Oil-assisted extraction of polyphenols from press cake to enhance oxidative stability of flaxseed oil

Cold-pressed flaxseed oil is rich in omega-3 fatty acids but also highly vulnerable to lipid oxidation. Polyphenols might improve the oxidative stability of oils. As common pressing processes are not sufficient to transfer polyphenols from seeds to oil, a customized screw extruder was developed. In addition, an oil-assisted extraction of polyphenols from press cake was applied. The effects of an open process were compared with a nitrogen-flushed and sealed process regarding polyphenols, peroxides and tocopherols in oil. Most polyphenols (492 ± 49.6 mg GAE/100 g seed) remained in the cake and only a small amount was transferred into the oil (0.27 ± 0.11 mg GAE/100 g seed) in the open process. To enhance the polyphenolic content in flaxseed oil, an optimized method using oil as an extraction solvent for polyphenols from press cake was developed by considering press cake/oil ratio, number of extractions and extraction time. Results showed that a threefold extraction for 30 min and a press cake/oil ratio of 1:2 led to a 12-fold increase (1109%) of the polyphenol concentration in the oil whereby resistance to lipid oxidation increased by 38%. The results represent a cost-effective method to enhance the oxidative stability of cold pressed oils.