Applicability of a green extraction method assisted by microwaves (MAE) coupled to a Multivapor system for the rapid extraction of fish lipids

The lipid content in fishery food is typically estimated using the Soxhlet method, the officially recommended method (AOAC, 2005) [1]. Alternative methods like the Folch method (1957), which uses a chloroform/methanol/water system, are considered reliable for quantitative lipid extraction. Despite modifications, conventional methods (Bligh and Dyer, modified Bligh & Dyer, modified Folch, Roese-Gottlieb, Hara & Radin) still require long preparation times and re-extraction steps [2]. Furthermore, these methods pose challenges for product quality as high temperatures can degrade heat-sensitive compounds, and/or toxic solvents may leave residues in the final product. They also have a higher environmental impact due to significant heat requirements and/or the risk of solvent leakage. Over the past two decades, green extraction methods have emerged as a promising alternative to overcome the disadvantages of these conventional methods [3]. The green extraction method focuses on reducing energy usage, using alternative solvents and renewable materials, and producing safe, high-quality extracts. New technologies like Supercritical Fluid Extraction (SFE), Pressurized Liquid Extraction (PLE), and Microwave-Assisted Extraction (MAE) have been developed for total fat extraction. MAE, in particular, uses microwave energy to heat solvents, improving lipid yields and reproducibility. It is a rapid and effective alternative to conventional methods, offering advantages such as shorter extraction times, fewer residues, reduced solvent consumption, and lower environmental toxicity. The closed containers in MAE prevent the loss of volatile compounds. Additionally, the straightforward nature of the microwave method minimizes the need for manual labor and boosts overall productivity. Furthermore, the coupling with a Multivapor system (Multivapor P-12/Rotavapor R-300 (BÜCHI Labortechnik AG, Switzerland), which performs the efficient evaporation of multiple samples (12 samples) simultaneously, maximizes the efficiency of the whole process (in less than 1 hour, the lipid recovery of 12 samples is performed). In this study, MAE was chosen as the green extraction method to isolate the lipid fraction of aquaculture Mugil Cephalus samples (fillets and livers) fed with different diets in the frame of a PNRR project (namely Spoke 2 Activity 3 of National Biodiversity Future Center- NBFC). MAE was performed using an ETHOS-X microwave system (Milestone S.r.l., Sorisole, Bergamo, Italy) with 100 mL Teflon vessels, optimizing the protocol developed by Costa et al. [4]. The solvent mixture used was ethyl acetate/ethanol in a 2/1 ratio, with a solid/solvent ratio of about 1/14. Each sample was heated to 60°C for 15 minutes, then reduced to 25°C, with a maximum extraction power of 1000 W. The recovery capacity of the free lipid fraction was assessed using a reference sample of fish tissue with known lipid content (crude fat 6% ± 0.35%). The recovered lipids were analyzed to assess their oxidation status and their fatty acid composition. References [1] W. Horwitz (Ed.), Method 989.05 (18th ed.), AOAC International, Arlington, USA (2005) [2] M. J. Ramalhosa, P. Paíga, S. Morais, M. Rui Alves, C. Delerue-Matos, M. B. Prior Pinto Oliveira, Food Chemistry, 2012, 131, 328. [3] K. Ivanovs, D. Blumberga, Energy Procedia, 2017, 128, 477. [4] D.d.S.V Costa, N. Bragagnolo, European Journal of Lipid Science and Technology, 2017, 119,1600108