Unlocking flaxseed oleosomes (oil bodies) potential: Optimal extraction and functional insights through enzymolysis or dehulling treatment

Oleosomes are intracellular vesicles within a phospholipid monolayer membrane and have significant potential for use in various food applications as natural emulsions. Flaxseed, an underexplored yet promising crop, shows promise for oleosome utilization. However, the high mucopolysaccharide content in hulls may pose challenges to the extraction efficiency of natural flaxseed oleosomes (N-FOs). In this study, two pretreatment methods were employed prior to aqueous extraction: enzymatic hydrolysis using a cellulase-pectinase-xylanase cocktail and dehulling. Both pretreatment methods significantly improved the extraction yield, with dehulling flaxseed oleosomes (D-FOs) achieving 51.3 % and enzymatically hydrolyzed flaxseed oleosomes (E-FOs) reaching 53.1 %, representing an increase by a factor of five compared to N-FOs. The average droplet size of E-FOs ranged from 1.5 to 1.7 μm across pH 2.0 to pH 10.0, while the absolute value of the zeta-potential for E-FOs at pH 10.0 was the highest at -39.6 mV. Cryo-SEM imaged that E-FOs and N-FOs exhibited a more complete structure than D-FOs, which might be attributed to the increased electrostatic repulsion generated by flaxseed protein and spatial hindrance of incompletely hydrolyzed polysaccharides. LF-NMR spectra showed shorter T₂ values of E-FOBs, confirming increased interactions between residual polysaccharides and oleosomes. The tight and solid-like interfacial film affirmed by the emulsifying activity and rheological results could protect emulsion droplets against flocculation and disproportionation, thus contributing to enhanced emulsification stability. Enzymatic hydrolysis demonstrated a favorable balance between extraction yield and functional properties compared to dehulling or no pretreatment, making it a suitable approach for efficient oleosome extraction from flaxseeds for various plant-based food applications.