Miniaturização de método de extração de lipídios em peixes e incorporação do ácido docosahexaenóico em Piaractus mesopotamicus

Abstract

In this work, the development and internal validation of the methodology of miniaturized extraction of lipids in mechanically separated meat (CMS) of pacu fish Piaractus mesopotamicus was carried out, followed by chromatographic analysis using a gas chromatograph with flame ionization detector (GC-FID) and using methyl tricosanoate (C23:0) as an internal standard for quantification of docosahexaenoic acid (DHA). CMS samples were subjected to previous studies, evaluating the lipid content of the samples in natura, lyophilized and after drying in an oven at constant weight. The lipids were extracted using the Bligh and Dyer reference method, as a comparison of the information obtained between methods, it was observed that in both cases the CMS prepared at 105°C for 24h with constant weight obtained the best results. results of extracted lipids, being the miniaturized of 19.44% ± 0.88 and the amount of DHA obtained of 0.042 mg/100g. Tests with different solvent portions were also analyzed and it was observed that the best portion found was with the dichloromethane:methanol (2:1, v/v) mixture. The miniaturized method was applied to the Doehlert matrix with the variables of sample mass and homogenization time, obtaining results from a linear model with the explainable variable of 96.08%. After this step, the validation method for the determination of DHA was performed and the results showed excellent performance with low limits (LOD, LOQ, 0.0039 mg/100g and 0.0129 mg/100, respectively), good accuracy ( between 90.95%, 96.24% and 102.44%) and precision (for repeatability and intermediate precision averaging 2.1% and 3.4%, respectively), also being observed good selectivity and linearity. The miniaturized method was applied to a sample of CMS fish Piaractus mesopotamicus fed with 4 different levels of microalgae Schizochytrium sp. incorporated into the feed and a control without the microalgae with 550 specimens distributed among the net tanks for a period of 60 days. Fish were collected every 15 days and analyzed for CMS. The miniaturized method proved to be an excellent alternative for reducing extraction reagents and analysis time compared to the Bligh and Dyer reference method for Piaractus mesopotamicus CMS. The results obtained from the incorporation of the microalgae into the feed showed that the highest concentrations of DHA of the CMS of Piaractus mesopotamicus were obtained after 45 days of feeding at concentrations of 3 and 4% of inclusion of the microalgae Schizochytrium sp.