Sussi López-Puebla

Fish are generally rich sources of n-3 polyunsaturated fatty acids such as EPA and DHA, and although the edible part (fillet) has been analyzed in many species, less is known about the composition of fish by-products. The analysis of these materials allows them to be evaluated as raw sources of EPA and DHA, thus contributing to sustainable practices to produce healthy oils for human consumption. This work provides information on the fatty acid profiles, lipid quality indices and α-tocopherol, squalene and cholesterol contents in fillets, heads, bones and viscera of three fish species (anchovy, chub mackerel and Chilean jack mackerel). Samples were lyophilized and lipids were extracted using either the Folch or Hara and Radin methods. FA profiles were obtained by gas chromatography coupled with flame ionization detection, and tocopherol, squalene and cholesterol analyses were performed by high performance liquid chromatography with UV-visible detection. The highest levels of EPA were found in anchovy fillet (18.9–20.6%) and bone (14.7%), while DHA was more abundant in anchovy fillet (16.9–22.0%) and Chilean jack mackerel fillet (15.4–16.6%) and bone (13.1–13.8%). α-Tocopherol, squalene and cholesterol contents ranged from 0.18 to 1.35 mg/100 g, 0.07 to 0.80 mg/100 g and 30.46 to 246.17 mg/100 g, respectively, in the different tissues analyzed from the three fish species.

This study developed, validated, and tested a simple method for tocopherol analysis on five different food matrices (sunflower oil, mackerel fillets, almonds, spinach, and avocado pulp). Tocopherol extraction from foods was carried out by the Folch method and with n-hexane, and the identification and quantification of tocopherol isoforms (α, β, γ, and δ) was performed using normal-phase liquid chromatography with ultraviolet–visible detection (NP-HPLC–UV–Vis). The normal-phase column fully separated the four tocopherol isoforms in less than ten minutes. Linearity was shown to be excellent for the four isoforms in the assayed range (10–375 ppm, R² > 0.99). Furthermore, the limits of detection (LOD) and quantification (LOQ) ranged from 0.32 to 0.63 ppm, and from 1.08 to 2.11 ppm, respectively. The intra-day and inter-day precision were assessed at different concentrations (10, 100, and 250 ppm) for each tocopherol isoform and they were within the range of acceptable values. Recovery rates were above 80% in most cases for all of the assayed food matrices, regardless of the extraction method (Folch solvents or n-hexane). α-Tocopherol was the main isoform found in all tested foods, and sunflower oil was the sample with the highest content, followed by almond, avocado pulp, mackerel fillet, and spinach. This method provides a convenient alternative for obtaining a complete profile of the four tocopherol isoforms in a variety of food matrices and for tracking the potential degradation kinetics of fortified foods during their processing and storage.