SPECIFIC FEATURES OF NITROGEN METABOLISM DURING FERMENTATION OF MUST FROM WHITE GRAPE VARIETIES GROWN IN THE ODESSA REGION

Abstract

For wine quality management, nitrogen metabolism should be considered as a key process in the system “grape – wine.” Nitrogen is one of the dominant elements a grapevine receives from the soil. It is important in many biological processes of the plant itself and of the microorganisms involved in fermentation. Nitrogen-containing compounds are nutrients necessary for yeast growth, in particular, for stable fermentation. This group of compounds directly and indirectly affects the aromatic and taste qualities of wine during its maturation and largely determines its stability. Nitrogen compounds are transferred to wine directly from grapes and yeast during fermentation. Since their role in the formation and maturation of wine is significant, it is highly important to regulate their metabolism in the fermenting must. On analysing literature references and summarising the information on the metabolism of nitric substances, a scheme has been developed reflecting how these substances influence the formation of the quality characteristics of grape wines. The paper presents the results of studying the metabolism of total nitrogen and amino nitrogen in grape must during its fermentation. The grape variety considered in the research was Sukholimansky White bred by the National Science Centre “Tairov Institute of Viticulture and Winemaking” and harvested in 2015–2017. It has been established that nitrogen metabolism during fermentation does not depend on the feedings added. However, the yeast race affects the physicochemical parameters, namely the content of volatile acids. It has been observed that during fermentation, the amine nitrogen concentration decreases by 90% and the total nitrogen concentration by 40–50%. Regarding the factors that effect on the quality characteristics of wines produced in the South of Ukraine, the physicochemical parameters of wine materials can be improved by using the active dry yeast Vitilevure Quartz and the nutritional supplements Actiferm 1 and Actiferm 2, in combination with aeration. This allows revealing fruity aromas, and achieving the right acidity and harmony of taste due to the presence of the descriptors (butter, apple, peach, apricot, and geranium) characteristic of the grape variety Sukholimansky White.