Plant sterol precipitation in system composed by fatty acids using in-situ synthesized ionic liquids

•Plant sterols can be precipitated from fatty acid based ionic liquids.•Over 80% of plant sterols recovery and over 90% purity can be obtained.•Plant sterol precipitation is only slightly affected by the fatty acid used.•Plant sterol precipitation is strongly inhibited by other molecules.•Recovery of 79.4% and purity of 991% plant sterols are reached from tall oil. Plant sterols and stanols are bio-derived compounds used in functional foods because of their hypocholesterolemic effect. Currently, plant sterols and stanols are recovered from tall oil and vegetable oil waste streams by using high vacuum distillation and crystallization. The aim of this work was to explore the recovery and purification of plant sterols and stanols using ionic liquids. Particularly, in-situ protic ionic liquids were synthesized by mixing an amine and fatty/resin acids as a model system of tall oil and vegetable oil waste streams, then an anti-solvent precipitation was performed using alcohols and water. Precipitation temperature, alcohol concentration, water concentration, type of alcohol (methanol and ethanol) and structure of amine (triethylamine, butylamine, and methyldiethanolamine) strongly affect the precipitation from model systems. On the other hand, precipitation time (3–12 h) and type of fatty/resin acid (myristic acid, oleic acid, abietic acid) only slightly influence the precipitation. Results show that when myristic acid was used, the best combination of recovery and purity is reached using triethylamine and methanol with maximum experimental values of 79.9 % of purity and 99.4 % of recovery at 5 °C, 120 % alcohol, 30 % water, and 12 h. Unfortunately, the precipitation performance of plant sterols and stanols from tall oil (5.3 %) using triethylamine and methanol is significantly worse than the performance observed in model systems, achieving maximum experimental values of 70.5 % of recovery of and 76.5 % of purity. However, it was found that saponifying the tall oil before the precipitation significantly improve plant sterols and stanols recovery and purity.