Protein-phospholipid assembly governs the delivery and digestion of bioactives in natural and reconstituted flaxseed oil bodies

The interface formed by biomolecular assemblies is crucial for the stability and functionality of emulsions. Oil body (OB), natural organelles with a triglyceride core surrounded by protein-phospholipid monolayer, represent ideal biomacromolecular complexes. However, how their unique protein-phospholipid interactions determine functional advantages over artificial emulsions remains unclear. This study analyzed the interfacial components of flaxseed oil body. Based on this, the FOB group (contained OB and carotenoids loaded OB) was selected as the experimental group, while the EO group (contained artificial emulsion and carotenoids loaded artificial emulsion) with similar composition ratios to OB was constructed as the control. Unlike the random arrangement of components in artificial emulsions, membrane proteins in OB were anchored via a central hairpin domain that penetrated the phospholipid alkyl chains, with their hydrophilic ends interact with the lipid headgroups. This well-ordered interface endowed the FOB group with superior stability during storage and digestion, thereby improving the utilization of sensitive loads (carotenoids and α-Linolenic acid) by 1.3-fold compared to the EO group. Interestingly, this structure also helped maintain oil droplet sphericity in the intestine, facilitating interfacial lipolysis and thus increasing free fatty acid release to 1.37 times that of EO group. Additionally, carotenoids transmembrane loading into OB induced interfacial loosening, increasing the lipolysis rate while slightly compromising stability. In contrast, pre-dissolved carotenoids did not alter the interface of artificial emulsion, leaving its delivery behavior unchanged. These findings clarify the key advantages of the OB interface, offering clear guidance for developing better delivery systems by learning from natural design.