Effect of Roasting on Bioactive and Antinutritional Components of Flaxseed (Linum Usitatissimum)

Flaxseed (Linum usitatissimum) collected from Morang district, Nepal was studied to explore the effect of roasting at 180oC for 5, 10, 15 and 20 min and soaking (12 h followed by sun drying followed by roasting at 180oC for 15 minutes) on its bioactive compounds (flavonoids, polyphenol and anti-oxidant activity), nutritional and anti-nutritional compounds (hydrocyanic acid and oxalate). The crude extracts of samples were prepared using 80% methanol by maceration technique for analysis of total flavonoid content, polyphenol content and free radical scavenging activity. Roasting of flaxseed had significant impact on its bioactive, nutritional and anti-nutritional components. Flavonoid content increased significantly (p<0.001) from 45.33 ± 5.03 mg QE/100 g to 238.16 ± 8.8 mg QE/100 g on roasting whereas there was no significant increment of flavonoid on soaking. Polyphenols content decreased significantly (p<0.001) on roasting and soaking followed by roasting. The highest amount of antioxidant activity was found to be in raw and 15 min roasting i.e 1.57 mg AAE/mg DM. And antioxidant activity was further increased on soaking followed by roasting. Hydrocyanic acid on raw sample was 649.3 ± 1.41 mg/kg decreased significantly (p<0.001) to 115.2 ± 10.41 mg/kg at 15 min roasting. Similarly, oxalate content decreased significantly (p<0.001) on roasting. Soaking followed by roasting further decreased HCN and oxalate content significantly (p<0.001). Protein, fat and fiber content were decreased significantly whereas calcium content increased significantly on 15min roasting. Similarly, on soaking followed by roasting, protein, fat and calcium content were decreased and crude fiber increased significantly.