Fabiana Reinis Franca Passamani

Effect of temperature, water activity, and pH on growth and production of ochratoxin A by Aspergillus niger and Aspergillus carbonarius from Brazilian grapes.

The growth of ochratoxigenic fungus and the presence of ochratoxin A (OTA) in grapes and their derivatives can be caused by a wide range of physical, chemical, and biological factors. The determination of interactions between these factors and fungal species from different climatic regions is important in designing models for minimizing the risk of OTA in wine and grape juice. This study evaluated the influence of temperature, water activity (aw), and pH on the development and production of OTA in a semisynthetic grape culture medium by Aspergillus carbonarius and Aspergillus niger strains. To analyze the growth conditions and production of OTA, an experimental design was conducted using response surface methodology as a tool to assess the effects of these abiotic variables on fungal behavior. A. carbonarius showed the highest growth at temperatures from 20 to 33°C, aw between 0.95 and 0.98, and pH levels between 5 and 6.5. Similarly, for A. niger, temperatures between 24 and 37°C, aw greater than 0.95, and pH levels between 4 and 6.5 were optimal. The greatest toxin concentrations for A. carbonarius and A. niger (10 μg/g and 7.0 μg/g, respectively) were found at 15°C, aw 0.99, and pH 5.35. The lowest pH was found to contribute to greater OTA production. These results show that the evaluated fungi are able to grow and produce OTA in a wide range of temperature, aw, and pH. However, the optimal conditions for toxin production are generally different from those optimal for fungal growth. The knowledge of optimal conditions for fungal growth and production of OTA, and of the stages of cultivation in which these conditions are optimal, allows a more precise assessment of the potential risk to health from consumption of products derived from grapes.

Influence of physical and chemical characteristics of wine grapes on the incidence of Penicillium and Aspergillus fungi in grapes and ochratoxin A in wines

The incidence of filamentous fungi and toxin levels in grapes and wines varies depending on the variety of grapes, the wine region, agricultural practices, weather conditions, the harvest and the winemaking process. In this sense, the objective of this study was to evaluate the diversity of Aspergillus and Penicillium fungi isolated from wine grapes of the semi-arid tropical region of Brazil, evaluate the presence of ochratoxin A (OTA) in the experimental wine and verify if there is a correlation between occurrence of these fungi and the physicochemical characteristics of the wine grapes grown in the region. For the isolation of fungi we used the direct plating technique. The presence of OTA in the experimental wine was detected by high-performance liquid chromatography. The species found were Aspergillus niger, A. carbonarius, A. aculeatus, A. niger Aggregate, A. flavus, A. sojae, Penicillium sclerotiorum, P. citrinum, P. glabrum, P. decumbens, P. solitum and P. implicatum. All isolates of A. carbonarius were OTA producers and all P. citrinum were citrinin producers. The highest concentration of OTA was found in red wine (0.29μg/L). All species identified in this study, except A. flavus, showed a positive correlation with at least one physicochemical parameter assessed, highlighting the pectin content, total sugar, total acidity and phenolic compounds.

Effect of Fungicides on Growth and Ochratoxin A Production by Aspergillus carbonarius from Brazilian Wine Grapes

Prevention in the field of mycotoxin-producing fungi is the most effective strategy for controlling the presence of mycotoxins in foods. Chemical fungicides are widely used to protect crops, so their implications on mycotoxin production need to be considered. Therefore, the aim of this study was to evaluate the effect in vitro and on grapes of five fungicides commonly used on grape cultures in Brazil on Aspergillus carbonarius growth and ochratoxin A (OTA) production. At the doses recommended by manufacturers, most fungicides significantly reduced A. carbonarius growth and OTA production in vitro, whereas this effect was influenced by the type of fungicide, dose, and temperature. Temperature was the main factor that influenced the effectiveness of fungicides. In general, at 15°C, fungicides showed the greatest reduction on fungal growth and OTA production. Fungicide effect on grapes was different to that on a semisynthetic grape medium. All fungicide doses were not effective at controlling A. carbonarius in grapes. Thus, the direct effect of fungicides on grapes must be studied to obtain a better approximation of field conditions. The results indicate that the use of fungicides at the doses recommended by manufacturers is better than the application at low doses. This study showed that at the lowest doses, where fungal growth is not inhibited, fungicides positively stimulate OTA production.

Produção de Ocratoxina A por Aspergillus Carbonarius em Meio À Base de Cacau

Luisa Freire, Fabiana Reinis Franca Passamani, Danieli Cristina Schabo, Camila Alvarenga Freire, Luis Roberto Batista. Producao de Ocratoxina A por Aspergillus Carbonarius em Meio A Base de Cacau. In: Anais do 12o Congresso Latinoamericano de Microbiologia e Higiene de Alimentos MICROAL 2014 [= Blucher Food Science Proceedings, num.1, vol.1]. Sao Paulo: Editora Blucher, 2014. DOI 10.5151/foodsci-microal-086 Producao de Ocratoxina A por Aspergillus Carbonarius em Meio A Base de Cacau