Phenolic typicality and deterioration study of red wines from the Sub-middle São Francisco Valley

Abstract

This work evaluated the phenolic profile and chemical traits of red wines from Sub-middle São Francisco Valley (SSFV), Brazil, to propose the phenolic typicity and study deterioration mechanisms of this peculiar wine-producing frontier. Then, six varietal red wines were obtained from the grape cultivars (Vitis vinifera L.) Syrah, Tannat, Petit Verdot, Merlot, Malbec, and Tempranillo, harvested in 2019 second semester in SSFV. All the wines were elaborated following the traditional winemaking, without corrections, and applying 96 hours of maceration. Syrah is the better-adapted grape variety in SSFV, followed by Tempranillo; but the other ones are non-trade-grown or few commercially explored. Tannat is a grape variety that has a high content of phenolic compounds, showing intense coloration, well-bodied, and great aging potential, which becomes one great option to use in SSFV. Therefore, this work was divided into three chapters. The first one aimed to compile scientific knowledge on red wines from the SSFV, regarding sensory and chemical traits, and both the edaphoclimatic conditions and scientific perspectives currently approached in the SSFV. The second chapter aimed to characterize for the first time the phenolic typicity and antioxidant potential of Tannat wine from this region, comparing it with Syrah, the better-adapted variety in SSFV. Despite the short-applied maceration, the tropical Tannat had great phenolic contents and antioxidant activity, standing out the compounds trans-caftaric, malvidin-3-O-glucoside, and procyanidin B1. Tannat had the potential to be an important grape variety in tropical wine-producing regions in Brazil, presenting high bioactive contents and typical traits of these regions. The other varieties were used to study the deterioration mechanisms under primary conditions and manufacturing interventions. Then, the third chapter aimed to explain how the high pH and short maceration time influence the physical and chemical deterioration of red wines. Color, acetaldehyde, and free SO2 were used as indicators of spoilage, and physicochemical analyses, higher alcohols, total phenolics, monomeric anthocyanins, antioxidant activity, and individual phenolic characterization were studied to make sure about the influence pathways of pH and maceration over the deterioration. Tempranillo wine was the sample with the highest deterioration rate, pH and lowest color, monomeric anthocyanins, and catechins. Petit Verdot wine was the lowest deteriorated sample, also having the highest total phenolic compounds, color, anthocyanins, catechins, and antioxidant activity. pH had a strong correlation with anthocyanins polymerization and acetaldehyde. Caffeic and ρ-coumaric acids were related to major deterioration rates, whereas catechins, procyanidins, and anthocyanins were related to antioxidant activity and more resistance to oxidation. Only high pH values may not be enough to spoil the wine, as other parameters may provide chemical stability, such as phenolic compounds and their antioxidant activity. Then, red musts with high pH may require longer maceration time to improve the major shelf-life of these wines.