Physical and oxidative stability of lipid droplets (oleosomes) in seeds and emulsions

Abstract

Plants have developed a natural solution to a challenge that has long occupied emulsion scientists: how to stably maintain lipids in an aqueous environment while preventing physical and oxidative degradation. Lipid droplets (LDs) are abundant in oilseeds, containing the triacylglycerols (vegetable oils). The physical stability of LDs is ensured by their interface that prevents coalescence, and together with surrounding molecules, protects against oxidation. Despite these advantageous properties of LDs as a whole, industrial vegetable oil extraction often involves the use of organic solvents that dissolve the apolar triacylglycerols, discarding the natural protective mechanism of the LD interfacial molecules. Understanding the structure-function role of the LD interface is essential for inspiring the industrial design of stable emulsions. Our review offers insights into the mechanisms underlying the exceptional stability of LDs in seeds, and after their extraction to create aqueous LD dispersions. We emphasize the key role of the interfacial layer in maintaining their physical stability, in particular through the formation of a dense, elastic network by oleosins, the most abundant proteins on the LD interface. Additionally, we highlight the multi-layered antioxidant system developed by seeds to protect LDs from oxidation, comprising both intrinsic (tocopherols) and extrinsic (phenolics and storage proteins) components.