Orthogonal array design (L9 (34)) was applied to optimize the flaxseed oil (FO) recovery, β- and γ-tocopherols yields and total oxidation value (totox value) using ultrasound-assisted extraction (UAE). The optimized results were then compared with the one extracted by Soxhlet extraction (S.E.) at 8 h. The results revealed that 80.05% FO can be recovered by extraction for 30 min, 30°C and 10:1 solvent/solid ratio by UAE compared to 100% recovery obtained by 8 h, 60°C and 20:1 solvent/liquid ratio by S.E. (taken as reference and standard extraction). β- and γ-tocopherols yield was 40.39 mg/100 g oil at 30 min, 20°C and 10:1 solvent/liquid ratio by UAE compared to 56.37 mg/100 g oil by S.E. Totox value of FO by UAE was lower compared to S.E., which is a promising results for better quality and further processing of the oil. No significant differences were shown between the two extraction methods for fatty acids (p < 0.025). UAE is capable of reducing the financial cost of flaxseed oil extraction, saving time, energy and is also environmentally friendly since very little solvent is used compared to S.E.
Practical applications: Flaxseed oil is an unstable vegetable oil due to its high content of polyunsaturated fatty acids (PUFA), which are mainly composed of alpha linolenic acid (ALA). One effective way to ensure a high quality and low oxidation levels of lipids and lipid containing products is to use efficient and rapid method for the extraction.
(1) Flaxseed oil extraction by UAE and S.E. techniques. (2) Comparison of two extraction techniques on fatty acids modification, FO recovery, β- and γ-tocopherols and Totox value (in relation with extraction time, temperature, and liquid/solid ratio).