Effect of Ozone Gas on Brazil Nut( Bertholletia excelsa H. B. K. ) Mycoflora and Aflatoxin Reduction

摘要

Raw Brazil nuts grow and are harvested in the wild of the Amazon forest. At postharvest they are submitted to two storage stages prior to their drying process. The first storage is in the forest(on pallets)and the second in cities near the Amazon River or its tributaries to be subsequently send to the factories by boat. They are kept in wooden silos inside suspended stalls to keep them away from the environment. Despite of that, the relative forest humidity and temperature are high and suitable to fungi proliferation. The main biological factor that can affect inshell nuts' quality during storage is fungi （deteriorating and aflatoxigenic strains) apart from forest termites. This work reports on an evaluation of ozone（O3)gas influence on Brazil nut fungi load and its effect on aflatoxins(AFLs). Groups of inshell Brazil nuts(14kg) from the year 2006 harvest,AFL contaminated with 5.62（g/kg,collected in the Brazilian Amazon were submitted to O3 treatment at different concentrations and conditions. After the gas exposure period,nuts were submitted to mycology tests,moisture and AFL analysis. Total fungi count was carried out utilizing malt extract agar and the aflatoxigenic fungi identification with A.flavus and Parasiticus agar. The nuts' moisture was determined by gravimetry and AFB1 by high performance liquid chromatography with fluorescencedetection. As expected, the mycological tests showed that O3 treatment affected mycoflora growth, lowering their efu/g count and so the moisture content（from 8.2% to 5.6 %). The O3treatment applied within 5 hours at 31 mg/L was able to successfully destroy nuts'fungi contamination(initial efu/g:40 x 104). Fungi reduction just after harvesting by applying O3 will certainly reduce the possibility of further fungi proliferation and so AFL formation. From a food quality and safety point of view, prevention is a better strategy than detoxification which is much more complicated and so are the implications towards human and animal health.