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Andersson, Ellinor, 2012. A small growth study of Aspergillus section Flavi, and potentially aflatoxigenic fungi and aflatoxin occurrence in Brazil nuts from local markets in Manaus, Brazil. First cycle, G2E. Uppsala: SLU, Dept. of Microbiology

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Abstract

This study aimed to gain more knowledge about morphological features of eight different species of Aspergillus section Flavi, which may aid in identification of these species. The presence of potentially toxigenic Aspergillus section Flavi, and occurrence of aflatoxins, in ready-to-eat Brazil nuts (Bertholletia excelsa) were also investigated.

Seventeen different strains, representing eight species from section Flavi, were grown at different water activities and different temperatures. After 7 days, as well as at 14 and 28 days for the lower water activities, colonies were visually inspected, and diameter and macroscopic characteristics were noted. Ten samples of Brazil nuts were collected from different market stalls in the city of Manaus, Brazil. Aspergillus section Flavi were isolated and identified by morphology and toxin profile. Toxin production was evaluated by the agar plug technique and quantification of aflatoxins in the Brazil nuts was performed by high-performance liquid chromatography.

It was found that macromorphology can be used to differentiate between some of the species if the different methods were combined, but for more certain identification, other available methods are better. One hundred and thirty five strains of suspected Aspergillus section Flavi were isolated and aflatoxin production was observed in 100 of them (74%). The most common species was Aspergillus nomius, followed by A. flavus and A. tamarii. Total aflatoxin content detected in the nuts did not exceed the European legislative limit of 10 µg/kg for ready-to-eat Brazil nuts, which would be considered safe to be consumed.

Main title:A small growth study of Aspergillus section Flavi, and potentially aflatoxigenic fungi and aflatoxin occurrence in Brazil nuts from local markets in Manaus, Brazil
Authors:Andersson, Ellinor
Supervisor:Leong, Su-lin and Taniwaki, Marta
Examiner:Passoth, Volkmar
Series:Examensarbete / Sveriges lantbruksuniversitet, Institutionen för mikrobiologi
Volume/Sequential designation:2012:13
Year of Publication:2012
Level and depth descriptor:First cycle, G2E
Student's programme affiliation:NK003 Mat & hälsa - kandidatprogram 180 HEC
Department:(NL, NJ) > Dept. of Microbiology
Keywords:Aspergillus section Flavi, Aflatoxin, Brazil nut, mould growth, Brazil, morphological identification
URN:NBN:urn:nbn:se:slu:epsilon-s-1782
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-s-1782
Subjects:Food contamination and toxicology
Language:English
Deposited On:18 Oct 2012 14:25
Metadata Last Modified:18 Oct 2012 14:25

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