Desenvolvimento de métodos para análise qualitativa e quantitativa de aflatoxinas em amendoim.

Abstract

Fungi species of Aspergillus are the main contaminants of seeds and peanuts in storage conditions. These fungi grow produce aflatoxins are secondary metabolites of high toxicity. The difficulty of detection and quantification of aflatoxins directly in the sample is a limiting factor in many areas of study and also the industry. With technological advances, new methods have been proposed to overcome this problem. The diffuse reflectance spectroscopy of the visible (VIS) and near infrared (NIR) occupies a prominent place not require sample preparation and advantages of nondestructive and rapid. The objective of this work was to study the incidence of A. parasiticus and aflatoxin levels in peanuts stored using reflectance measurements of 400 to 2500 nm. The kernels were previously irradiated with 60Co to 25 kGy and inoculated with toxigenic strain of A. parasiticus concentration of 3.0 x 106 spores / g of kaolin powder. A total of 36 samples with 200 g each were divided into 3 blocks. To simulate the ideal conditions to produce aflatoxins, samples with 11% moisture contend were stored inside the incubator chamber at 30 °C, 12 h photoperiod and relative humidity of 85% for 16 days. Every two days of incubation was held health test, determining the moisture content of grain, record the spectra in the region of 400 to 2500 nm in the whole grain and ground detection and quantification of aflatoxins by DCC. Aflatoxins were detected in all samples inoculated at a concentration range from 180 to 730,000 mg kg"1. The spectra were pre-processed by algorithm Savitzy-Golay first derivative, second-order polynomial and a window of 21 points. Models for the identification of aflatoxins in grains and crushed material were based on PCA spectra derivative. The explained variance was above 98% for three PCs in identifying treatments infected with A. parasiticus and the presence of aflatoxins. The PLS models for total aflatoxins provided correlation coefficients and RMSEP of 0.9827 and 5.2 x 104 g kg"1 for the VIS region and 0.9540 x 104 and 8.5 mg kg"1 for the NIR. The concentration of aflatoxins was three times higher than the limit of ANVISA the sixth day of incubation. The VISNIR spectroscopy with PCA and PLS allowed a rapid and non-destructive classification of contaminated samples and quantification of aflatoxins in peanut kernels artificially contaminated with A. parasiticus.