RESUMO
It has been demonstrated in several agricultural regions all around the world that Aspergillus flavus can infect corn grains and produce aflatoxins even before the harvest. It is also known that the incidence and levels of contamination of cereals factors. In the present work, the incidence of aflatoxins in corn grain from the central and northern areas of Santa Fe province in Argentina was studied. The relationship between the extent of kernel infection by the fungus and the presence of aflatoxins in the samples was examined. The isolation and identification of A.flavus were carried out by plating dilutions of the ground kernels on dichloran-rose bengal-chloramphenicol agar (DRBC). Simultaneously, kernels were superficially sterilized with 10% commercial CIONa and plated on potato-dextrose-chloramphenicol agar (PDA + C). The analysis of aflatoxins B1, B2, G1 and G2 was performed by thin layer chromatography (TLC) according with Norma IRAM 14803 (Argentina). A.flavus Link:Fr. was identified in 63.3% of the corn samples. Colonized kernels ranged from 2.5 to 25% and counts on DRBC were in the order of 10(3) CFU/g. Two samples colonized by A.flavus contained aflatoxins B1 and B2 (50 micrograms/kg of aflatoxin B1 and 30 micrograms/kg of aflatoxin B2, and 30 micrograms/kg of aflatoxin B1, and traces of aflatoxin B2, respectively). One sample contained only aflatoxin B1 (22 mu/kg). According to these results, it may be concluded that the incidence of A.flavus observed constitutes a call in attention with respect to the conditions required for storage and transportation of the grains, to minimize the proliferation of the fungus and the production of aflatoxins in these stages. Although the incidence of aflatoxins in the samples of grains was rather low, the levels of aflatoxin B1 recorded in the positive samples were higher than those recommended--or given as advisory levels for human foods, by most countries in the world.
Assuntos
Aflatoxinas/isolamento & purificação , Aspergillus flavus/isolamento & purificação , Grão Comestível/química , Grão Comestível/microbiologia , ArgentinaRESUMO
En muestras de granos de maíz de la zona centro norte de la Provincia de Santa Fe, Argentina, se seleccionaron 10 cepas de Aspergillus flavus, para estudiar sus características morfotaxonómicas y toxicogénicas. Para los ensayos taxonómicos se efectuaron observaciones macro y microscópicas de los cultivos puros en CYA y MEA, mientras los ensayos de toxicidad en el medio YES, registrandose la producción de aflatoxina en algunas cepas a los 7, 14 y 21 días de incubación. Mediante el empleo de cromatografía en capa fina, se determinó la presencia de aflatoxinas con los estandares correspondientes (B1, B2, G1, G2). Los resultados obtenidos en base a la morfología y a la producción de aflatoxinas, permitió afirmar que la totalidad de las cepas ensayadas, pertenecían a las especie A.flavus Link:Fr. Dos cepas produjeron aflatoxinas B1 y B2, a los 14 y 21 días de incubación. Solo 1 de ellas produjo cantidades significativas de ambas toxinas, pero ninguna produjo aflatoxinas G. Se destaca el valor quimiotaxonómico de los estudios de toxigenicidad, para la identificación a nivel de especie dentro de la sección Flavi
Assuntos
Aspergillus flavus/patogenicidade , Zea mays/parasitologia , Aflatoxinas/isolamento & purificação , ArgentinaRESUMO
The incidence of Fusarium toxins-trichothecenes and zearalenone in 100 samples of whole grains as well as their distribution in the by-products (arising of 32 whole corn samples) of the wet-grinding of corn were studied, the samples coming from the central and northern areas of the Santa Fe Province, Argentina. The analyses were carried out by thin-layer chromatography. A 33% of the samples was found to be contaminated by deoxynivalenol (DON), its amount ranging from traces to 1,200 micrograms/Kg; 15% of the samples contained T-2 toxin from 900 to 2,400 micrograms/Kg and only traces of zearalenone were detected in one sample. Only few samples (7%) included diacetoxiscirpenol (DAS), nivaleno (NIV) and neosolaniol (NS) and 7% of the samples evidenced contamination by more than one mycotoxin. It is worth noticing that DON was found to be contaminating only those by-products destined to human consumption. Conversely, T-2 toxin was found in by-products destined to both human and animal consumption.
