Initiated by the Association “Wine Route of Etyek Wine District”, the objectives of this study were to isolate and identify autochthonous yeast strains from local wines and to determine their oenologically important properties. The first aim of this work was to characterize the taxonomic and phenotypic diversity of the representative Saccharomyces yeast strains that dominate the spontaneous fermentations in this wine district. The results obtained by molecular ribotyping (ARDRA) revealed a strong dominance of S. cerevisiae, but S. bayanus var. uvarum was also present sporadically. Some of the natural isolates exhibited high volatile acid production or poor fermentation capacity, which imply a quality risk in spontaneous fermentations. Most of the isolates, however, displayed good oenological features during lab scale fermentations. As the second aim of this work, the most promising, selected strains were further tested for oenological properties in microvinification scale and, finally, in large scale fermentations. The analytical and sensory analysis proved that selected strains, including S. bayanus var. uvarum, can be used as local starter cultures, which may contribute to the typicality of the local wines in comparison with commercial starters.
Authors:O. Csernus, J. Beczner, F. Sebők, M. Tóth, and Cs. Dobolyi
The surface microbial contamination is of great interest in case of fruit because of the threat of postharvest spoilage. Apple is a valuable product from growing, commercial, as well as from nutritional points of view. Apple diseases during the growing season can be satisfactorily controlled by different plant protection technologies, but postharvest decay of apples caused by the so called storage moulds cannot be completely avoided. Cold storage — alone, or in combination with other methods — is the main technology used to successfully prolong the shelf life of apples. The origin of the moulds causing the decay of apples during storage is not well understood. In this work the surface mycobiota of apple fruit grown in Soroksár, in the orchard of the Corvinus University of Budapest was investigated.
Authors:O. Csernus, I. Bata-Vidács, J. Farkas, and J. Beczner
The effect of water activity (0.85–0.99 aw) and temperature (20–35 °C) on growth of two potentially toxigenic moulds, Aspergillus niger and Penicillium expansum, were studied. On the basis of the measured colony diameter ComBase DMFit program was used to estimate the lag phase and growth rate. Similar results may provide basis for the risk assessment of fungal growth (and also for the possible mycotoxin contamination) in food and feed plants in the vegetation season due to the climate change (global warming), and also during unfavourable storage conditions.
Authors:Cs. Dobolyi, K. Inotai, I. Bata-Vidács, D. Sárkány, O. Csernus, S. Kocsubé, B. Tóth, A. Szekeres, and J. Kukolya
Aspergillus strains were isolated from Hungarian mills in order to get information on the appearance of sterigmatocystin (ST) producing moulds, whose presence has never been demonstrated in Hungary. Fungal isolates were classified into nine morphotypes, sections Nigri, Nidulantes, Versicolores (two morphotypes), Circumdati, Flavi (two morphotypes), Clavati and Terrei by classical mycological assays. ST producing strains could be classified into section Versicolores. ST production of the isolates was assessed by liquid and solid phase growth experiments and compared to ST producing reference strains: Aspergillus pepii SzMC 22332, Aspergillus versicolor SzMC 22333, Aspergillus griseoaurantiacus SzMC 22334 and Aspergillus nidulans RDIT9.32. Four of our isolates marked as Km11, Km14, Km26 and Km31 showed ST production in liquid medium. ST production on solid phase corn grit substrate was measured after three weeks of incubation, and Km26 isolate proved to be the most prominent with a toxin concentration of 277.1 μg g−1, surpassing all reference strains. The toxin-producing ability of Km26 isolate was also tested in a field experiment, where corn was infected. By the end of the experiment, ST level of 19.56 μg kg−1 was measured in infected corn.
Molecular taxonomic identification of the Km26 strain was performed using internal transcribed spacer (ITS), calmodulin and tubulin sequence analyses. Based on these studies, strain Km26 was identified as Aspergillus creber.
Here we report that an ST-producing A. creber strain has appeared in Hungary, and the Km26 strain is the first known extreme ST-producing mould in this country. As a result of climate change, aflatoxin B1 producing Aspergillus flavus strains have appeared in Hungary in the last decade. As strain Km26 is the only A. creber isolate in Hungary so far, there is no sign of mass prevalence, and due to the lower temperature optimum of the species compared to A. flavus, its appearance is probably not related to climate change.