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Vliv řízené mikrooxidace na technologii bílých vín =: The effect of controlled micro-oxygenation on technology of white wines /
Průšová, Božena
The PhD.-dissertation thesis deals with the effect of microoxidation on white wine technology. The varieties ‚Pinot Blanc‘ and ‚Pinot Gris‘ were used for the experiment in 2016 and 2017. Micro-oxygenation was applied in the first third of the fermentation process and during the maturation of wine. The effect of microoxidation on the course of fermentation was monitored. In micro-oxygenated wines, a statistically significant increase in the number of living yeast was observed immediately after the micro-oxygenation treatment, compared to the control experiment. The increase in cell mass was also observed by measuring the consumption of ammoniacal nitrogen and nitrogen contained in the amino acids. The results of the experiment show a higher consumption of ammonia nitrogen in the micro-oxygenated wine. The amino acid content did not change significantly. During the whole fermentation process, the course of antioxidant activity was monitored. There were no statistically significant differences between micro-oxygenated wines and control, in some cases the antioxidant activity of micro-oxygenated wines was significantly higher. This phenomenon can be explained by the formation of new phenolic compounds, such as gallic acid, which in some cases has been confirmed by HPLC results and theoretically higher production of yeast cell wall breakdown intermediates, which are potent antioxidants. An aromatic profile was determined in the resulting wine by GC analysis and sensory evaluation. Results from GC analysis show higher concentrations of higher alcohols and esters. The results of this experiment from the year 2016 have been successfully published in the reviewed periodical Ciencia e Técnica Vitivinícola: Bozena Prusova, Mojmir Baron, Effect of controlled micro-oxygenation on white wine, Ciencia Téc. Vitiv. 33 (1) 78-89 (2018), DOI: 10.1051/ctv/20183301078.
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Role kyslíku při výrobě bílých vín
Sapanelová, Claudia
Oxygen is an important factor active during all winemaking process. It is one of the main agents responsible for the oxidation of must and wine. The exposure to oxygen may have different effects, positive or negative, while it plays an important role in the formation of the organoleptic qualities of wine. In white winemaking, oxygen is known particularly for its negative impacts, especially for the colour browning and the losses of the fruity aroma, often one of the key qualities. White musts and wines are naturally prone to oxidation. This is due to the composition of their phenolic compounds, which are represented primarily by hydroxycynamic acids and their derivates. For this reason the white winemaking process is realised mostly in reductive conditions. Big emphasis is put on the protection against undesirable oxidation, particularly at the begining of the process. Deliberate introduction of oxygen is possible, it may be desirable especially during the alcoholic fermentation, but it has to be always well controlled. In this case, the contemporary winemaking aims to use the techniques of controlled aeration, hyperoxidation and micro-oxygenation respectively. The thesis contains a review approaching the issue, the impact and the management of oxygen in all stages of the white winemaking and present the techniques of controlled aeration and their possible utilization. The experimental part of the thesis is dedicated to the microoxygenation of white wines. Through the analytical comparison, aromatic profile and sensory analysis, of the micro-oxidized wine and the wine prepared in reductive conditions confirms the hypothesis regarding the positive effects of this technique in relation to the organoleptic qualities of wine.
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