Determining the Potential of Haematococcus pluvialis Oleoresin as a Rich Source of Antioxidants

Abstract

Haematococcus pluvialis is known to be a natural source of antioxidants for numerous applications. In this study, an oleoresin rich in carotenoids extracted by supercritical CO₂ treatment of H. pluvialis was extensively characterized for its antioxidant capacity. Carotenoid content, fatty acid profile, total phenol content, antioxidant capacity, and viscosity of the oleoresin were determined with the aim of ascertaining the potential of the oleoresin in terms of its antioxidant content for food applications. The oleoresin contained 96.22 mg/g of total astaxanthin (which includes free astaxanthin and astaxanthin esters) and mostly included unsaturated fatty acids (~78% of total fatty acids). High total phenol content and ferric reducing antioxidant potential indicated high antioxidant capacity, but oxygen radical absorbance capacity was lower compared to the oleoresin samples obtained from other species. The oleoresin was a non-Newtonian fluid since it had shear-thinning (pseudoplastic) and shear-thickening (dilatant) flow. Therefore, the H. pluvialis oleoresin is a potential alternative in developing functional ingredients for designing healthy food products. To the best of our knowledge, this is the first study that has reported an extensive characterization of the antioxidant properties of a microalgal oleoresin obtained by means of supercritical CO₂ fluid extraction.

Keywords: Haematococcus pluvialis; antioxidant capacity; astaxanthin; oleoresin; phenol content; supercritical fluid extraction; viscosity.

Figure 1

Fatty acid composition of the oleoresin extracted by SC-CO₂ from the microalga Haematococcus pluvialis determined by GC-FID. SFA: saturated fatty acids, MFA: monounsaturated fatty acids, and PFA: polyunsaturated fatty acids. All data are measured as the percentage of total fatty acid methyl esters (% area; n = 3; ±SD).

Figure 2

Rheogram flow curve of oleoresin at different temperatures with a relationship between shear stress (τ; Pa) and shear rate (γ; s⁻¹). (A) Low temperatures from 5 to 20 °C (with spindle SC–21; n = 3) and (B) high temperatures from 30 to 60 °C (with spindle SC–27; n = 3).

Figure 3

Temperature effect on the apparent viscosity of oleoresin at different shear rates. (A) Low temperatures from 5 to 20 °C (with spindle SC–21; n = 3) and (B) high temperatures from 30 to 60 °C (with spindle SC–27; n = 3).