituent fatty acid methyl esters (FAME) according to standard method. 5g lipid was taken in a round bottom flask (125 mL) and saponified with alcoholic potassium hydroxide solution (50 mL). The mixture was then refluxed for 45 minutes on a water bath until it became clear. The reaction mixture was allowed to cool and then neutralized with HCl (5N). Alcohol was removed from the neutralized solution by evaporation over a steam bath. 25mL water was added to this alcohol free solution and pH of the solution was adjusted to 1-2 drops by adding concentrated HCl. The acidified aqueous mixture was then extracted with 20 mL of ether in a separating funnel and the extraction was repeated for three times. The combined ether extract was washed with water in order to remove any adhering HCl. Ether was then removed from the extract to give the fatty acid mixture. The fatty acid mixture was then esterified with methanolic solution of sulfuric acid (0.25M, 5mL/gm acid). After esterification, the mixture was dissolved in ether (25mL) in a separating funnel and was washed with dilute sodium carbonate solution until the effervescence ceased. It was then washed with water, dried over anhydrous sodium sulfate and finally ether was removed to give methyl ester mixture. Gas liquid chromatographic analysis of methyl esters: Analysis of methyl ester was carried out with a "PUE UNICAM" 4500 U model gas chromatograph equipped with a flame ionization detector. A glass coiled column (3mm I.D. 2.1m) packed with 70-100 mesh chromosorb after impregnating it with 10% diethylene glycole succinate was used for the regular packed column GLC. The temperature programming in the oven was from 130°C to 230°C with the rate of rising 4 °C per minute. The oven, injector and detector temperature were 190 °C, 200 °C and 205 °C respectively with a nitrogen carrier gas flow rate 30 mL/minute. The speed of the chromatogram was at 0.5 cm/minute. The fatty acids in the mixture were identified by comparing its relative retention volume. The area of each chromatogram peak was determined by multiply the height of the peak by the width of the peak at one-half of the height.

Source of Information: Bangladesh J. Sci. Ind. Res. 47(4), 393-400, 2012

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It can be concluded that due to the presence of appreciable amount of protein, fat, mineral and fatty acid, this fish and fish products such as fish burger, fish cake and fish crackers and also for use in controlling diet while the wastes recovered can be used for fish meal or silage production for animal feeds. Hence, they are suitable as potential industrial material for possible utilization for different products.

Knowledge Management: Journal