The application of ultrasound energy to increase lipid extraction throughput of solid matrix samples (flaxseed)

Ultrasound may reduce lipid extraction times and increase analysis throughput of food materials. Ground flaxseed (25 mg aliquots) were extracted in quadruplicate in 2:1 (v:v) chloroform:methanol, 3:2 hexane:isopropanol, 1:1 diethyl:petroleum ether or hexane with exposure to sonication at low frequencies of 20 kHz with a 600 W ultrasonic processor. Power was automatically varied to maintain constant amplitudes of 20%, 60% and 100% of 240 μm for sonication exposures for 5, 10 and 20 min, respectively. Total lipid dry weights and quantitative and qualitative fatty acids were determined. Results were compared to a standard 24-h, Folch-based, 2:1 chloroform:methanol extraction. Longer time exposures and higher sonication amplitudes were associated with increases in lipid recoveries. In particular, ultrasound-assisted extraction in 3:2 hexane:isopropanol for only 10 min resulted in lipid and fatty acid recoveries similar to the 24-h standard method. Comprehensive testing on a variety of sample matrices and food products is required, but lipid extraction by ultrasound has potential to reduce sample processing time.