Fabrication of β-carotene loaded alginate oleogels by the aerogel template method: Impact of pressure and temperature of supercritical carbon dioxide drying

Oleogels are semi solid gel matrices, which are primarily constructed by entrapping liquid oil in a network of oleogelators such as waxes. However, oleogels can also be formed from hydrophilic biopolymers by exploiting the oil structuring ability of aerogel templates. This entails the formation of a hydrogel, followed by supercritical carbon dioxide (scCO₂) drying to form aerogels which can be directly immersed in oil to form oleogels. However, the uptake of oil is dependent on the microstructure of the aerogel, which is determined by the process parameters of the scCO₂ drying. In this study, the effect of pressure (100, 200 bar) and temperature (45, 55 and 65 °C) was studied on the resultant physical properties of the aerogel. A higher bulk density and a lower porosity at higher pressures and temperature (200 bar|55 and 65 °C) indicated a structural collapse, which had a detrimental effect on the bulk properties of the aerogels. The specific surface area of the aerogels ranged between 39.4 and 279.1 m²/g, wherein the highest value was observed at 200 bar and 45 °C. This was also reflected in the highest swelling index (39.9 g/g), oil absorption capacity (17.8 g/g) and surface morphology of aerogels. The aerogel (200 bar|45 °C) exhibited a greater loading of β-carotene (348.4 μg/g) than the cryogel (238.2 μg/g). This trend can be attributed to the greater pore diameter (∼11.98 nm) and volume (0.447 cm³ g⁻¹) of the aerogel. The oleogels developed thereof facilitated a controlled in-vitro release of β-carotene in the simulated intestinal fluid.