A review of defatting processes using sustainable solvents: parallels between seed and fish oil sources

Abstract

Conventional defatting and oil removal processes, employed for both oilseed and fish biomasses, are mainly based on petrochemical solvents like hexane. The noteworthy drawbacks of these efficient methods include the presence of residues in the products, environmental pollution, and high risks for the operators. This review aims at comparing conventional hexane extraction with alternative and sustainable defatting solvents, highlighting the parallel advantages, limitations, and research gaps identified in seed and fish oil processing. Current advances in clean and sustainable defatting solvents, including alcohols, terpenes, deep and natural deep eutectic solvents, ionic liquids, 2-methyloxolane, supercritical carbon dioxide, and vegetable oils, are covered, emphasising their chemical, physical, and safety properties. Actual constraints, mainly in terms of economic and technical feasibility and applicability, or industrial exploitation and scalability, are also mentioned, along with possible approaches for a more successful employment of these promising solvents. In this review, a parallel evaluation is also made in terms of main gaps and perspectives related to diverse pre-treatments for the optimisation of seed and fish defatting.