Proximate Composition, Physicochemical Properties and Antioxidant Activity of Flaxseed

Aims: The aims of this study were to investigate the proximate composition of flaxseed; physiochemical properties and antioxidant activity of flaxseed. Study Design: Using standard analytical methods to determine the proximate composition of flaxseed, extraction of flaxseed in different trials under the same conditions using two different solvents and investigating their physicochemical properties and antioxidant activity. Place and Duration of Study: This study was conducted in the laboratory of department of applied and industrial chemistry, International University of Africa, University of Medical Sciences and Technology and National Centre for Research, Khartoum – Sudan, during June 2019. Methodology: The prepared sample of flaxseeds was tested for proximate composition and then extracted with petroleum ether and n-hexane. The extracted oil was then subjected to physicochemical analysis, GC-MS analysis and antioxidant activity test. Results: The oil yield of flaxseed was high 21.95% and 28.29% with n-hexane and petroleum ether respectively. The results obtained for proximate composition were: moisture (8.50 ± 0.49%), ash (1.96 ± 0.00%), fiber (20.23 ± 3.47%), protein (21.00 ± 0.74%),fat (43.17 ± 0.99%) and carbohydrate (5.14 ± 2.73%).The physicochemical properties of n-hexane and petroleum ether extracted flaxseed oils were: density (0.92 ± 0.00 g/cm3), refractive index (1.47 ± 0.00 and 1.48 ± 0.01 at 28°C), acid value (0.76 ± 0.10 and 0.75 ± 0.20 mg KOH/g), peroxide value (4.67 ± 1.00 and 2.69 ± 0.55 meq O2/kg), saponification value (185.61 ± 0.56 and 187.83 ± 2.08 mg KOH/g oil), unsaponifiable matter (5.57 ± 0.64 and 2.83 ± 0.23 mg KOH/g oil) and iodine value (97.24 ± 0.86 and 97.44 ± 2.93 g/100 g) respectively. Statistical analysis showed no significant difference between the means of the two data sets of physicochemical properties of flaxseed oils extracted with the two solvents used at 95% confidence level. The GC-MS spectrum of flaxseed oil extracted with n-Hexane revealed presence of 27 fatty acids, the predominant were linoleic acid (46.53%), palmitic acid (18.04%), stearic acid (12.23%), linolenic acid (11.63%) and oleic acid (4.24%). While for petroleum ether extract a total of 28 fatty acids were identified the major were: linolenic acid (42.39%), linoleic acid (26.17%), palmitic acid (12.89%), stearic acid (10.73%) and  methyl erucic (1.24%.). The oils also, showed good antioxidant activity in relation to control; 28 ± 0.09 (DPPH) for n-Hexane extract and 26 ± 0.05 (DPPH) for petroleum ether extract. Conclusion: Based on the results obtained flaxseed and flaxseed oil had good potential for human consumption and can be used for other application.