The thesis focuse on the effect of dose levels of sulfur dioxide in the must on the formation of carbonyl compounds. Futhermore it is concerned with oenological properties of sulfur dioxide, its forms and effects on wine. The thesis corroborates in detail carbonyl compounds bind sulfur dioxide and discusses their origin and various options to affect their quantity. Substances that may partially replace sulfur dioxide and thereby reduce its total quantity in wine are also debated. Experimental part of the thesis involved samples of wine differing in quantity of sulfur dioxide added to the must before fermentation and in forms of nutrition. Using the HPLC analysis concentrations of acetaldehyde, pyruvic acid, and 2-oxoglutaric acid were determined. The experiment demonstrated the effect of initial doses of sulfur dioxide on the amount of generated acetaldehyde and pyruvic acid. The effect of addition of thiamine, which reduces formation of pyruvic acid, was also shown.

The diploma thesis was focused on the possibility to control Varroa destructor in honeybees by using natural varroacides. In the literary section were processed findings about drugs and in the practical part there were described and evaluated the results. During the experiment the effectiveness of formic acid and fluvalinate and effectiveness of oxalic acid and amitraz were compared. Statistical evaluation of results has found that formic acid reached 78,6% efficiency, and oxalic acid on average, 93,8% efficiency, and this efficiency was equal or statistically insignificantly slightly higher compared to synthetic alternatives. Any negative effects of organic acids on the status and development of colonies were observed. Experiment results are particularly important for the treatment of resistant populations of mites and prevent cumulative acaricides residues in bee products.

The diploma thesis “Evaluation of acid changes in grapes and wines” is divided into theoretical and practical part. In the theoretical part were described individual acids, possibilities of their regulation in musts and wines and selected methods of their determination. In the practical part of diploma thesis, the parameters of the grapes (pH, total titratable acids, tartaric acid and malic acid) were observed during the ripening period. The varieties Müller Thurgau, Pálava, Frankovka and Svätovavrinecké were studied. Berries were taken at regular weekly intervals from 2.8. to 20.9. 2018. In the second part of the experimental part of the work, the wines were monitored in three stages of vinification. The pH, total titratable acid, tartaric, malic and lactic acid parameters were monitored. The results were interpreted using tables and graphs. Subsequently, they were statistically evaluated and described.

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Data shows that if the year is similar to year 2013, as regards to the increased content of titratable acid, there can be a longer maceration pulp, which may serve as the future harmoniousness wine. Appropriate sufficient time of maceration for any decrease in titratable acidity corresponds to the period of maceration form 4 to 12 hours. Regarding the tartaric acid and malic acid, the time of maceration appears to be approximately 8 hours. From this time forth there may be rises in values of malic acid,which can cause microbiological instability. If we wanted to get the largest share of the health-promoting substances of this year, the must had to be macerated at least 48 hours.

Efforts to reduce sulphur dioxide in wine have been the subject of wine interest for several years. Research over recent years has shown the effectiveness of saturated higher fatty acids as an alcohol fermentation inhibitor, even in the production of wine with higher residual sugar. The principle of the function of C8, C10 and C12 fatty acids is simple. They enter the body yeast, which subsequently change their structure and the cell will become permeable to other substances, and thus is not working - yeast stops working and alcoholic fermentation is stopped. The mixture of higher fatty acids of C8, C10 and C12 in the ratio 2 : 7 : 1 can during application of 10 mg.l-1 reduce the necessary dose of SO2 to several tens mg.l -1. The results show that administration of 10 mg.l-1 of a mixture of higher fatty acids in combination with 30-40 mg.l-1 SO2 is as effective as a dose of 60 mg.l-1 SO2 itself. In addition to the demonstrable effect of stopping alcohol fermentation, the HFA (resp. MCFA) mixture appears to be promising before referral (especially for wines with higher residual sugar).

The theme of this work is a method of refermentation wine at 4% alcohol by volume, focusing on the elimination of acetic acid or during fermentation. This is the old method, which is used to correct the volatile wines. The introduction describes the alcoholic fermentation. Further disclosed are methods of inoculation, pathways of acetic acid, both in the vineyard and in the winery. Part of the work is devoted to the ability of yeast to eliminate acetic acid. She is also sensory evaluation of wines. The practical part is devoted to refermentation of volatile wine with musts in the varieties Pinot Blanc and Lemberger, the disappearance of acetic acid during fermentation.