Astaxanthin Extraction from Marine Crustacean Waste Streams: An Integrate Approach between Microwaves and Supercritical Fluids

Marine crustacean waste streams, in particular crab wastes, are promising alternative sources of astaxanthin (ASX), a highly demanded carotenoid with strong antioxidant capacity currently very used for nutraceutical and functional food formulations. However, the composition and rigid structure of crab exoskeleton constitute a critical bottleneck for ASX recovery from these residues. In this work, an extraction strategy is proposed for obtaining an ASX-rich extract from crab shell wastes, integrating microwaves (MW) pretreatment and supercritical fluid extraction (SFE). The multivariate nature of the processes involved is expected to lead to a nonadditive contribution of the individual factors effects on the extract quality and quantity. As such, design of experiments approaches were used to screen and optimize the processes. MW pretreatment with different solvent systems (hydroalcoholic mixtures with 0–50 vol % of water) at different temperatures (40–140 °C) were applied followed by conventional solvent extraction for crab shell structure disruption. Different SFE conditions, namely pressure (200–500 bar), temperature (40–60 °C), ethanol content in the supercritical CO2 (8–13 wt %), and equilibration time (0–30 min) were also explored in order to selectively recover ASX. Optimized operating conditions of each process individually were selected and ASX extraction efficiency through the integrated MW pretreatment and SFE strategy was assessed. All the extractable ASX was selectively recovered 12 times faster than traditional Soxhlet extraction, demonstrating that the proposed extraction approach significantly improves the extraction efficiency. This study suggests that integration of MW pretreatment with SFE can be considered a good strategy for intensification of ASX extraction from crab residues. With this extraction approach, not only have marine crustacean waste streams been valorized, but also a high added value natural ingredient has been isolated, allowing for its subsequent use.