The aim of this study was to investigate the efficiency of different extraction methods for total lipid determination and oxidative rancidity evaluation in freshwater fish with different fat levels. Total lipid content was determined by Bligh and Dyer with slight modifications and Soxhlet methods. Malondialdehyde (MDA) quantification was determined by analytical methods with and without heat application. In both freshwater fish species, Bligh and Dyer method extracted greater total lipid content (P <0.05) than Soxhlet method. In addition, the heat method revealed higher MDA values (P <0.05) compared to cold method in both lean fish (Cichla ocellaris) and high-fat fish species (Piaractus brachypomus). We concluded that, regardless of the fat content in the freshwater fish species, the Bligh and Dyer method and the cold method used for oxidative rancidity were more efficient than Soxhlet method and heat technique, respectively.

The striped catfish (Pangasianodon hypophthalmus), exported mainly by Vietnam, has been widely accepted by global consumers due to its white meat and low cost. However, the highly perishable nature of fish requires the use of alternative technologies to ensure quality and safety for prolonged storage periods under refrigeration. This study investigated the effect of UV-C radiation (1.95 mW/cm 2 for 90 s) on biochemical quality parameters of striped catfish fillets stored at 4 °C for 9 days. Refrigerated samples were analyzed for biogenic amines, pH, total volatile basic nitrogen (TVB-N), ammonia, and lipid oxidation. UV-C-treated fillets had lower (P < 0.05) levels of TVB-N, ammonia, and biogenic amines, and higher (P < 0.05) lipid oxidation than untreated fillets during the storage period. UV-Ctreated fillets had higher (P < 0.05) pH levels than untreated fillets until day 5 of storage, although both had similar pH levels (P > 0.05) on days 7 and 9. This technology is a possible alternative for conservation of striped catfish fillets, but other doses of UV-C must be evaluated to mitigate or prevent the negative effect on lipid oxidation observed here.