The presence of valuable bioactive compounds in European eel (Anguilla anguilla) skin was studied. For it, 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 values. Regarding lipid classes, a higher (p<0.05) proportion of phospholipids (111.1 g·kg-1 lipids), sterols (104.7 g·kg-1 lipids), α-tocopherol (274.0 mg·kg-1 lipids), and free fatty acids (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, as well as for the polyunsaturated/saturated ratio. It is concluded that eel skin, a by-product resulting from commercial processing, can be considered a valuable source to provide the food and pharmaceutical industries with useful value-added constituents such as proteins, lipids, ω3 FAs, phospholipids, and α-tocopherol.

The different vegetable oils used in canned fish as filling medium have a preserving effect and contribute to the palatability of the product. In this study, the colour of European eels and the filling medium (sunflower oil, olive oil or spicy olive oil) was measured at different steps of the canning process. The sensorial characteristics of canned eels packed in the different oils were also evaluated. Colour scores (CieLab values) were higher in canned eels packed in sunflower and spicy olive oil than in canned eels packed in olive oil. The changes in colour parameters depended on the type of oil, the stage of the process and the storage time. Colour changes in canned eels packed in olive oil were highest during the sterilization process. Spicy olive oil was the filling medium in which the colour change was greatest, probably due to the migration of some of the spice components into the oil. Organoleptic properties were directly related to the type of oil used as the filling medium. The canned eels packed in sunflower oil were those awarded the highest scores in consumer tests, although the preferences varied depending on the age and gender of the consumers.