Recovery of Astaxanthin from Shrimp Cooking Wastewater: Optimization of Astaxanthin Extraction by Response Surface Methodology and Kinetic Studies

A protein and astaxanthin-concentrated fraction (Rf) can be recovered from shrimp cooking wastewater by ultrafiltration at 300 kDa, indicating that astaxanthin is somehow associated to membrane-retained proteins. Response surface analysis showed that astaxanthin can be extracted from Rf using sunflower oil (3:1 v/v) under milder conditions (T < 40 °C) than directly from shrimp exoskeleton. Modeling astaxanthin extraction kinetics at 30 °C revealed that the process is a consequence of both mass transfer and hydrogen bonding between astaxanthin and oil. The freeze-dried concentrate (FRf) showed two-phase extraction profiles with a much faster pigment recovery observed at 30 °C compared to the liquid form (Rf). The best yields of astaxanthin extraction were not further improved after hydrolysis with alcalase at 45 °C for 30 min (HRf), although higher yields were obtained when both Rf and LRf were extracted in the presence of 200 mg/L butylated hydroxyanisole or ethoxyquin. Astaxanthin from this shrimp by-product has low thermal stability in oil at high temperatures (60 and 70 °C), suggesting the carotenoid is mainly free as a result of the cooking process and not bounded to proteins or lipids as it occurs in its natural form.