Effects of binary organic solvents and heating on lipid removal and the reduction of beany odour in Bambara groundnut (Vigna subterranean) flour

• Beany or grassy odour associated with Bambara groundnut flour was due to lipid oxidation.
• All binary solvents at 60 °C removed lipids and phospholipid effectively.
• Methanol containing solvents could remove phospholipids, and inactivate lipoxygenase and trypsin inhibitors.
• Bambara groundnut flour defatted with chloroform/methanol showed the lowest beany odour.

Effects of various binary organic solvents at different temperatures on the removal of lipids and beany or grassy odour of Bambara groundnut flour were studied. The highest lipid removal was achieved at 60 °C (P < 0.05), regardless of binary organic solvents used. Under the optimal temperature, chloroform/methanol showed the highest lipid removal (87%), followed by hexane/isopropanol (78%). All binary solvents containing methanol had higher efficiency in removal of phospholipids, and inactivation of lipoxygenase and trypsin inhibitors, as compared to isopropanol containing solvents (P < 0.05). Based on FTIR spectra, lipids removed by methanol containing solvents had high content of phospholipids. The flours defatted by methanol containing solvents exhibited the lowest peroxide value, thiobarbituric acid-reactive substances and beany odour intensity than the non-defatted flour and those defatted by isopropanol containing solvents throughout the storage (P < 0.05) of 30 days at refrigerated and room temperatures. In general, chloroform/methanol was the most effective in inactivating lipoxygenase and trypsin inhibitors, retarding lipid oxidation as well as beany odour development in flour. Therefore, chloroform/methanol could be used to lower beany or grassy odour in Bambara groundnut flour.