Browsing by Author "Vipotnik, Ziva"
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- Aspergillus westerdijkiae as a major ochratoxin A risk in dry-cured ham based-mediaPublication . Vipotnik, Ziva; Rodríguez, Alicia; Rodrigues, PaulaPenicillium nordicum is well known for its ability to produce high amounts of ochratoxin A (OTA) in cured meat-derived products. On the other hand, Aspergillus westerdijkiae, one of the most relevant OTA-producing species of the genus Aspergillus, is usually considered a major risk in carbon-rich food matrices of plant origin. The objective of this work was to evaluate, for the first time, the ecophysiological conditions governing growth, OTA production and sporulation of A. westerdijkiae (the type-strain and one ham-native strain), in comparison with P. nordicum, in dry-cured ham based medium. For that purpose, the interaction between temperature (15, 20, 25 and 30°C) and water activity (aw) (0.99, 0.97, 0.93, 0.90 and 0.85), achieved with a combination of ionic (NaCl) and non-ionic (glycerol) solutes, was studied by using dry-cured ham-based medium as a model system. Different OTA production profiles were found between the two genera, and also between the two strains of A. westerdijkiae, mostly in terms of amounts of OTA produced. The optimal OTA production conditions for A. westerdijkiae were at 0.94-0.97 aw and 20-25°C, and for P. nordicum at 0.95-0.97 aw between 18 and 22°C. Under these conditions, A. westerdijkiae produced 1934ng/g agar, while P. nordicum produced 712ng/g. None of the strains was able to produce detectable amounts of OTA at 0.85 aw, under all temperatures tested. Growth and sporulation were not good indicators of OTA production by A. westerdijkiae or P. nordicum. The results obtained show that A. westerdijkiae may represent a great potential risk of OTA contamination in dry-cured ham due to the high production under a wide range of conditions. Knowledge of the ecophysiology of important Aspergillus and Penicillium species and of their adaptability to the matrices can be determinant to adopt appropriate technological modifications during ham ripening process.
- Produção de Ocratoxina A em presunto por Aspergillus westerdijkiaePublication . Vipotnik, Ziva; Rodríguez, Alicia; Rodrigues, PaulaAspergillus westerdijkiae é um dos mais importantes fungos produtores de Ocratoxina A (OTA). Apesar de ser maioritariamente associado a alimentos de origem vegetal, pode também ser encontrado em produtos cárneos curados, onde Penicillium nordicum é considerado o mais importante produtor de OTA. O objetivo deste estudo foi avaliar as condições ecofisiológicas que influenciam o crescimento de A. westerdijkiae e produção de OTA, em comparação com P. nordicum. Para esse efeito, foi testada a inteação entre os fatores temperatura (15, 20, 25 and 30 °C) e atividade de água (aw) (0.99, 0.97, 0.93, 0.90 and 0.85) obtida pela combinação de solutos iónicos (NaCl) e não-iónicos (glicerol), usando meio de cultura à base de presunto como modelo. Os dois fungos em estudo apresentaram perfis de produção de OTA significativamente diferentes. As condições ótimas de produção de OTA por A. westerdijkiae foram 0,94 – 0,97 aw e 20 – 25 °C, e por P. nordicum foram 0,95 – 0,97 aw e 18 – 22 °C, mas A. westerdijkiae produziu quantidades de OTA significativamente superiores. Nenhuma das espécies produziu a micotoxina a 0,85 aw. O crescimento de ambos os fungos não mostrou ser um bom indicador da produção de OTA. Os resultados obtidos mostram que A. westerdijkiae pode representar um elevado risco de contaminação com OTA em presunto devido à produção de elevadas quantidades da micotoxina numa gama alargada de condições ambientais habitualmente encontadas durante o processo de cura dos produtos cárneos.
- Production of ochratoxin A in dry-cured ham based-media by Aspergillus westerdijkiaePublication . Vipotnik, Ziva; Rodríguez, Alicia; Rodrigues, PaulaOchratoxin A (OTA) is a secondary metabolite produced by Penicillium and Aspergillus genera and is considered one of the most important mycotoxins occurring in animal and human food chains. Oxidative stress, inhibition of protein synthesis, disruption of calcium homeostasis, inhibition of mitochondrial respiration and DNA damage are some of OTA´s mechanisms of action causing teratogenicity, immunotoxicity, neurotoxicity and mostly nephrotoxicity. In dry-cured and fermented meat products, OTA is strongly associated with Penicillium nordicum (PN), but Aspergillus westerdijkiae (AW), a strong OTA producer usually associated with contamination of coffee beans, has also been found to be responsible for high OTA levels in cured meat products. Fungal growth and OTA production in meat products can be influenced by environmental conditions, physico-chemical characteristics of the matrix, and its endogenous flora. OTA is highly stable, so its destruction during normal food processing is very difficult to achieve.