Desenvolvimento de método analítico para análise multielementar e determinação da fração bioacessível em lentilha e ervilha por MIP OES

Abstract

Legumes are highly nutritious foods because they are rich in vitamins, fibers, proteins, minerals and bioactive compounds. In addition to nutritional benefits, the cultivation of legumes generates an increase in agricultural productivity in a sustainable way. Since 2018, World Legumes Day is celebrated on February 10th with the aim of emphasizing the benefits and encouraging their consumption. Therefore, the present study aims to develop an analytical method for the determinations of Al, B, Ba, Cu, Fe, K, Mg, Mn, V and Zn in lentil and pea samples (in natura and cooked) and to evaluate the bioaccessible fractions of Ba, Cu, Fe, Mg, Mn and Zn. For this, the acid decomposition with reflux system as sample preparation method was used and the conditions of sample mass, H2O2 volume, temperature and decomposition time were optimized, fixing a volume of 5 mL of HNO3. The most appropriate conditions were 1 g of sample, heating temperature of the digester block at 150° C, 4 hours of decomposition and 5 mL of H2O2 35% (v/v) at 120°C. The quantification of the elements was performed using the Microwave Induced Plasma Optical Emission Spectrometry (MIP OES) technique. The proposed method proved to be efficient, obtaining a low residual carbon content for lentil and pea samples (fresh and cooked). The accuracy of the method was evaluated through addition and recovery tests, analysis of CRM-Agro C1003a certified reference material and analysis of the CRM-Agro c1003a mixture with lentil sample. The highest total concentrations obtained in lentil and pea samples were for K, Mg, Fe and Zn. After the samples go through the cooking process, there was a decrease and/or a significant increase in the concentrations of some elements. Decreases in concentrations may be due to the leaching process during cooking, while increased concentrations may be related to the presence of antinutritional factors. The highest bioaccessible percentages in the cooked lentil was for Mg, Mn, Zn and Cu, while in the cooked pea it was for Mg and Cu. Pearson's correlation analysis between polyphenol contents and bioaccessible concentrations showed that polyphenols can generate an inhibiting effect on the bioaccessibility of some elements, especially for Fe, which obtained bioaccessible fractions lower than the analyte detection limits for all samples, except pea sample 2. The bioaccessible fractions of the minerals for both samples were below the recommended daily intake, but they can contribute together with other foods, to complement the amount of recommended daily intake of the minerals.