Binary mixtures of menthol and alkanoic acids as green solvents for efficient astaxanthin recovery from Aristaeomorpha foliacea shrimp shells

The seafood industry generates large volumes of waste, responsible for serious environmental hazards and high disposal costs. Bioconversion and biorefinery approaches offer effective management of seafood waste, preserving valuable nutrients and supporting sustainable seafood production. Shrimp shells are a rich source of polyunsaturated fatty acids and carotenoids, mainly astaxanthin (AST), whose recovery by means of green strategies represents a challenging goal. In this work, the potential of equimolar binary mixtures of menthol and alkanoic acids (ME:AA) as green solvents for AST recovery from shells of Aristaeomorpha foliacea (Risso, 1827) shrimp has been explored, by evaluating both the yield and the stability of the extracted carotenoid. All tested ME:AA exhibited high efficiency for fast AST extraction in mild conditions, while the mixtures containing acetic (ME:C2) and decanoic (ME:C10) acids ensured the maximum stability of the pigment. HPLC analysis highlighted a variety of extracted AST derivatives, mainly consisting of mono- and diesters of fatty acids with variable side chains. Their overall amount allowed to identify mediterranean A. foliacea as a shrimp species particularly capable of AST uptake and storage. ATR-FTIR measurements pointed out partial deprotonation of the alkanoic acid component following the extraction process, in agreement with the alkalinity of the CaCO3-rich matrix. Interestingly, the antioxidant capacity of the extracts exceeded the predicted one, based on the AST content, suggesting the co-extraction of additional antioxidant compounds. Finally, α-cyclodextrin was successfully employed as emulsifying agent to prepare stable ME:C10-in-water microemulsions, which drastically enhanced the chemical stability of extracted AST under standard environmental conditions.