Temperature, Relative Humidity and Incubation Period as Critical Factors in Aspergillus Flavus Growth and Aflatoxin B1 Production on Maize Grains
Abstract
Maize, an important staple in Nigeria and a major feed ingredient in the poultry industry is prone to aflatoxin B1 contamination as a result of favourable environmental and storage conditions that promote the growth of Aspergillus flavus from which aflatoxin B1 evolves. This study was conducted to assess the effect of storage conditions (temperature and relative humidity) and incubation period (14 and 21 days) on the growth of Aspergillus flavus and subsequent aflatoxin B1 production on maize. In a completely randomized design, 40 kilograms of pure maize were divided into 4 treatments (T1 to T4) of 10 kg each while each treatment was again replicated twice. Treatment 1 was the control which is the maize that was not inoculated with fungi and kept in a well-ventilated room (average temperature and humidity of 260C and 60% respectively). Treatments 2, 3 and 4 respectively contained maize that were inoculated with a pure strain of Aspergillus flavus but kept under the shed (average temperature and humidity of 330C and 58% respectively), refrigerator (average temperature and humidity of 140C and 65% respectively), and in the open air (average temperature and humidity of 320C and 75% respectively). The maize was left to incubate for 14 and 21 days. The result of Aflatoxin B1 levels from T1 to T4 after 14 days showed significant (p<0/05) difference in mean values for samples that were kept for 14 days (0.00, 20,856.50, 19,342.50 and 28,191.00 ppb) with the highest value recorded in Treatment 4 that were incubated in the open air. In sharp contrast to this, maize that was incubated for 21 days recorded significant differences in their mean values (0.00, 19,487, 481 and 12,253 ppb) from T1 to T4 but those incubated in the open air recorded lower aflatoxin B1 values (12,253 ppb) compared to the one under the shed (19,487.00 ppb). No aflatoxin was recorded in the control treatment. In conclusion, a temperature as low as 140C will favour mould growth and aflatoxin production within a period not longer than 2 weeks. Also, more aflatoxin is produced in maize that is left in the open air or in the field where temperature and relative humidity are higher than under the shed or refrigerator which provides a cooler environment.
Downloads
References
Diener, U.L. and Davis, N.D. (1967). Limiting temperature and relative humidity for growth and production of aflatoxin and free fatty acids by Aspergillus flavus in sterile peanuts. J. Am. Oil Chem. Soc. 44(4):259-263.
Dix, N.J. and Wester, J. (1995). Fungi of extreme environments. Fungal Ecology. Dordrecht: Springer Netherlands, 322.
Dutta, T.K., and Das, P.I. (2001). Isolation of aflatoxigenic strains of Aspergillus and detection of aflatoxin B1 from feeds in India. Mycopathologia 151:29-33.
FAO (Food and Agricultural Organization), (2007). On farm mycotoxin control in food and feed grain. Available from: http://faostat.fao.org/3/a1416e/a1416e.pdf.
FAO (2003). Food and Agricultural Organization http://faostat.fao.org/default.htm
Gugnani, H.C., (2000). Ecology and taxonomy of pathogenic aspergillus. Front Biosci, 8:346-57
Lahouar, A., Crespo-Sempere, A., Marin, S., Said, S. and Sanchis, V. (2015). Toxigenic moulds in Tunisian and Egyptian sorghum for human consumption. Journal of stored products Res., 63:57-62
Shotwell, O., Hesseltine, L. C. W., Stubblefield, R. D. (1966). Production of aflatoxin on rice. Appl. Microbiol. 15:425-430.
Suhagia, B.N., Shayiq, S.Q., Rathod, I.S., and Patel, H.M. (2006). Determination of Azithromycin in pharmaceutical dosage forms by spectrophotometric method. Indian Journal of Pharmaceutical Sciences. 68(2):
Schindler, A.F., Palmer, J.G. and Eisenenberg, W.V. (1967). Aspergillus flavus as related to various temperatures. Appl Microbiology. 15(4):945-9
