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Brazilian Journal of Microbiology

Print version ISSN 1517-8382On-line version ISSN 1678-4405

Braz. J. Microbiol. vol.34  suppl.1 São Paulo Nov. 2003 



Effect of gamma irradiation on the inactivation of aflatoxin B1 and fungal flora in peanut


Efeito da irradiação gama na inativação da aflatoxina B1 e flora fúngica em amendoim



Guilherme PradoI,II; Eliana Pinheiro de CarvalhoII; Marize Silva OliveiraI; Jovita Gazzinelli Cruz MadeiraI; Vanessa Drummond MoraisI; Ricardo Ferracini CorreaIII; Valbert Nascimento CardosoIV; Thaís Veloso SoaresV; Juliana Fonseca Moreira da SilvaV; Rúbia Carolina Pereira GonçalvesV

IDivisão de Vigilância Sanitária, Fundação Ezequiel Dias, Belo Horizonte, MG, Brasil
IIDepartamento de Alimentos, Universidade Federal de Lavras, Lavras, MG, Brasil
IIILaboratório de Medidas Nucleares, Centro de Desenvolvimento de Tecnologia Nuclear, Belo Horizonte, MG, Brasil
IVLaboratório de Radioisótopos, Faculdade de Farmácia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil
VFundação Ezequiel Dias, Belo Horizonte, MG, Brasil





The effect of gamma irradiation on aflatoxin B1 levels and fungal infection were investigated in peanut samples, Tatu Vermelho cultivar. At a radiation dose of 10 KGy, growth of molds was completely inhibited. Doses of 15, 20, 25 and 30 KGy were sufficient for destruction of aflatoxin B1 by 55-74%. The results suggested that the decontamination of molds by irradiation, before production of aflatoxin B1, is the most acceptable method in the preservation of peanut.

Key words: peanut, gamma irradiation, aflatoxin B1.


O efeito da irradiação gama nos níveis de aflatoxina B1 e na infecção fúngica foram investigadas em amostras de amendoim, cultivar Tatu Vermelho. Dose de irradiação gama (60Co) de 10 KGy inibiu completamente o crescimento de fungos. Doses de 15, 20, 25 e 30 KGy foram suficientes para destruição de aflatoxina B1 de 55 a 74%. Pode-se concluir do presente trabalho, que a descontaminação de fungos por irradiação gama antes da produção de aflatoxina B1 é o método apropriado na preservação de amendoim.

Palavras-chave: amendoim, irradiação gama, aflatoxina B1.




Aflatoxins are metabolities of the molds Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius which can grow on a wide variety of agricultural commodities and induce undesirable effects (2).

Different methods have been applied to reduce molds in food, such as fumigation and heat treatment, but none of these methods offers a complete control for toxigenic molds (1).

In september 1997 a Study Group appointed by WHO concluded that "foods treated with doses greater than 10 KGy can be considered safe and nutritionally adequate when produced under established Good Manufacturing Practice" (4,7).

The present study has been conducted to investigate the efficacy of gamma irradiation (60CO) for the decontamination or inactivation of fungi and aflatoxin B1 occurring in peanut, genotype Tatu Vermelho.




The study was carried out analysing three peanut samples (Arachis hypogaea L.) of the Tatu Vermelho cultivar, during the 2003 harvest, of the São Paulo state, Brazil. One sample (A) was naturally contaminated with 248.0 µg/Kg aflatoxin B1 and another (B) with 86.0 µg/Kg aflatoxin B1. In the third sample (C) the aflatoxin B1 was not detected.

Direct Platings

Peanut seeds of the sample C were externally disinfected by immersion in a 0.4% sodium hypochlorite solution for 2 min and then a total of 50 seeds, in four replications, was plated directly (5 particles per plate) onto Dichloran rose bengal chloramphenicol agar (DRBC). The plates were incubated at 25ºC for 5-7 days, then inspected for colony growth visually (8).


Samples A e B were packed into polyethlene pouches and irradiated, in three replications, with doses of 0, 15, 20, 25 and 30 KGy by using 60CO source. Sample C was packed into polyethlene pouches and irradiated, in four replications, with doses of 0, 1, 5 and 10 KGy by using 60CO source, too.

Determination of Aflatoxin B1

A thin layer chromatographic (TLC) method was used for the detection of aflatoxin B1(9).

Statiscal Analysis

The multiple range test described by Duncan (5) was used to test for statistically significant differences (p < 0.05).



The effect of different doses of gamma-irradiation in the percentage infection by fungi is shown in Table 1. The data showed that the percentage infection decreased significantly (p < 0.05) by increasing the radiation dose levels from 5 to 10 KGy and the molds were completely inhibited at irradiation dose of 10 KGy.



Table 2 shows the effect of different doses of gamma-irradiation on aflatoxin B1 levels. The results showed that treatment of peanut seeds with gamma irradiation (15, 20, 25 and 30 KGy) destroyed 69-74% of aflatoxin B1 in sample A and 55-62% in sample B. Farag et al. (6) found that the gamma rays even at 20 KGy were not effective in destroying completely the aflatoxins since 83% reduction was achieved. Recently, Aziz and Youssef (3) showed that a dose of 20 KGy was sufficient for complete destruction of aflatoxin B1 in peanut, yellow corn, wheat and cotton seed meal.




The authors thank the Fundação de Amparo à Pesquisa do Estado de Minas Gerais and CNPq for financial support and the Santa Helena Industry of Foods by the samples of peanut.



1. Aziz, A.N.; Attia, E.S.A.; Farag, S.A. Effect of gamma-irradiation on the natural occurrence of Fusarium mycotoxins in wheat, flour and bread. Nahrung., 41:34-37, 1997.        [ Links ]

2. Aziz, N.H.; Abd El-Rehim, L.M.; El-Far, F.M.A. Effect of gamma-irradiation on aflatoxin B1 produced by Aspergillus parasiticus in barley containing antimicrobial food additives. Egypt. J. Rad. Sci. Applic., 12:101-116, 1999.        [ Links ]

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4. Bruyn, I.N. The application of high dose food irradiation in South Africa. Rad. Phys. Chem., 57:223-225, 2000.        [ Links ]

5. Duncan, B.B. Multiple range and multiple F-tests. Biometrics., 11:1-42, 1955.        [ Links ]

6. Farag, R.S.; Rashed, M.M.; Hussein, A.A.; Abo-Hagar, A. Effect of gamma radiation on the infected yellow corn and peanuts by Aspergillus flavus. Chem. Mikrobiol. Technol. Lebensm., 17:93-98, 1995.         [ Links ]

7. Lara, J.; Fernández, P.S.; Periago, P.M.; Palop, A. Irradiation of spores of Bacillus cereus and Bacillus subtilis with electron beams. Inn. Food Sci. Emerg. Techn., 3:379-384, 2002.        [ Links ]

8. Pitt, J.I.; Hocking, A.D. Fungi and food spoilage. 2nd ed. Blackie Academic and Professional, London, 1997.        [ Links ]

9. Soares, L.M.; Rodriguez-Amaya, D.B. Survey of aflatoxins, ochratoxin A, zearalenone and stergmatocystin in brazilian foods by using mult-toxin thin layer chromatographic methods. J. Assoc. Off. Anal. Chem., 73:22-26, 1989.        [ Links ]



Correspondence to:
Guilherme Prado
Fundação Ezequiel Dias
Rua Conde Tereira Carneiro, 80, Gameleira
30510-010, Belo Horizonte, MG, Brasil



This paper corresponds to an "extended abstract" selected for oral presentation in the 22nd Brazilian Congress of Microbiology, held in Florianópolis, SC, Brazil, in November 17-20, 2003

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