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Lipid, Fatty Acid and Glyceride Composition of Five Different Varieties of Rice Bran Oil

M. Lutfor Rahman
Natural products Research Division BCSIR Laboratories, Rajshahi-6206, Bangladesh

Md. Jahidul Islam
Natural products Research Division BCSIR Laboratories, Rajshahi-6206, Bangladesh

G.R.M. Astak Mohal Khan
Natural products Research Division BCSIR Laboratories, Rajshahi-6206, Bangladesh

M. K. Hossan
Natural products Research Division BCSIR Laboratories, Rajshahi-6206, Bangladesh

Seatara Khatun
Natural products Research Division BCSIR Laboratories, Rajshahi-6206, Bangladesh

Md. Ibrahim H. Mondal
Dept. of Applied Chemistry & Chemical Engineering, Rajshahi University, Rajshahi-, Bangladesh

Nurul Absar
Dept. of Biochemistry & Biotechnology, University of Science and Technology, Chittagong, Bangladesh

Abstract/ Executive Summary:

Five varieties of rice bran, collected from different automatic rice mills, have been examined for their lipid, fatty acid and glyceride composition. The total lipid contents in different rice bran were found to be in the range of 14.95-16.16%. The total lipid extracts were fractionated into lipid classes by silicic acid column chromatography. The neutral lipid component of the oil varied from 93.76 - 95.08%, diglyceride from 1.51-2.30% and monoglyceride from 1.45-1.69%. The neutral lipid accounted for over 95% of the total lipid present. The analysis of the fatty acid composition, showed 40.18-43.15% oleic acid, 28.45-31.15% linoleic acid, 19.08- 20.86% palmitic acid and 3.13-4.21% stearic acid, as major fatty acids.

Keywords: Rice bran, Rice bran lipid, Triglyceride, Glycolipid and phospholipid

Location: BCSIR Laboratories, Rajshahi

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Rice

Objectives:

1. To examine lipid, fatty acid and glyceride composition of different rice varieties.

Methodology:

Five Varieties (BR-5, BR-10, BRRI-28, BRRI-39 and Kalijira) of rice bran were collected from the auto rice mills of different rice growing area of Bangladesh. The varieties of the bran samples were duly authenticated. The fresh bran samples were taken from the polishers and immediately sieved through 30 mesh sieve for further investigation. The bran samples were extracted with n-hexane in a soxhlet extraction apparatus for eight hours. Lipid was recovered from the solvent by vacuum distillation Lipid thus obtained was purified over a neutral alumina column using pet. ether and diethyl ether (80:20 v/v) as the eluting solvent. Normal TLC, was employed to check the purity of lipid. The free fatty acid (FFA) saponificaiton value, peroxide value and unsaponifiable matters in the oil were determined by the standard methods. Hanus method was followed to determine the iodine value of the oil. Separation of glyceride from rice bran oil - Different varieties of rice bran oil was separated into mano-, di- and trigly- ceride on silicic acid (E. Merck, Darmastadi, Germany, 70-230 mesh) Column. The silicic acid was activated at 120⁰C overnight and again for 1 hour immediately before the column was prepared. Then the silicic acid was hydrated with 5% (w/w) water. A slurry of silicic acid in chloroform was poured into the column (2.5 cm i.d.). 1.5 g oil was dissolved in 15 ml of chloroform and quantitatively transferred to the column. The triglyceride components from different varieties of rice bran samples was eluted with 200 ml of benzene, the diglyceride with 200 ml of a 1:9 (v/v) mixture of diethyl ether and benzene and the monoglyceride with 200 ml diethyl ether. The percent compositions of the glyceride are shown in table 2. The elution was controlled at a flow rate of 1.5-2ml/min. The elution of each fraction was monitored by micro slide thin layer chromatography (TLC) to ensure complete separation of each class of the glycerides during slilicic acid chromatography and the eluted solvents were collected in weighed flasks. The fractions thus obtained were evaporated in a rotary vacuum evaporator and were dried under reduced pressure before being weighed. The purity of the different glyceride components was further checked by TLC using silica gel developed with n-hexane diethyl ether checked by TLC using silica gel developed with n-hexane diethyl ether (80/20 v/v) and identified chromic-sulphuric acid spot tests at 180⁰C. The glyceride was identified by comparison of Rf values with standard references. The weight percentage of each glyceride class was based on total glyceride recovered, which averaged to 96 of the total glyceride present. Fractionation of different rice bran lipid - The extracted rice bran lipid was fractionated into three major lipid groups, neutral lipid, glycolipid and phospholipid by silicic acid chromatography on about 150mg of rice bran lipids. Neutral lipids were eluted with chloroform, glycolipid with acetone and phospholipid with methanol. The elution was controlled at a flow rate of 0.5ml-1.0ml/min. The complete elution of each fraction was monitored by micro slide TLC during silicic acid column chromatography and eluted solvents were collected in weighed vials. The percentages of these fractions were determined by gravimetric method. Separation of saturated and unsaturated fatty acids from different varieties of rice bran oil - Separation of saturated and unsaturated fatty acid were carried out by lead ether method. The oil (50g) was saponified with alcoholic caustic soda to obtain soap solution. A slight excess of lead acetate solution was added to the soap solution to form lead salts of fatty acids which were then separated. Ether was added to the mixture of lead salts the whole mixture was boiled and then cooled at 0⁰C for 24 hours. The precipitated lead salts of saturated fatty acids so formed were separated from the solution of lead salts of unsaturated fatty acids by filtration. The lead salts of unsaturated fatty acids were obtained by removing ether from the ethereal solution. Each group of lead salts was suspended in water and treated with sufficient hydrochloric acid to form fatty acids and lead chlorides. The mixture was then extracted with ether to obtain ethereal solution of each group. On evaporating ether, the fatty acids were obtained in separated group. Finally masses of saturated and unsaturated fatty acids were obtained by weighing them separately. Fatty acid Composition of rice bran oil - Fatty acid composition of rice bran oil was analyzed as their methyl ester, which was prepared by the Boron trifluoride methanol method. A GCD Pye Unicam gas chromatograph equipped with a flame ionization detector was used to determine the fatty acid methyl esters. Nitrogen carrier gas was used at a flow rate of 30ml/min. Fatty acid were separated on a 18X 1/8 I. d glass column packed with 6% BDS (Butanediol Succinate Polyesters) on solid support Anakorm ABS (100/120) mesh. Analysis was carried out at isothermal column temperature 190⁰C, injector and detertor temperatures for all GLC analyses were 230⁰C. Gas chromatographic peaks were identified by comparison with standard methyl ester with respect to retention times against equivalent carbon length (ECL). Peak areas were measured by a Pye Unicam electronic integrator. The percentage of each peak was calculated as the percentage of total area of all the peaks.

Source of Information: BANGLADESH RESEARCH PUBLICATIONS JOURNAL; ISSN: 1998-2003, Volume: 9, Issue: 2, Page: 111-115, November- December, 2013

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The rice bran has been found to contain about 15.11-16.16% oil. From the present data it might be suggested that all the five varieties of rice bran oil are suitable for edible purposes as they contained significant amount of unsaturated fatty acid.

Knowledge Management: Journal