## 1 Introduction
Sulphur dioxide-producing yeasts have also been investigated by [PERSON] and [PERSON] [14], and their effect on lactic acid bacteria was also tested. They found that the yeasts produced mainly acetaldehyde-bound sulphurous acid. The strains with the highest degree of inhibition were those that produced more sulphur dioxide; thus, it was not other toxic compounds that caused the failure of malotactic fermentation. If we are planning biological acid reduction in our wine, the sulphur dioxide-producing properties of the starter cultures must be taken into account. Biological sulphite produced by yeasts may have a chemical-biochemical stabilizing effect; however, it does not provide protection from a microbiological point of view. Thus, adequate sulphur dioxide dosing is still necessary [15]. The use of sulphur dioxide (SO\({}_{2}\)) is virtually indispensable in wine-making technology. Sulphur dioxide has antiseptic, reducing (antioxidant), flavor and aroma-preserving and color-stabilizing properties that are beneficial from a wine-making point of view. Although some of these functions can be replaced by alternative means, such as ascorbic acid addition or sterile filtration, the taste- and flavor-preserving effect of sulphurous acid, i.e., the binding of free acetaldehyde formed by oxidation, cannot be replaced by any other substance or means known today. In this way, it helps to prevent undesirable spoilage of the wine. In addition to the undoubted benefits of sulphurous acid, its allergenicity must not be overlooked. In sensitive consumers, it can cause headaches, the aggravation of asthma symptoms and coughing. For this reason, one of the recent developments in wine (and food) technology in general has been to reduce or minimize the use of sulphurous acid. One such option is the use of so-called sulphite-producing yeast cultures. Yeasts are capable of producing sulphur dioxide during alcoholic fermentation. In our experiments, polyphenols were investigated that are largely derived from grapes. They are one of the most important groups of compounds from an enoological point of view. They affect the stability of wine as they are oxidation-prone, highly antioxidant compounds; when oxidized, they can cause browning and other various precipitates. Theirpresence also affects the character of the wine. They are also responsible for the color of wines and shape the taste sensation of wines, such as astringent aromas (tannins). They are most important in red wines and have a small health effect. Sulphur dioxide prevents the rapid oxidation of these components [16]. In view of the above, the following objectives were formulated in our experiments: to investigate whether the sulphur content in wines after alcoholic fermentation still requires sulphurization and whether and to what extent the wines still need to be sulphurized in the longer term; the quantitative evolution of the components closely related to sulphurization--total polyphenols, leucoanthocyanins and catechins--was investigated; we also determined the amount of acetaldehyde, a compound that has a major influence on the organoleptic properties of wines. We also investigated whether the amount of sulphur dioxide formed after alcoholic fermentation is sufficient to ensure the quality of the wine.