Encapsulation of Microalgae <i>Haematococcus pluvialis</i> Containing Astaxanthin Using Refined Olive Oil and Octenyl Succinic Anhydride Modified Starch

The aim of this study was the encapsulation of Haematococcus pluvialis containing astaxanthin (HAST) using emulsion prepared with refined olive oil and octenyl succinic anhydride (OSA) modified starch. Thus, emulsions were prepared by different concentrations of OSA-modified starch (5%, 10%, and 15% w/w) and their physicochemical (encapsulation efficacy, size, zeta potential, solubility, and stability), structural, and morphological properties were investigated. According to the results, the zeta potential of emulsions was in the range of -6.73 to -15.10 mV and the negative charge of droplets caused electrostatic repulsion and improved the emulsion stability. The emulsion prepared with higher concentration of OSA-modified starch had higher stability (p <0.05). Droplet size of emulsions was in the range of 322.23 ± 6.30 to 191.50 ± 3.91 nm, and the smaller droplet size was at a higher concentration of OSA-modified starch (p <0.05). Also, the highest encapsulation efficacy (EE)% was observed by emulsion stabilized with 10% w/w OSA-modified starch (91.13 ± 0.35%) (p < 0.05). Color parameters showed that a higher concentration of OSA-modified starch caused an increase in L*, WI, and ΔE and reduction in a* and b* values. Fourier transform infrared spectroscopy (FTIR) revealed successful encapsulation of astaxanthin. Microcapsules embedded with OSA-modified starch at all concentrations showed uneven surfaces with dented areas but no visible cracks. As the concentration of OSA-modified starch increased, solubility declined. The higher stability was associated with the samples with 10% OSA- modified starch at 4°C and 25°C. This study suggests that emulsion prepared with 10% OSA-modified starch and refined olive oil is a suitable carrier for the encapsulation of hydrophobic compounds.