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.

Practical Application

Barley pearling flour can be a good source of a natural mixture of the family of vitamin E components, tocopherols and tocotrienols, which have been shown to have health benefits. Hulless barley varieties have higher lipid contents and are richer in tocols. Supercritical CO2 can be used to extract barley lipids.