Avaliação da presença de fungos e micotoxinas na tecnologia de pós-colheita do milho

AUTOR(ES)

Marcelo da Silva

DATA DE PUBLICAÇÃO

2007

RESUMO

Corn is an important cereal crop in Brazil as a major ingredient of animal feed and as raw material included in more than 500 cereal based products. Nevertheless, due to its nutritional quality it becomes an excellent substratum for the toxigenic fungi contamination. In order to evaluate the effect of the time interval between the harvesting and the pre-drying step on the fungal and fumonisin contamination, 490 samples were collected in three points of the corn producing chain, field (n=100), delivery post (reception) of the cooperative (n=100) and pre-drying step (n=45) from two consecutive crops (2003 and 2004) of the North Region of Paraná State. The two crops showed a similar profile concerning the fungal frequency. Fusarium sp. was the prevalent genera (100%) for the three sampling sites from both crops, followed by Penicillium sp. which was detected in 98%, 95% and 97% of samples from field, reception and pre-drying step (2003 crop), respectively. Fumonisins were detected in all samples from the three points of producing chain belonging to both 2003 and 2004 crops. Fumonisin levels ranged from 0.11 to 15.32 µ^g/g in field samples, from 0.16 to 15.90 µ•g/g in reception samples and from 0.02 to 18.78 µ•g/g in pre-drying samples belonging to 2003 crop. Samples from 2004 crop showed lower contamination and fumonisin levels ranged from 0.07 to 4.78 µÅg/g in field samples, from 0.03 to 4.09 µëg/g in reception samples and from 0.11 to 11.21 µëg/g in pre-drying samples. The mean fumonisin levels increased gradually from =5.0 g/g to 18.78 µ1g/g as the time interval between the harvesting and the pre-drying step increased from 3.2 to 8.9 hours (2003 crop). The same profile was observed for samples from 2004 crop. Fumonisin levels and the time interval (=0.96) showed positive correlation (p <0.05), suggesting that delay in drying process can increase fumonisin levels in corn. In addition, corn quality concerning to fungal and fumonisin contamination was evaluated in 870 freshly harvested corn samples (2003 and 2004) used as raw material by corn processing industries in the North region of Paraná State. Sampling was carried out in two points of corn producing chain, i.e., reception of processing industry (n=300) and pre-drying step (n=135) for each crop. Corn samples were frequently contaminated with Fusarium sp. (100%) and Penicillium sp. (90 to 95%), when compared to Aspergillus sp. (6 to 15%). Fumonisin B1 (FB1) was detected in all samples from the two points of corn producing chain belonging to both crops. FB1 levels ranged from 0.02 to 11.83 mg/g in reception samples and from 0.02 to 10.98 mg/g in pre-drying samples belonging to 2003 crop. Samples from 2004 crop showed FB1 levels ranging from 0.03 to 12.04 mg/g in reception samples and from 0.06 to 7.74 mg/g in pre-drying samples. FB2 levels ranged from 0.02 to 5.25 mg/g in reception samples and from 0.01 to 7.89 mg/g in pre-drying samples (2003 crop), while in samples from 2004 crop FB2 levels ranged from 0.02 to 6.12 mg/g in reception samples and from 0.05 to 3.47 mg/g in pre-drying samples. Considering 4.0 µdg/g as the maximum fumonisin level recommended for pasta production, 351 samples (80.7%) from 2003 crop and 430 samples (98.8 %) from 2004 crop were safe for human consumption. Low fumonisin levels were detected in the most corn samples used as raw material by processing industries in the North region of Paraná State. Nevertheless, constant monitoring control regarding the throughout corn producing chain is essential for hazard minimization and compliance with trade requirements. Parallely, fluorescence point counting, thin layer chromatography (TLC) and spectrofluorimetry were compared through analysis of 40 naturally contaminated corn samples and positive for Aspergillus flavus group. Aflatoxins were detected by TLC in 16 (40%) samples, while 24 (60%) samples were positive by spectrofluorimetry. Data obtained by TLC and spectrofluorimetry showed a good correlation (r=0,97). Analysis by fluorescence point counting showed 20% of falsenegative results, suggesting its application on screening of sample lots possibly contaminated by aflatoxins.

ASSUNTO(S)

alimentos - biotecnologia micotoxinas milho aflatoxina biotecnologia agrícola agricultural biotechnology aflatoxins mycotoxins corn food - biotecnology

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