Determination of potassium, sodium, and manganese in textured soy protein by instrumental neutron activation analysis and gamma-ray spectrometry.

Glycine max, commonly known as soybean, is one of the most widely cultivated legumes in Brazil and represents a nutritionally relevant source of proteins, lipids, dietary fibers, and essential minerals. In the form of textured soy protein, it constitutes a low-cost alternative to animal-derived proteins, with potential to support food security strategies, reduce social vulnerability, and inform public policies aimed at improving access to nutritious foods. This study aimed to identify and quantify potassium, sodium, and manganese in a commercial textured soy protein product purchased from a local market in Rio de Janeiro, Brazil. The analytical approach combined Instrumental Neutron Activation Analysis (INAA), using the comparative method, with Gamma-Ray Spectrometry (GRS). Irradiations were performed in the Argonauta reactor at the Instituto de Engenharia Nuclear, operating at 34 W and a thermal neutron flux of 108 n·cm-2·s-1 for 30 min. After irradiation, induced radionuclides were measured by GRS using a high-purity germanium detector with 25% relative efficiency and 1.8 keV resolution at the 1332 keV photopeak of 60Co, together with the DSPEC jr 2.0 system and Maestro v7.0 software. Element identification was based on gamma energies and half-life confirmation, while quantification used the INAA method. Concentrations were 1576.05 ± 25.54 mg/100 g for potassium, 4.55 ± 0.76 mg/100 g for sodium, and 2.30 ± 0.18 mg/100 g for manganese. The results demonstrate the applicability of INAA and GRS for multielemental analysis in food matrices and indicate a favorable nutritional profile for the analyzed textured soy protein product, particularly its high potassium and low sodium content.