Preparation of solid lipid nanoparticles and nanostructured lipid carriers containing zeaxanthin and evaluation of physicochemical properties

Zeaxanthin is a yellow carotenoid antioxidant concentrated in the macula. This pigment in many foods and beverages is very problematic due to its extreme hydrophobicity and poor chemical stability. Solid lipid nanoparticles (SLNs) and nanostructure lipid carriers (NLCs) were prepared using a combination of high shear homogenization and ultrasonic methods to load zeaxanthin and reduce its hydrophobicity. In this study, NLCs containing zeaxanthin were produced and optimal formulation was determined and their physicochemical properties were investigated. 20% percent of solid lipid was replaced with Medium-chain triglyceride (MCT) as a liquid lipid to produce NLCs. Results showed that the particle size (PS) of NLCs did not exceed 130 nm, but SLNs did show larger sizes. In addition, particle dispersion index (PDI) showed 0.23 ± 0.01 to 0.34 ± 0.01 and 0.23 ± 0.01 to 0.30 ± 0.01 for SLN and NLC, respectively. Zeta potential (ZP) represented −20.03 ± 0.48 to −12.11 ± 0.80 and −22.23 ± 0.41 to −16.88 ± 0.61 for SLN and NLC, respectively. Encapsulation efficiency and loading were higher for NLCs than SLNs. The morphological study of nanocarriers performed by scanning electron microscope (SEM) showed smooth spherical nanoparticles. Results of Fourier transform infrared spectroscopy (FTIR) analysis, and differential scanning calorimeter (DSC) showed that zeaxanthin was trapped in the nanocarriers without any chemical interaction with the coating material. Glycerol mono-stearate containing zeaxanthin showed phase separation after 60 days at 4 and 25 °C, while this was not observed in nanocarriers produced by glycerol distearate. Together, these nano-based carriers can be applied in many products, especially as nanocarriers for hydrophobic bioactive compounds in nutraceutical beverages.