Tocol composition and supercritical carbon dioxide extraction of lipids from barley pearling flour

Samples of whole grain and 35% pearling flour of 20 different barley varieties grown in Alberta were analyzed for their lipid contents. Total lipid contents of whole grains were within 1.9% to 3.0% (w/w), whereas those of the 35% pearling flour were 4.3% to 7.9%. Lipids of 35% pearling flour fraction of Tercel barley were extracted using supercritical carbon dioxide (SC-CO2 ) at different pressures (24, 45, and 58 MPa) and temperatures (40 and 60 °C) for 3 h. Lipid recoveries of 73% to 97% were achieved using SC-CO2 extraction under different operational conditions. Tocol contents and compositions of whole grain, 35% pearling flour, and SC-CO2 extracts were analyzed using HPLC. Tocol content of the whole grain was 53.8 to 124.9 μg/g and that of the pearling flour was 195 to 363 μg/g of flour. The hulless barley varieties were higher in tocols, with waxy, double waxy and Tercel varieties having the highest levels (P < 0.05). The ratios of total tocotrienols to total tocopherols varied within 1.6 to 3.9 range. Tocol concentrations of SC-CO2 extract fractions varied from 1171 to 4391 μg/g extract depending on the operational conditions. Barley oil is a good natural source of different tocol isomers rich in tocotrienols.