Solid lipid nanoparticles as carriers for lipophilic compounds for applications in foods

Nanotechnology is a new subject of interest in the field of food industry. Therefore, scientific and technological studies have been intensified in the last 10 years because of the promising results associated with the potential application of functional properties in food products, such as physical and chemical stability, protection and controlled release of bioactive compounds, and facilitated solubility of lipophilic compounds. Lipids have been used as raw material for the preparation of nanostructures, mainly owing to the solubilization capacity of lipophilic bioactive compounds, as well as because of the advantage of potentially using natural ingredients for production on an industrial scale. Thus, in this review, we describe the information reported in scientific literature on the chemical, physical, and structural properties of lipids used in the preparation of solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs). We reviewed the production methods; structural lipid components; emulsifying systems; bioactive lipophilic compounds; and the physical, thermal, and oxidative properties of SLN and NLC. In addition, important methods for characterizing these systems with regard to particle size, polydispersity index, zeta potential, morphology, crystallization behavior, and polymorphism are discussed with examples, in order to support studies that consider physical stability during processing and storage. Furthermore, studies on the applications of SLNs and NLCs in foods are only found for model systems, justifying the compilation of a series of studies on the potential applications to encourage future works. In addition, we have described the aspects still under discussion, related to the possible risks and regulatory aspects of nanotechnology in food.