Avaliação do efeito do Sulfato de amónio na extracção de lípidos e bases voláteis totais de nitrogenio (BVT-N) em bagre africano (Clarias gariepinus) e camarão rosa (Metapenaeus monoceros)

Abstract

This study aimed to evaluate the effect of ammonium sulfate on the extraction of lipids and total volatile base nitrogen (BVT-N) in African catfish (Clarias gariepinus) and pink shrimp (Metapenaeus monoceros) at different concentrations (0.1%, 0.3%, and 0.5%). The methodology was based on the fortification of samples with ammonium sulfate, followed by analysis at different time intervals (0, 2, 4, and 6 days), applying standardized laboratory techniques such as Soxhlet extraction for lipids and steam distillation for the determination of BVT-N. The pH was measured with a digital pH meter after homogenization of the samples in tetraacetic acid solution. The results demonstrated that the addition of ammonium sulfate significantly influenced the evaluated parameters. For African catfish, a progressive increase in BVT-N values was observed with increasing ammonium sulfate concentration, reaching 120.96 mg/100g with 0.5% ammonium sulfate. The lipid content also increased, reaching 2.70% under the same conditions. In pink shrimp, the same pattern was identified for BVT-N, with a maximum of 143.09 mg/100g, but the lipids presented distinct peaks, with the highest value (0.424%) recorded with 0.1% ammonium sulfate. The pH remained stable in the fortified samples, demonstrating the ability of ammonium sulfate to limit acidity. The discussion established that ammonium sulfate acts as a protein precipitator, facilitating the extraction of lipids and volatile compounds relevant to characterizing fish quality. Furthermore, the results show that African catfish had higher lipid levels than pink shrimp, while the latter had a higher concentration of volatile nitrogen compounds. It is concluded that the application of ammonium sulfate, combined with controlled exposure time, may represent a viable strategy for characterizing fish lipid content, contributing to improving the biochemical utilization of the species studied.