It is estimated that in EU-28, 88 million tons of food are wasted every year, with 143 billion euros of associated costs. For this reason, reducing food loss is now an integral part of European Commission's Circular Economy Package, aiming at ensuring a sustainable growth and development. Among all wasted food, crustaceans and mollusc are a major source of surpluses when processed for human consumption, generating solid residues equivalent to 20-50% of the starting raw materials.

In the last years several studies pointed marine by-products as a remarkable source of important bioactive molecules, such as proteins, peptides, amino acids, lipids, biopolymers, enzymes, pigments, vitamins and minerals. These compounds can be used in a broad range of economically interesting applications, including nutraceutical formulations, cosmetics or in biomedical and pharmaceutical industries, holding a much higher market value than conventional applications for shellfish by-products. Natural Deep Eutectic Solvents (NADES), have emerged as innovative solvents that can act as selective extractants, while ensuring the environment and consumers’ health protection. NADES are based on mixtures of two or more natural compounds, which can include amino acids, sugars, organic acids, terpenes, choline derivatives (e.g. choline chloride, ChCl), etc. Their low cost production, high purity, biodegradability, pharmaceutically acceptable toxicity and biocompatibility offer enormous potential to convert shellfish processing streams into high-added value compounds.

In this work, NADES, i.e. ChCl:xylose (3:1), betaine:malic acid (2:1), menthol:camphor (1:1), menthol:limonene (1:1), menthol:lauric acid (4:1) and menthol:myristic acid (8:1) were used for the recovery of bioactive compounds from shellfish by-products. NADES were characterized and their physicochemical properties (i.e. viscosity, density, conductivity, polarity, surface tension and thermal behaviour) determined. Extraction with conventional organic solvents was also performed for comparison.

Based on the results obtained, NADES showed to be a good alternative to traditional solvent extraction methods, thus giving an important contribute for the valorisation of side streams generated by the shellfish industry, within the biorefinery concept.