Efficacy of sodium hypochlorite and peracetic acid against Aspergillus nomius in Brazil nuts

Abstract

The objective of this work was to assess the efficacy of sodium hypochlorite and peracetic acid for sanitization of Brazil nuts. To evaluate the natural microbiota of the nuts, the total bacteria and fungi as well as the Aspergillus section Flavi were counted. The moisture, water activity and the presence of aflatoxins was quantified. The response surface method was used to determine the influence of exposure time and sanitizers concentration on the reduction of Aspergillus nomius inoculated on the nuts. Microbiological, sensory and quantification analyzes of aflatoxins were performed under optimum conditions The evaluation of the initial contamination of the nuts, despite presenting high microbiological contamination, humidity and water activity, was not detected aflatoxins in any samples. In artificially inoculated samples, the response surface and the desirability function were obtained to determine the optimal point of use for each sanitizer. The nuts had high microbiological contamination, moisture content and water activity. Aflatoxins were not detected in any samples. The response surface and desirability function indicated the optimal sanitization conditions were 250 mg/L and 8.5 min and 140 mg/L and 15 min for sodium hypochlorite and peracetic acid, respectively. Reductions greater than 2 log CFU/g were obtained with sodium hypochlorite and of 1 log CFU/g for peracetic acid. In the tests performed with new Brazil nuts samples under the optimized conditions, reductions of less than 2 log CFU/g were obtained. Aflatoxin B1 was detected in one untreated sample (1.51 μg/kg), one sample treated with sodium hypochlorite (0.60 μg/kg) and two samples treated with peracetic acid (0.64 and 0.72 μg/kg). Demonstrating that the sanitizers in the concentrations used had no action on aflatoxins, despite being efficient for fungal control. The treatments did not cause an unacceptable sensorial impact on the samples.