V. de S. Álvares

Incidence of Aspergillus flavus, Aspergillus parasiticus and aflatoxins in Brazil nuts in the Amazon forest environment

This work aimed to evaluate, in the Amazon Forest environment, the effect of time on contamination of Brazil nuts with Aspergillus flavus, Aspergillus parasiticus and aflatoxins after falling of the pods. Samples were collected at three different times and analysed for water activity, potentially aflatoxigenic fungi A. flavus and A. parasiticus, other fungi and aflatoxins. The mean values for the parameters tested were: water activity 0.98; A. flavus and A. parasiticus 1.3×101 colony forming units (cfu)/g; other fungi 3.2×103 cfu/g; aflatoxin B1 0.073 μg/kg, aflatoxin B2 0.009 μg/kg, aflatoxin G1 0.034 μg/kg and aflatoxin G2 0.007 μg/kg. The incidence of A. flavus and A. parasiticus was not significantly affected by the time, during which the pods were on the forest soil. Moreover, aflatoxins levels were low during the whole study period, suggesting that adverse forest conditions were not the main factor that stimulate the production of aflatoxins.

Quality of in-shell Brazil nuts after drying using a pilot natural convection oven in the state of Acre, Brazil

The natural drying of in-shell Brazil nuts carried out by the extractivists is not effective in reducing contamination by aflatoxin-producing fungi. Thus the use of an artificial heater could prove to be a favourable method to bring about a rapid reduction in the moisture content of the nuts and thereby prevent fungal growth. Hence the objective of this study was to evaluate the efficiency of a natural convection-type drier with respect to the physical, physicochemical and microbiological quality of nuts after drying for 6 hours at 45 °C. A random block experimental design with two treatments (nuts before and after drying) was used, using 10 replications of 3 kg. The nuts were analysed for their moisture, ash, protein, dietary fibre, total carbohydrates and lipid contents, water activity, total count of filamentous, potentially aflatoxin-producing fungi, and also the quantification of aflatoxins B1, B2, G1, G2 and the total aflatoxins. There was no effect of drying on the Aspergillus flavus and Aspergillus parasiticus counts or on the physicochemical composition of the nuts, except for the ash content. However the moisture content of the nuts was reduced by 39.7% and there was a decrease in the contamination by pre-existing total filamentous fungi. The dryer was effective in reducing the average time taken for drying as compared to the traditional method used by extractivists.