Advances in fish oil extraction and enrichment: a comprehensive review of conventional and green technologies for high-quality omega-3-rich oil production

Omega-3 polyunsaturated fatty acids (PUFAs), particularly eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA), are well-known for their therapeutic potential, especially in their cardiovascular, anti-inflammatory, and neuroprotective roles. The primary dietary source of these bioactive compounds is fish oil. However, extraction methods require careful attention to ensure the production of high-quality omega-3 rich oil, while also aligning with green chemistry principles, environmental sustainability, and growing market demands, all of which place industries under pressure to balance between efficiency, safety, and cost. Conventional extraction methods, including mechanical (e.g., wet pressing and cold pressing) and solvent-based approaches (e.g., Soxhlet, Folch, Hara–Radin), are often associated with the oxidation and degradation of thermolabile compounds like omega-3s, in addition to posing environmental and occupational hazards. As a result, a shift toward green and advanced extraction techniques (e.g., ultrasound-assisted, microwave-assisted, enzymatic-assisted, and supercritical fluid extractions) offers a more sustainable alternative, although their industrial application remains limited due to high operational costs and scalability challenges. However, even with milder green technologies, losses of EPA, DPA, and DHA still occur, necessitating an enrichment step to meet regulatory standards and consumer demand for omega-3-rich supplements. Current enrichment strategies such as molecular distillation, membrane-based filtration, and enzymatic purification, have undergone various improvements but still struggle with some challenges that limit their application, such as low DHA selectivity, process optimization, and enzyme instability. This review provides a comprehensive overview of conventional and green extraction methods, as well as enrichment strategies, highlighting their principles, applications in fish oil, advantages, limitations, and industrial feasibility. Additional research is required to further improve these technologies and address current limitations, with the goal of integrating them into scalable systems that support the production of high-quality omega-3-rich oil. This is also particularly crucial when combined with the upcycling of fish by-products, offering a more sustainable and effective approach that aligns with green chemistry and circular economy principles.