Influence of encapsulated functional lipids on crystal structure and chemical stability in solid lipid nanoparticles: Towards bioactive-based design of delivery systems

•Lipophilic bioactive compounds were encapsulated in solid lipid nanoparticles (SLN).•Crystallization behavior of SLN depended on the bioactive and surfactant type.•Oxidative stability of bioactives depended on the crystal structure.•Delivery systems need to be designed specifically for each bioactive compound. We investigated the influence of physicochemical properties of encapsulated functional lipids – vitamin A, β-carotene and ω-3 fish oil – on the structural arrangement of solid lipid nanoparticles (SLN). The relationship between the crystal structure and chemical stability of the incorporated bioactive lipids was evaluated with different emulsifier compositions of a saponin-rich, food-grade Quillaja extract alone or combined with high-melting or low-melting lecithins. The major factors influencing the structural arrangement and chemical stability of functional lipids in solid lipid dispersions were their solubility in the aqueous phase and their crystallization temperature in relation to that of the carrier lipid. The results showed that the stabilization of the α-subcell crystals in the lattice of the carrier lipid is a key parameter for forming stable solid lipid dispersions. This study contributes to a better understanding of SLN as a function of the bioactive lipid.