Haematococcus pluvialis is the largest producer of natural astaxanthin in the world. Astaxanthin is a bioactive compound used in food, feed, nutraceutics, and cosmetics. In this study, astaxanthin extraction from H. pluvialis by supercritical fluid extraction was evaluated. The effects of temperature (40 and 50 °C), pressure (40 and 50 MPa), and CO₂ flow rate (2 and 4 L/min) were investigated. The results showed that the highest astaxanthin recovery was obtained at 50 °C/50 MPa and the CO₂ flow rates evaluated had no significant effect. It was possible to achieve astaxanthin recoveries of 95% after 175 min for a CO₂ flow rate of 2 L/min, and 95 min for CO₂ flow rate of 4 L/min. The ω-6/ω-3 ratios obtained were similar in all conditions, reaching 0.87, demonstrating that the extracts from H. pluvialis by SFE are rich in unsaturated fatty acids (UFA) which increases their positive effects when used as a functional ingredient in food.

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.

Astaxanthin is a powerful antioxidant, because it neutralizes free radicals and plays a vital role in the prevention of human diseases. The objective of this work was to develop an isotonic beverage (IB) of orange-red color, using an astaxanthin oleoresin emulsion (AOE) that is dispersible in water. This was carried out in order to simulate the color of commercial isotonic beverages (CIB) prepared from artificial pigments. The size of the AOE micelles ranged from 0.15 to 7.60 µm². The color difference (ΔE) was similar for the samples exposed to dark as well as light conditions. The samples subjected to light stress showed pigment degradation after seven days, followed by a decrease in the concentration of astaxanthin; whereas, the samples exposed to dark conditions remained stable for seven days and then showed a decrease in the concentration of astaxanthin (this decrease ranged from 65% to 76% when compared to the initial content) after a period of 91 days. For the astaxanthin oleoresin (AO) and AOE, the oxygen radical absorbance capacity (ORAC) values reached 5224 and 1968 µmol of trolox equivalents (TE)/100 g, respectively. When exposed to light conditions, the addition of AOE in the IB led to its rapid degradation, while it remained stable in the samples exposed to the dark conditions.

Microencapsulation protects different bioactive compounds (anthocyanins) from environmental factors, increasing their half-life. In this study, the extraction and microencapsulation conditions for purple cabbage anthocyanins were determined, in addition to stability of the natural pigment obtained in a fermented milk beverage. Scalded was used for enzymatic inactivation in purple cabbage (Brassica oleracea L. ssp. Capitata f. Rubra) leaves, the extraction of bioactive compounds was carried out using green technologies (microwaves), concentrating the anthocyanin solution and mixing with wall materials such as maltodextrin, inulin and gum arabic for microencapsulation and addition to fermented milk beverage. The color stability was determined for 8 days; the ΔE of the beverage was slightly perceptible by the human eye. The concentration of anthocyanins was 199 mg/L with a solution of water and 2% acidified ethyl alcohol at 880 W of power for 90 s; the best drying performance was 58.9%.

Macroemulsions facilitate the solubilization, stability, bioaccessibility, and bioactivity of compounds with low solubility, as is the case of the emulsion developed from astaxanthin oleoresin (10%). In this study, some characteristics of the physical behavior of the macroemulsion with astaxanthin oleoresin that are in close relationship with stability were determined. One of them was the viscosity at 5, 10, 20 and 30°C. Another, corresponded to observing the size variation of the micelles, observed under the microscope for 8 days and finally, the color was determined in CIEL*a*b* system for 34 days. The results showed that the macroemulsion behaved like a shear thinning fluid up to 20°C, becoming a shear thickening fluid at 30° C. In addition, the macroemulsion presented stability in the color as time elapsed; observing some slight variations that may be due to flocculation and coalescence. Both affect the viscosity at low temperatures.