Isolating exceptional yeast strains from the spontaneous microflora of Georgian endemic grape varieties Alexandrouli and Mujuretuli to enhance premium winemaking.

All the chemical transformations occurring during the process of alcoholic fermentation of grape must, which ultimately transforms it into a qualitatively distinct substance known as wine, are facilitated through the active involvement of the yeast enzyme system. Beyond the primary outcomes of fermentation, namely ethanol and carbon dioxide, wine yeasts also generate secondary products and by-products that intricately contribute to the wine's taste, aroma, and other sensory attributes. These characteristics are intertwined with the inherent qualities of the grape variety itself. Consequently, to achieve a truly superior and distinctive wine from this particular grape variety, it becomes imperative to utilize a yeast strain possessing precise and remarkable production, physiological, and biochemical traits within a pure culture. The objective of this study was to isolate novel industrial-grade pure wine yeast cultures from the spontaneous microflora present in the endemic grape varieties of Alexandrouli and Mujuretuli. Throughout the experimental process, a systematic selection approach was employed. This involved evaluating strains based on criteria such as cell proliferation rate, fermentation vigor, resistance to sulfites and alcohol, as well as the range of fermentation temperatures. As a result, two promising pure cultures, well-suited for the production of high-quality wine, were identified within the controlled laboratory conditions. Specifically, race AL-9 demonstrated potential for enhancing Alexandrouli wine, while race MU-23 exhibited promise for refining Mujuretuli wine. Furthermore, an examination of the relationship between these strains revealed that they do not exhibit antagonistic behavior. This discovery holds notable significance in the context of the fermentation process, particularly when considering their collaborative application in the production of a distinct locally-originated red wine known as „Khvanchkara“. Utilizing the aforementioned strains, an experimental batch of wine was produced using grape juice (with a sugar content of 20%) treated with Kadifit (400 mg/l). This process was carried out within controlled laboratory settings, during which a thorough assessment of various chemical parameters was conducted. These parameters included alcohol content, residual sugar levels, titratable acidity, and volatile acid concentrations. Ref. 9.