The Presence of Bioactive Compounds in European Eel (Anguilla anguilla) Skin: A Comparative Study with Edible Tissue

The presence of bioactive compounds in European eel (Anguilla anguilla) skin was studied. Proximate and lipid class compositions and analysis of the fatty acid (FA) profile (individual FAs; FA groups, i.e., saturated, monounsaturated, and polyunsaturated; FA ratios, i.e., polyunsaturated/saturated, ω3/ω6) were determined and compared to the composition of the eel muscle. As a result, higher (p < 0.05) levels of proteins (271.6 g·kg^-1), lipids (38.0 g·kg^-1), ash (27.7 g·kg^-1), and ω6 FAs were observed in the skin tissue. Contrary, the muscle tissue showed higher (p < 0.05) moisture, ω3 FA, and ω3/ω6 ratio values. Regarding lipid classes, a higher (p < 0.05) proportion of phospholipids (111.1 g·kg^-1 lipids), free sterols (104.7 g·kg^-1 lipids), α-tocopherol (274.0 mg·kg^-1 lipids), and free FAs (43.6 g·kg^-1 lipids) was observed in the skin tissue. No differences (p > 0.05) between both tissues could be detected for triacylglycerol and FA group (saturated, monounsaturated, and polyunsaturated) values and for the polyunsaturated/saturated FA ratio. It is concluded that European eel skin, a by-product resulting from commercial processing, can be considered a valuable source for the food and pharmaceutical industries by providing value-added constituents such as proteins, lipids, ω3 FAs, phospholipids, and α-tocopherol.