Estudo e diferenciação do perfil metabólico da Carne do pirarucu - Arapaima gigas (Arapaimidae) fresco e salgado por Ressonância Magnética Nuclear aliada à quimiometria

Abstract

The Pirarucu (Arapaima gigas), also known as Amazon codfish, is widely consumed in the northern region of Brazil, both in its fresh and salted-dried forms. However, to this day, there have been no investigations regarding the molecular chemical composition of its meat and the effects that the salting and drying process, carried out empirically and artisanally to obtain the cured product, directly have on the final quality. In this sense, the objective of this study was to investigate the differences in the metabolic profile of fresh and salted-dried Pirarucu meat using 1H NMR and chemometric techniques. Two experiments were planned for this purpose, in which the samples of salted-dried Pirarucu were produced in the laboratory, and others were collected from commercial sources in 4 zones of Manaus. The samples were macerated with the aid of N2(l) and weighed at 50 mg for direct extraction in 550μL of D2O containing TMSP-d4 in quadruplicate. The mixture was then sonicated for 30 minutes, centrifuged for 10 minutes, and transferred to the NMR tube. The analyses were performed on a Bruker Avance III NMR spectrometer (500.13 MHz) equipped with a BBFO probe. The 1H NMR spectra were acquired in triplicate at 25°C using the ZGPR pulse sequence following the parameters: 32 (NS), 15s (D1), 65K (TD), 4.08 s (AQ), 128 (RG). The pulse (P1) was calibrated for each sample, as well as tuning and matching. The chemometric analyses were performed using the PlsToobox Solo software, version 9.0, and the online site MetaboAnalyst 5.0. The analysis of 1D and 2D NMR spectra allowed for the identification of 29 metabolites, including amino acids, organic acids, carbohydrates, nucleotides, and biogenic amines. In the experiments with commercial and produced samples, PCA revealed that PC1 was sufficient to explain the major variance and was able to differentiate between fresh and salted-dried samples. The metabolites described in the loadings graph in PCA were analyzed by PLS-DA and evaluated using VIP-Scores. For the produced experiment, it was found that the metabolites creatine, glycine, taurine, and acetic acid were responsible for classifying the fresh Pirarucu samples, while only creatinine was responsible for classifying the salted-dried samples. For the experiment with commercial samples, the results showed that only creatine was important for classifying the fresh samples, while the salted-dried samples were classified by the metabolites succinate, creatinine, acetic acid, alanine, dimethylamine, and hypoxanthine. The quantification of these metabolites in Pirarucu meat showed that the fresh matrix had a higher concentration (mM/g) of metabolites related to fish freshness, while the salted-dried Pirarucu matrix had a higher concentration of metabolites related to the degradation products of amino acids and fatty acids, caused by the salting and post-processing of the fish. In addition to providing the first description of the chemical composition of Pirarucu meat, the study showed that the identified compounds are related to fish quality parameters and will be used to discuss, at a molecular level, the salting process and the quality of Pirarucu meat, which can add market value.