The use of resistant grape varieties and the non-conventional yeast Torulaspora delbrueckii as novel approaches for wine fermentation

This thesis delves into the intricate realm of winemaking, emphasizing the vital role of microorganisms, particularly non-Saccharomyces yeasts, in shaping the flavours and aromas of wine. Saccharomyces yeasts have conventionally dominated wine production, but recent advancements highlight the increasing significance of wild 'non-Saccharomyces' yeasts due to their pronounced influence on taste and aroma. Moreover, these yeasts can effectively modulate the fermentation process, resulting in wines with lower alcohol content. Investigating non-Saccharomyces yeast offers a promising avenue to enhance the sensory profile and overall quality of wines. In parallel, this study explores the transformative impact of utilizing resistant vine cultivars in viticulture and winemaking. These cultivars possess genetic traits that fortify them against prevalent grapevine diseases, reducing the reliance on synthetic pesticides and subsequently cutting down production costs. Resistant varieties also promote environmental sustainability by curbing chemical fertilizer usage, safeguarding the vineyard ecosystems' soil, water, and biodiversity. In this investigation The fermentation experiments involved the use of 14 different strains, including three strains of T. delbrueckii (G805.5, T910.5, and FRI 7.1) from various collection areas and three commercial T. delbrueckii strains (BIODIVA, SYMBIOSE, and QTAU) for comparison. S. cerevisiae EC1118 (Lallemand Inc., Montreal, Canada) was used in sequential fermentation and in single fermentation as a control strain. The best performances have been reported in FRI7.1 yeast, where ethanol decreased up to 19.68%. Our results showed that the decrease in ethanol is due to T. delbrueckii having a lower glycolytic capacity, diverting a significant portion of the sugars towards alternative metabolic pathways that produce organic acids, such as pyruvates and acetates, instead of ethanol. The PIWI analysis conducted in vines Cabernet Cortis and Sauvignon Nepis highlighted that the major characteristic changes like glycerol, ethanol, colour intensity, acetic acid, acetaldehyde and SO2 were due to their physiological properties, compared to Vitis vinifera varieties Cabernet Sauvignon and Sauvignon Blanc.