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

MICOTOXINS

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 Prado^I,II; Eliana Pinheiro de Carvalho^II; Marize Silva Oliveira^I; Jovita Gazzinelli Cruz Madeira^I; Vanessa Drummond Morais^I; Ricardo Ferracini Correa^III; Valbert Nascimento Cardoso^IV; Thaís Veloso Soares^V; Juliana Fonseca Moreira da Silva^V; Rúbia Carolina Pereira Gonçalves^V

^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

^{Correspondence}

ABSTRACT

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.

RESUMO

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.

INTRODUCTION

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.

MATERIALS AND METHODS

Sampling

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).

Gamma-Irradiation

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).

RESULTS AND DISCUSSION

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.

ACKNOWLEDGEMENTS

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.

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

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Publication Dates

• Publication in this collection
  29 Nov 2004
• Date of issue
  Nov 2003