Micotoxinas em matrizes de milho e trigo: validação de método analítico por ULPC-MS/MS e monitoramento em diferentes pontos da cadeia produtiva e comercial

Abstract

This study aims to validate an analytical multi-mycotoxin method using UPLC-MS/MS for 12 mycotoxins determination in wheat and maize matrices. The parameters evaluated for the validation were: calibration curve and linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy (recovery%), precision (RSD %) and matrix effect. The extraction of mycotoxins was performed using the modified QuEChERS method, whereby were used 12.5 g of slurry (suspension between sample and water), 4.5 g MgSO4 anhydrous and 10 ml of acidified acetonitrile at 1% acetic acid. After method validation, it was used to search, quantitatively, the occurrence of mycotoxins in 646 samples, 476 samples of wheat (the field trials, exported and imported grain type, grain processing and their fractions (flour and bran) and flour collected in supermarkets) and 170 samples of maize (grain exported type, flour collected in supermarkets, grains and brewer for the manufacture of animal feed). The results were satisfactory for all evaluated parameters, thus showing that the method validated for the matrices of wheat and maize, it is effective to determine these 12 mycotoxins studied. The matrix effect for some mycotoxins was outside the range -20 to +20%. These results for some analytes were compensated by matrix-mached calibration. All were contaminated by at least one of 12 mycotoxins in the study, regardless of origin. The mycotoxin DON was predominantly found in wheat samples, while fumonisin were determined in maize. In the field trials, factors such as genotype, environment and fungicide treatment had influence on DON concentration. Wheat grain for exportation and imported from Argentina had DON contamination in all samples. In wheat for exportation, also been determined contamination for FB1, FB2, ZEN and OTA. There is evidence that this is the first study to report the presence of fumonisins in Brazilian wheat, since it was not found other reports in the literature. In the sub-products of milling was observed redistribution of DON, a decreased concentration in white flour and increased in bran fraction when compared to the initial concentration in the grain, showing that this process is not effective for mycotoxins removal. It was determined DON and ZEN mycotoxins in flour samples purchased either in the city of Cruz Alta as Santa Maria as well. In maize samples for exportation was observed concomitant contamination by DON, ZEN, FB1 and FB2 and AFLA B1. In maize flour samples collected from supermarkets all samples were contaminated with fumonisins. Besides fumonisins evidenced the presence of DON, ZEN and AFLA B1 in some samples. Samples destined for the production of animal feed were determineted with aflatoxins (B1, B2, G1, G2), fumonisins (B1 and B2), DON and ZEN, and in some samples, the concentrations were higher than Brazilian MRL. The extraction method combined with modern chromatographic technique for the determination of analytes, were effective for the analysis of mycotoxins in wheat and maize. Even in concentrations below the legal limits, human been exposure to mycotoxins can occur constantly. Monitoring of mycotoxins in foods is extremely important for public health, seeking quality to make healthy products available at all points of the supply and commercial chain.