Evaluation of viability of Aspergillus flavus and aflatoxins degradation in irradiated samples of pistachio

S.A. Yazdanparast1, M. Barzegar 2, F. Saeedi 2

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Background: One of the currently most important fungi in stored grains is Aspergillus flavus which produce aflatoxins. Therefore, the study of techniques that can be applied to the control of aflatoxins is of great importance. The objective of the present study was to determine the effects of gamma radiation on the growth of A. flavus Link and on degradation of aflatoxin B1 and B2 at a relative humidity of 97- 99% and a water activity (Aw) of 0.88-0.94. Materials and Method: 20 samples of pistachios grown in Pirassununga/SP were individually packaged and irradiated with 20 kGy, using a 60Co gamma ray facility to eliminate the natural microbial contamination. All samples were used for Aw determination; plate counting, fluorescent viability test and aflatoxin analysis.100 grams (50 g) samples were grounded and thoroughly mixed with 450 mL of sterile distilled water. 25 grams of each sample were extracted with methanol/4% KCL. The extracts were clarified with 30% ammonium sulfate solution and then the aflatoxins were extracted by adding chloroform. Identification and quantification was conducted via thin layer chromatography by comparison with standards. Result: Results have shown that irradiation effectively reduces the number of CFU in the samples under investigation at all doses used, but the effect was more dominant at higher irradiation doses which is in accordance to the data shown by Rustom, that reported the reduction of fungal growth increased with increasing irradiation doses. Conclusion: Humidity, free water and temperature of substrate and the combination with low doses of irradiation, to lead a good result in a fungal control. The obtained results with the fluorescent method, in front of growth and plate count of colonies, showed consonance between these techniques, revealing a efficient effect of gamma radiation, observed in the decrease of viable cells number with the raise of irradiation doses. Keywords: Aspergillus flavus, Aflatoxin, pistachio

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Iranian Congress on Medical Mycology
    • ICMM 2011