Avaliação da concentração total e fração bioacessível de elementos essenciais e potencialmente tóxicos em amaranto, quinoa e chia por MIP OES

Abstract

Pseudocereals (amaranth, chia and quinoa) are on the rise because they are functional foods and the minerals present in their composition are responsible for some of the benefits to human health that these foods can provide. Therefore, it is important to know the mineral composition of these foods, evaluating not only the total concentration, but also the bioaccessible fraction of essential and potentially toxic elements. In this study, the total concentration and bioaccessible fraction of Al, B, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, Ni, V and Zn were evaluated in amaranth, chia and quinoa samples by MIP OES technique. As a method of preparation of samples, acid decomposition with reflux system was used and the parameters sample mass, temperature and decomposition time, and volume of hydrogen peroxide were optimized. For amaranth and quinoa, the most suitable conditions were: 750 mg of sample, 5 mL of HNO3, 2 h of decomposition at 150 °C, followed by the addition of 3 mL of H2O2 and heating for 1 h at 120 °C and for chia: 750 mg of sample, 5 mL of HNO3, 2 h of decomposition at 150 °C, followed by two additions of 2 mL of H2O2 and heating for 1 h at 120 °C, after each addition.The accuracy of the method was evaluated by analyzing the certified reference materials of rice flour (IRMM-804) and tomato leaf (CRM-Agro C1003a), and the recoveries ranged from 82 to 113%. Analyte recovery tests were also performed, and the recoveries obtained ranged from 80 to 118%. In all evaluated pseudocereals, the highest total concentration was found for the macroelements K, Mg and Ca, as well as for the microelements Fe, Mn and Zn, and chia was the sample that presented the highest total concentrations for most elements. When bioaccessibility was evaluated, in general, chia presented the smallest bioaccessible fractions. Among the elements considered essential in our diet, the macromineral that presented the highest percentages of bioaccessible fraction was K (99%) and the micromineral was Cu (59%). In relation to the elements considered potentially toxic, Ba did not exceed 15% of bioaccessible fraction and Al presented concentrations below the detection limit in all samples. The content of phenolic compounds was also evaluated, and Pearson's analysis showed negative correlations between the content of total phenolic compounds and bioaccessibility for most elements in all samples. It was also observed that a high total concentration of B, Ba, Fe, Mn and Zn results in a low bioaccessibility of these elements, depending on the sample. When evaluating the bioaccessible fraction and daily recommendations, Mg was the element that presented the greatest contribution, reaching a maximum value of 19.2%, evidencing the need for additional consumption of other sources of nutrients to achieve the daily requirements of minerals.