Efeito da tecnologia Thermal Pest Control sobre uvas e vinhos

Abstract

Thermal Pest Control (TPC) is an alternative thermal technology in vineyards, which was developed for protecting plants from frost and subsequent fungal diseases. Moreover, there are indications that this technology can trigger changes in defensive metabolism by stimulating the production of phenolic compounds. In view of this, the objective of this study was to evaluate the effect of TPC technology in grapes and its impact on the phenolic composition and quality of wines. The vineyards of the cultivars 'Tannat' received 4, 5 and 19 applications of thermic treatment in the 2011/12, 2012/13 and 2013/14 crops, respectively; the Cabernet Sauvignon received 19 applications in the 2013/14 crop. The grapes were analyzed for industrial and phenolic maturation, followed by vinification in laboratory scale. The wines produced were stored for 1 and 12 months for physicochemical, chromatographic and sensory analysis. Thermic treatment influenced the industrial ripening of the „Tannat‟ grapes but without changing the extractability. For the Cabernet Sauvignon grape TPC did not alter the industrial maturity, reducing the tannins of the shells and increasing the ones of the seed. The color intensity was increased in Cabernet Sauvignon wine remaining high up to 12 months. In the anthocyanin profile of wines produced from 'Tannat' grapes which received four applications in the 2011/12 crop, there was an increase of 49.8% in monomeric anthocyanin, 51.4% in pyranoanthocyanins, 7.0% direct condensation products and 39.6% condensation product mediated by acetaldehyde. In wines from grapes of the same variety in the 2012/13 crop, which received 5 applications of TPC there was no significant difference in anthocyanins and derivatives due to the high rainfall. In the 2013/14 crop, the wines produced with 'Tannat' grapes which received 19 TPC applications increased by 30.6% in monomeric anthocyanins and 11.5% in the direct condensation products, other compounds reduced. In the Cabernet Sauvignon wine made from grapes treated with TPC there was an increase of 4.5% in monomeric anthocyanin, 29.4% in pyranoanthocianins and 29.5% in the direct condensation products, without the formation of acetaldehyde derived compounds. In sensory, red color (p≤0.10) and woodsy flavor (p ≤ 0.05) were more intense in wine grapes treated with TPC. Nevertheless, the olfactory red fruits attribute was less intense with the thermic treatment. Visually, there was an increase in the intensity of tears (p≤0.05), however, not being related to alcohol. As to the acceptability, both wines were described as "moderately liked". Thus, the TPC treatment depends on the number of applications, the management on different weather conditions to promote proper physiological response in grapes and wine for their phytochemical and sensory quality.