Browsing by Author "Calado, Thalita"
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- Biodiversity of toxigenic fungi in the food chain and the co-occurrence of mycotoxinsPublication . Venâncio, Armando; Vale, Teresa Dias; Guimarães, Ana; Calado, Thalita; Rodrigues, PaulaFilamentous fungi are ubiquitous in Nature and may be found in any food crop, either in the field or during storage. With the exponential growth of the population, there is a worldwide challenge to reduce food losses. Food contamination by fungicauses great economic costs and seve ral health threats due to the toxicity and pathogenicity of some species. The biodiversity of this community, and the dynamics of the water activity, temperature and availability of carbon sources e volution, durillg the growing season, as well as in storage, determines the competitiveness of each species against ot her co-occurring fungai species. Some of these fungi are capable of producing a wide range of secondary metabolites - mycotoxins, which may accumulate in food chain, be resilient during food processing, and persist in the final food product. Contamination of food products with fungi is frequent , affecting food security and food safety. lhe ability of the different fungai species to compete under available conditions will influence the cocktail of mycotoxin that may occur. lhe study of the funqal biodiversity have been mainly carried out by surveyinq culturable strains (culture-dependent approaches), but recently metage nomics approaches have been used, enabling the possibility of spotting mycotoxigenic fungai strains, that are not easy to detect and isolate by conventional means. In this presentation, the biodiversity of fungai species in the food chain will be discussed, under a perspective of the co-occurrence of mycotoxins.
- Description of a strain from an atypical population of Aspergillus parasiticus that produces aflatoxins B only, and the impact of temperature on fungal growth and mycotoxin productionPublication . Arita, Camila; Calado, Thalita; Venâncio, Armando; Lima, Nelson; Rodrigues, PaulaIn this study, an atypical strain of Aspergillus parasiticus is described. This strain, reported from Portuguese almonds, was named Aspergillus parasiticus B strain. The strain is herein characterised at the morphological and physiological levels, and compared with the typical A. parasiticus strain and other similar species in section Flavi. Previously published morphological and molecular data support that the B strain is very closely related to the A. parasiticus type strain. However, while A. parasiticus typically produces aflatoxins B and G, B strain produces aflatoxins B only. Furthermore, this atypical strain showed to differ from the typical strain in the fact that higher growth (colony diameter) and aflatoxin B1 production were observed at 25 ºC than at 30 ºC, whereas the opposite was observed for the typical strain. This strain can become a major food safety concern in colder regions where the typical A. parasiticus strains are not well adapted.
- Efeito da radiação gama em soluções de aflatoxinasPublication . Calado, Thalita; Antonio, Amilcar L.; Cabo Verde, Sandra; Rodrigues, Paula; Botelho, M. Luísa; Abrunhosa, Luís; Venâncio, ArmandoOs fungos filamentosos, seres ubíquos na natureza, são muitas vezes parasitas de produtos alimentares, nomeadamente produtos agrícolas. A sua presença, embora encarada como natural, poderá não ser inócua, uma vez que alguns fungos são capazes de produzir compostos tóxicos, nomeadamente micotoxinas (e.g., aflatoxinas). As aflatoxinas, metabolito secundário produzido por Aspergillus flavus e Aspergillus parasiticus, são altamente tóxicas, mutagénicas e carcinogénicas. Por forma a garantir a segurança alimentar no que se refere à presença destes metabolitos em alimentos várias alternativas têm vindo a ser testadas. A irradiação de alimentos (e.g, radiação gama) é uma dessas alternativas [1]; no entanto, a identificação dos produtos de degradação das micotoxinas pela utilização desta tecnologia, assim como a avaliação da sua toxicidade, está por realizar. Com o trabalho realizado pretendeu-se verificar qual o efeito da radiação gama em soluções de aflatoxinas (B1, B2, G1 e G2). Para tal, soluções de aflatoxinas (B1, B2, G1 e G2) foram submetidas à radiação gama nas seguintes doses: 0, 0,5; 1,0; 3,0; 6,0 kGy. Após irradiação, a quantificação de aflatoxinas e a deteção de produtos de degradação foi efetuada por cromatografia líquida, com deteção por fluorescência e derivatização pós-coluna. Os resultados obtidos mostraram que existe uma diminuição da concentração de aflatoxinas nas soluções irradiadas, embora a sensibilidade de cada toxina à irradiação seja diferente. Para a dose mais elevada de radiação testada (6,0 kGy) a diminuição foi superior a 80 % para G1, G2 e B1. Além disto, em todas as amostras irradiadas, verifica-se a formação de compostos de degradação de aflatoxinas. A concentração destes compostos aumenta até à dose de 1,0 kGy, diminuindo nas restantes doses. O estudo da estrutura e da toxicidade destes compostos tem que ser levados a cabo de modo a ponderar a eficácia desta metodologia no controlo de micotoxinas em alimentos.
- Effect of gamma radiation on mycotoxins solutionsPublication . Calado, Thalita; Antonio, Amilcar L.; Rodrigues, Paula; Cabo Verde, Sandra; Venâncio, ArmandoDue to the high toxicity of mycotoxins, many methods have been used to reduce or eliminate them from food and feed. Gamma radiation is one technique that has been investigated with some promising results in degradation of some mycotoxins from food. The aim of this study was to clarify the effect of gamma irradiation on aflatoxin B1 (AFB1) aflatoxin B2 (AFB2), aflatoxin G1 (AFG1) and aflatoxin G2 (AFG2), ochatoxin A (OTA) and zearelone (ZEA). The effect of the presence of moisture during the irradiation process was evaluated. Solutions with the same initial mycotoxin concentration were submitted to gamma radiation doses ranging from 0 to 10.0 kGy, at distinct moisture level – dehydrated, in water, and in methanol:water solution. Mycotoxins levels were determined by high-performance liquid chromatography with fluorescence detection (HPLC-FL), and photochemical post-column derivatization (for aflatoxins). The results showed degradation of mycotoxins with doses above 3.0 kGy, but only when irradiated in aqueous environment. With dehydrated samples, no significant reduction was observed. The results showed that gamma radiation was effective in reducing the mycotoxins concentration, but the presence of water (mainly due to the formation of hydroxyl radicals) had a very significant effect. Acknowledgement: authors acknowledge the financial support of project ChestNutsRad, Programa Operacional do Norte (AdI, Portugal), contract number 13198. Thalita Calado and Luís Abrunhosa received support through grant SFRH/BD/79364/2011 and SFRH/BPD/43922/2008, respectively, from the Fundação para a Ciência e Tecnologia - FCT, Portugal.
- Effect of γ-radiation in the survival of Aspergillus parasiticus in chestnutsPublication . Calado, Thalita; Antonio, Amilcar L.; Rodrigues, Paula; Venâncio, ArmandoIn this study, the use of rays as an inactivation agent agains one of the most ubiquous and mycotoxigenic fungus - Aspergillus parasiticus - was studied. Chestnuts were previous incoulated with a spore suspension of one strain of A. parasiticus. After irradiation the growth of colonies were observed during 4 days. In general, the higher level of radiation the lower survival rate.