ABSTRACT
Sorghum, which is consumed in Tunisia as human food, suffers from severe colonization by several toxigenic fungi and contamination by mycotoxins. The Tunisian climate is characterized by high temperature and humidity that stimulates mold proliferation and mycotoxin accumulation in foodstuffs. This study investigated the effects of temperature (15, 25 and 37 °C), water activity (a w, between 0.85 and 0.99) and incubation time (7, 14, 21 and 28 d) on fungal growth and aflatoxin B1 (AFB1) production by three Aspergillus flavus isolates (8, 10 and 14) inoculated on sorghum grains. The Baranyi model was applied to identify the limits of growth and mycotoxin production. Maximum diameter growth rates were observed at 0.99 a w at 37 °C for two of the isolates. The minimum a w needed for mycelial growth was 0.91 at 25 and 37 °C. At 15 °C, only isolate 8 grew at 0.99 a w. Aflatoxin B1 accumulation could be avoided by storing sorghum at low water activity levels (≤0.91 a w). Aflatoxin production was not observed at 15 °C. This is the first work on the effects of water activity and temperature on A. flavus growth and AFB1 production by A. flavus isolates on sorghum grains.
El sorgo, que se consume en Túnez como alimento humano, puede sufrir la colonización severa de varios hongos toxicogénicos, con la consiguiente bioacumulación de micotoxinas. Además, el clima de Túnez, caracterizado por las altas temperaturas y humedad, estimula el crecimiento fúngico y la acumulación de micotoxinas en los productos alimenticios. Este estudio investigó los efectos de la temperatura (15, 25 y 37 °C), la actividad de agua (a w) (entre 0,85 y 0,99) y el tiempo de incubación (7, 14, 21 y 28 días) sobre el crecimiento y la producción de aflatoxina B1 (AFB1) de 3 aislados de Aspergillus flavus (designados como 8, 10 y 14) que se inocularon sobre granos de sorgo. El modelo Baranyi se aplicó para identificar los límites del crecimiento y la producción de micotoxinas. Las tasas máximas de crecimiento para 2 de los aislados se observaron en la combinación 0,99 a w y 37 °C. La a w mínima necesaria para el crecimiento del micelio fue de 0,91 a 25 °C y 37 °C. A 15 °C, solo el aislado 8 creció a 0,99 a w, pero fue incapaz de producir la aflatoxina B1. Es posible evitar la acumulación de aflatoxina B1 en el sorgo almacenándolo a baja actividad de agua (≤ 0,91 a w). Este es el primer trabajo que ha estudiado el efecto de la actividad del agua y la temperatura sobre el crecimiento de aislados de A. flavus y su producción de aflatoxina B1 en granos de sorgo.
Subject(s)
Aspergillus flavus/growth & development , Aflatoxin B1/isolation & purification , Aflatoxin B1/analysis , Humidity/adverse effects , Mycotoxins/analysis , Temperature , Sorghum/microbiology , Sorghum/toxicityABSTRACT
Descreve-se um surto de intoxicação espontânea por Sorghum sudanense (aveia de verão, capim-sudão) em um rebanho de bovinos leiteiros no município de Triunfo, Rio Grande do Sul. Essa planta é utilizada como forrageira em diversas regiões do estado; entretanto, intoxicações ocasionais são associadas com a formação de ácido cianídrico por hidrólise dos glicosídeos cianogênicos presentes na planta. Vinte e nove vacas Holandesas foram colocadas, no final do dia, em um potreiro de 800m², onde uma pastagem estabelecida de capim-sudão rebrotava e atingia 30cm de altura. Na manhã seguinte, quase todo pasto havia sido consumido e três vacas foram encontradas mortas. Não foram relatados sinais clínicos, mesmo porque os animais não foram observados durante a noite. Exceto pela presença de folhas mastigadas de capim-sudão nas proximidades da entrada do rúmen, não foram observadas alterações macro ou microssópicas. Amostras da planta de diferentes locais no potreiro foram positivas no teste do papel picrossódico. Esses achados sugerem que as três vacas foram afetadas por intoxicação cianídrica secundária ao consumo de Sorghum sudanense.
An outbreak of Sorghum sudanense (Sudan grass) poisoning affected three cows from a dairy herd in Triunfo, Rio Grande do Sul, Brazil. Although S. sudanense has been used as a source of forage for cattle, sporadic poisoning occurs in association with management failures of these pastures. Cyanogenic glycosides present in the plant may form hydrogen cyanide through hydrolysis and may cause livestock poisoning. Twenty-nine Holstein cattle were allowed to graze in an 800m² paddock, in which lush sprouts of sudanense were 30cm high. Animals were placed on pasture at evening and, in the next morning, most forage had been consumed and three cattle were found dead. No clinical disease was noticed. Except by the presence of chewed sudan grass leaves near to the entrance of the rumen, there were neither macroscopic nor microscopic changes, Samples of S. sudanense taken from different places in the paddock were positive when evaluated by the picrosodic paper test. Such findings suggested that those three cows were affected by cyanide poisoning secondary to Sorghum sudanense consumption.