Microbiological and Aflatoxin Evaluation of Brazil Nut Pods and the Effects of Unit Processing Operations

Abstract

Harvesting of Brazil nuts not only helps to preserve the Amazon rainforest but also provides income to individuals who would otherwise have little means of making a livelihood. Recently, the European Community has tightened the quality requirements for Brazil nuts, particularly with regard to aflatoxin levels and microbiological contamination. The objectives of this research were to gain a better understanding of the origin of aflatoxins on Brazil nuts and to microbiologically evaluate some of the operations involved in processing. In this regard, five Brazil nut pods were aseptically picked from trees located in each of three concessions of the Peruvian Amazon rainforest (Madre de Dios province). The exteriors of the pods and the nuts were examined for yeast and molds, including Aspergillus flavus and Aspergillus parasiticus, and for bacteria, including Salmonella and Escherichia coli. Brazil nuts obtained from various commercial process operations located in Peru were similarly evaluated. Exteriors of all Brazil nut pods did not contain A. parasiticus, and only pods from one concession yielded A. flavus isolates. All isolates tested were aflatoxigenic (630 to 915 ppb total aflatoxin). Coliforms, E. coli, and salmonellae were not recovered from any of the pods. Whole, in-shell nuts obtained after opening the pods yielded no A. flavus or A. parasiticus. Aflatoxins were not detected (detection limit 1.75 ppb) in any of the nuts. Whole, in-shell and shelled nuts from various process operations were all positive for A. flavus but negative for E. coli and salmonellae. Soaking of whole, in-shell nuts before cracking or shelling increased coliform numbers, whereas levels of A. flavus decreased. In order to gain a better understanding of the sanitary performance of the unit process operations, additional evaluations should be conducted on product lots processed on different days. Also, the microbiology of product processed from common lots should be followed through the various unit operations and compared.

Factors influencing fungal and aflatoxin levels in Turkish hazelnuts (Corylus avellanaL.) during growth, harvest, drying and storage: A 3-year study

“…Systematic studies on the microflora of fresh nuts are limited, but it appears that A. flavus and A. parasiticus have a particular affinity for nuts and oil seeds (Pitt 2000). A. flavus was the dominant fungi isolated from foodstuffs, defined as the primer producer of aflatoxin with a close relationship to the agricultural environment and crop (Hill et al 1983;Abdel-Hafez and Saber 1993;Abdel-Gawad and Zohri 1993;Bayman et al 2002;S°ims°ek et al 2002;Adebajo and Diyaolu 2003;Arrus et al 2005b). …”

Association between aflatoxin and aflatoxigenic fungi in Brazil nut (Bertholletia excelsa H.B.K.)

“…It is important to emphasize that in unprocessed nuts collected from the forest by Cartaxo et al (2004), those were the predominant strains. In the case of Brazil nut pods collected from the forest by Arrus et al (2005b), the Aspergillus, Penicillium and Fusarium were also detected. Their presence indicated those as an original contamination, and not only associated with inadequate storage at the markets, observed in the retail samples.…”

Brazil nut sorting for aflatoxin prevention: a comparison between automatic and manual shelling methods

“…This can be explained by the use of diferente batches, containing nuts of different origins and different characteristics, during the various stages of processing since the temperatures used should decrease proportionally with the decrease in mc and aw. According to Arrus et al, (2005a), despite the accuracy of the aw meter (70.01%), the variation between these values could have resulted in slight differences in mc beween the nuts, which were kept under controlled RH since different nuts were used to determine mc and aw. Such process can also cause changes in the chemical composition of the nutrients present in the nuts or physical defects (e.g.…”