Identificação e caracterização de fungos toxigênicos associados à farinha de mandioca (Manihot sp.) / Teresa Alarcon Castillo.

Dissertação (mestre) - Universidade Federal do Amazonas, 2004

Toxygenic moulds are spreading worldwide, they grow in different substracta and in adequated conditions of humidity, pH and temperature. They must be anlyzed not only for the negative impact caused by the product deterioration but also for the problems that may cause to humans and others animals. This research has an objective to make inventory of the mycobiotic toxigenic, the extracellular compounds production by moulds in cassava flour (Manihot sp), and verify mycological quality of the flours after thermal treatment. In order ro evaluate the presence of moulds in cassava flour, we obtained 36 flours samples in supermarkets of greatest competition in the city of Manaus-AM. To evaluate presence of moulds it was used successive dilution technique, inoculation 0,2mL dilution 10³ onto Sabouraud and Czapek agar, added of clorafenicol 0,05g/L and Rose of Flare 0,025%.The detection of secondary metabolites with characteristics of mycotoxins was carried on solid medium (YES) and on thin layer chromatography (CCD). From the analyzed samples, 13,5x10³ UFC in Czapek agar and 14,5x10³ UFC Sabouraud agar were isolated completely. From the isolated samples, 96 colonies were identified as representants of Deuteromycota and Ascomycota Filo. The most frequent ones were Penicilium (45%) and Aspergillus (33%). Penicilium was registered in all the substracta and the others had heterogeneous distribution. Among these colonies, Penicilium janthinellum and Aspergillus niger were predominating. As a result of the analyses carried on selective solid medium for secondary metabolites production, 29 moulds showed similar characteristics of mycotoxins and other compounds.. COnsidering the data, the profile of extracellular metabolites hsa been determined by veryfing that the all the species synthesized from one to three secondary metabolites in green and blue fluorescence, similar to the G1 and B1 aflotoxins. The thermal treatment reduced the contamination by moulds in flour samples. In conclusion, most of the cassava flour presented high mould contamination, among these there were species that expressed production of biocompounds with micotoxyns characteristics having as alternative the thermal treatment without modifying organoleptics characteristics. However they may be partially inactivated by thermic treatment.

Área de concentração: Ciência de Alimentos.