Fabrication of astaxanthin emulsion and effect of cellulose derivatives

Introduction: Astaxanthin, a highly active oxidant, possesses a potential effect on human health. However, with the oily characteristic, the ability to disperse in an aqueous environment has limited its application. Therefore, the aim of this study is the fabrication of a stable astaxanthin emulsion in water. Methods: In this study, an emulsion of astaxanthin was fabricated using polysorbate (tween 60/80) or lecithin. The dispersing methods of the magnetic stirrer and stator-rotor ho-mogenizer were applied and compared. The effect of cellulose derivatives (sodium carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC), and hydroxypropyl methylcellulose (HPMC)) on the astaxanthin emulsion system was investigated. The samples were characterized using dynamic light scattering (DLS), a Brookfield viscometer and Fourier transform infrared (FTIR) spectroscopy. Results: The homogenization could provide the system with a small Z-average value ( ~ 500 nm). The emulsion fabricated with lecithin maintained the red color of as-taxanthin and homogeneity even after 5 months. Tween 80 had the worst effect on astaxanthin degradation because of the presence of double bonds in the surfactant's molecular structure. The addition of soluble cellulose could significantly reduce the particle size and polydispersity even by using a magnetic stirrer. However, it could not ensure the protection of astaxanthin when phase separation was detected in many samples with polymers. The FTIR spectra and viscosity results revealed the strong interaction of lecithin with CMC, HEC, and HPC, which might be the reason for the low stability of the system. HPMC exhibited the best capability to stabilize and preserve the astaxanthin emulsion. Without using the high-energy dispersing method, a particle size of 482 nm (polydispersity index: 0.51) could be obtained with the HPMC-lecithin astaxanthin emulsion. Conclusions: A stable astaxanthin emulsion (up to 5 months) could be fabricated successfully. The conventional homogenizer could form a better emulsion with a single surfactant. However, cellulose derivatives could assist the emulsion to have better DLS results even with the magnetic stirring method. Lecithin showed better performance in astaxanthin preservation than polysorbate surfactant. Strong interactions of lecithin with CMC, HEC, and HPC were detected. However, the addition of HPMC could provide a system with a lower particle size and high astaxanthin stability. The study could open a new approach for fabricating a stable astaxanthin emulsion using the low shear mixing method.