Desenvolvimento de Métodos Analíticos para Determinação Elementar e Fração Bioacessível em Cogumelos Comestíveis por MIP OES

Abstract

Varied species of mushrooms are consumed worldwide, among these, the most consumed are: Agaricus bisporus, Pleurotus ostreatus and Lentinula edodes. Considering that these foods are characterized by the bioaccumulation of different compounds, depending on the concentration present in the culture medium, it is essential to monitored the elemental composition, in order to evaluate the presence of essential and potentially toxic elements to human health. For this study, the acid decomposition conditions were optimized the using reflux system, through a multivariate design, being evaluated the independent variables: sample mass, temperature, time of decomposition and volume of H2O2. For this experimental design, the volume of HNO3 was kept fixed at 5 mL and the time of 1 h after the addition of H2O2. Thus, it was obtained as an optimal condition for the elements Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Pb and Zn, the conditions of: 500 mg of sample mass, 125 °C of temperature, 120 min for decomposition time and 2 mL for the volume of H2O2. Using the microwave-induced plasma optical emission spectrometry (MIP OES) technique was used for analyte determinations. The accuracy of the method was evaluated using certified reference materials of sugar cane (CRM-Agro C1005a) and tomato pulp (CRM-Agro C1004a), also with the addition of these materials at the sample and analyte addition tests. All recoveries were in the range of 80 and 120 %. The method was applied to 21 samples of three different species sold in the city of Pelotas/RS. The concentration range obtained was 0.19 to 10.03 mg kg-1 for Al; 2.84 to 60.64 mg kg-1 for Ca; 0.43 to 7.13 mg kg-1 for Cu; 2.05 to 26.1 mg kg-1 for Fe; 1,195 to 4,005 mg kg-1 for K; 69 to 174 mg kg-1 for Mg; 0.415 to 2.4 mg kg-1 for Mn; 9.6 to 165 for Na; 0.208 to 0.69 mg kg-1 for Pb and 2 to 11.85 mg kg-1 for Zn. For Ba, Cd and Cr all the found values in the samples were below the detection limits, which is 0.0014; 0.012 and 0.0016 mg kg-1, respectively. For the bioaccessible fraction, the % in relation to the total concentration ranged from 1 to 53 % for Al; 0 to 87 % for Cu; 0 to 79 % for Fe; 59 to 95 % for K; 42 to 82 % for Mg; 7 to 84 % for Mn; 41 to 74 % for Pb and 20 to 55 % for Zn. From this, it can be seen that the method developed presented satisfactory results through validation studies. The concentrations in the different samples showed a great variation in the total concentration and bioaccessible percentages, demonstrating the importance of nutritional information of edible mushrooms. The studied samples presented essential elements, in addition to concentrations for Pb, which is a potentially toxic element, which was above the recommended by the legislation for practically all the studied samples.