Banca de DEFESA: ERIKA SAMANTHA SANTOS DE CARVALHO

AGRONOMIC AND OENOLOGICAL INTERVENTIONS TO IMPROVE THE QUALITY OF NATIONAL TOURIGA WINE PRODUCED IN SUBMEDIO FROM SÃO FRANCISCO VALLEY

Tropical viticulture, ripeness grape, maceration, metabolomic profile, sensory profile

The Sub-middle São Francisco Valley region in Northeast Brazil stands out for its unique approach to viticulture, known as tropical viticulture. Differing from conventional winegrowing regions, this area can produce up to two and a half harvests annually in the same area, spread throughout the year. In this scenario, fine wines made from the Vitis vinifera L. grape, including those made from the Touriga Nacional cultivar, have gained recognition on the international stage. This study aimed to propose agronomic and enological alternatives to improve the sensory quality of tropical red wine 'Touriga Nacional' produced in the Sub-middle São Francisco Valley. The impact on physicochemical, metabolomic, sensory, and antioxidant capacity of the harvest time, grape maturation stage, and maceration duration during traditional vinification (simultaneous maceration with alcoholic fermentation) were investigated. Experimental wines were produced from grapes harvested at three maturation stages during two different periods: harvest I ("summer harvest," starting from 02/09/2017) and harvest II ("winter harvest," starting from 07/12/2017). Grapes were harvested at three maturation stages (before, during, and after technological maturation), ranging from 21.6° to 24.5° Brix in harvest I and from 22.5° to 24.6° Brix in harvest II, with seven-day intervals between harvest dates. During vinification, maceration was carried out for three different periods (7, 14, and 21 days) for each harvest period and grape maturation stage. Additionally, grape musts for analysis were collected immediately after vinification and throughout the maceration stage for the treatment made with overripe grapes (around 24° Brix) and 21 days of maceration. This thesis was divided into four chapters, the first being the bibliographic reference. The second chapter focused on the article "Extended maceration of must improves phenolic composition and antioxidant potential of Touriga Nacional tropical wines," where results indicated that extended maceration increased phenolic compound concentration (mainly flavanols), color intensity, and wine antioxidant capacity. In the third chapter, the article "Effect of grape maturation stage and maceration time depending on grape harvest time of the year on the physicochemical, sensory, and nutraceutical profile of the tropical red wine from the Touriga Nacional cultivar" showed that the grape ripeness at harvest had a greater impact on the physicochemical composition and phenolic compound content of the wines, including color intensity, total polyphenol index, alcohol content, and the concentration of most phenolic compounds being higher in wines made from grapes harvested at a more advanced stage. However, extending maceration to more than 14 days increased the antioxidant capacity of 'Touriga Nacional' wine. Grape harvesting in the winter promoted higher content of phenolic compounds of the classes of phenolic acids, monomeric anthocyanins, stilbenes, and flavanols in tropical wine. In the fourth chapter, "1H NMR and UPLC-HRMS-based metabolomic approach for evaluation of grape maturity and maceration time of Touriga Nacional wines and their correlation with chemical stability," advanced chemical analyses were used to understand how harvest time, grape maturation, and maceration time affect metabolomic profile of Touriga Nacional wines. It was found that wines made from grapes harvested earlier and macerated for a shorter time had more phenolic acids, while those with riper grapes harvested in July and longer maceration had more flavanols. Additionally, wines made from ripeness grapes were more stable. Thus, the results of this study are crucial in expanding our understanding of the processes involved in red wine production, especially in regions with unique climatic conditions like the Sub-middle São Francisco Valley. This information can guide producers in  making crucial decisions related to harvesting and maceration aiming to achieve highquality wines and chemical stability. The relevance of this study is evident in providing valuable insights for producers in the Sub-middle São Francisco Valley and others tropical regions.