Abstract
Background/Objectives: Oleosomes, plant-derived lipid nanostructures comprising a triacylglycerol core surrounded by a phospholipid monolayer and interfacial proteins, provide sustainable alternatives to synthetic lipid vesicles. This study compares solvent-free aqueous extractions of oleosomes from five nuts (almond, macadamia, walnut, hazelnut, pine) and five seeds (flaxseed, sunflower, hemp, sesame, canola/rapeseed) to understand how botanical origin influences composition and physicochemical behavior.
Methods: Oleosomes were isolated using solvent-free aqueous extraction. Extraction yield, lipid content, protein content, particle size, polydispersity, and zeta potential were determined using standard analytical assays and dynamic light scattering techniques. SDS–PAGE was performed to evaluate interfacial protein profiles and oleosin abundance.
Results: Extraction yields ranged from 8.4% (flaxseed) to 59.5% (walnut). Oleosome diameters spanned 424 nm to 3.9 µm, and all oleosome dispersions exhibited negative zeta potentials (–26 to –57 mV). SDS–PAGE revealed abundant 15–25 kDa oleosins in seed oleosomes but relatively sparse proteins in nut oleosomes. Seed oleosomes were smaller and exhibited stronger electrostatic stabilization, while nut oleosomes formed larger droplets stabilized primarily through steric interactions due to lower oleosin content.
Conclusions: Variation in oleosin abundance and interfacial composition leads to distinct stabilization mechanisms in nut and seed oleosomes. These findings establish a predictive basis for tailoring oleosome size, stability, and functionality, and highlight their potential as natural nanocarriers for food, cosmetic, and pharmaceutical formulations.
Introduction
Oleosomes, also called plant oil bodies, are intracellular lipid storage organelles composed of a hydrophobic triacylglycerol (TAG) core surrounded by a phospholipid monolayer and structural proteins such as oleosin, caleosin, and steroleosin [1]. These proteins impart remarkable stability through steric and electrostatic mechanisms that prevent coalescence and oxidation.
Due to their amphiphilic nature, oleosomes self-stabilize without the need for synthetic surfactants, aligning with sustainable “green” formulation strategies. Compared to conventional lipid nanoparticles such as solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), or emulsions that rely on chemical surfactants, oleosomes offer inherent biocompatibility and solvent-free processing, which is attractive for food, cosmetic, and pharmaceutical applications [1,2,3].
Vegetable oils are long recognized as safe excipients. Sesame, castor, peanut, sunflower, and olive oils are routinely used as vehicles for parenteral, topical, and otic dosage forms [3,4]. Oleosomes encapsulate these same triglycerides within nanostructured droplets stabilized by natural proteins, integrating the safety of edible oils with the structural sophistication of colloidal nanocarriers.
Although oleosomes have been examined primarily in individual seeds, such as rapeseed or soybean [5,6], a systematic comparison of nut- and seed-derived oleosomes under identical aqueous extraction conditions remains limited, particularly regarding their potential use in food emulsions and nutraceutical delivery systems.
Recent advances have expanded oleosome research beyond food science into diverse industrial sectors, including paints, coatings, lubricants, films, gels, inks, waxes, and even road construction materials, where their natural interfacial films support the “green” replacement of synthetic surfactants [2,7].
Multiple studies have demonstrated that oleosomes can encapsulate and stabilize a range of lipophilic nutraceuticals and pharmaceutical bioactives, including cannabidiol, curcumin, and β-carotene, resulting in improved protection, colloidal stability, and delivery compared to bulk oils or simple emulsions [8,9]. In pharmaceutical contexts, oleosomes serve as biocompatible, excipient- and surfactant-free lipid carriers, offering a natural alternative to synthetic lipid nanoparticle systems, such as solid lipid nanoparticles and nanostructured lipid carriers [2,7]. Significantly, interfacial characteristics that govern pharmaceutical performance, including droplet size, surface charge, and interfacial protein composition, vary substantially across botanical sources, particularly between nuts and seeds [10]. Despite this recognized variability, systematic cross-source comparisons of oleosomes extracted under identical, solvent-free conditions remain limited.
This study tests the hypothesis that nut-derived oleosomes, which are richer in lipid and lower in protein, yield higher extraction efficiency and predominantly steric stabilization. In contrast, seed-derived oleosomes, which contain higher protein levels, produce smaller, electrostatically stabilized droplets [1,5,10,11,12]. By analyzing the physicochemical characteristics and protein banding profiles, this work provides an integrated framework for understanding how the botanical origin influences the structure, stability, and functional performance of oleosomes.
Materials
