Thermal Pest Control in 'Tannat' grapes: Effect on anthocyanins, sensory and color of one-year-old wines.

Thermal pest control (TPC) is a technology that applies heated air in the vineyard to reduce pests. However, it can also alter grape anthocyanin synthesis in answer to temperature stress. The aim of this work was to determine the impact of TPC in 'Tannat' grape vineyards on wine quality. The major makers of quality considered in this study were the wine anthocyanin characterization by HPLC-PDA-MSn, beverage's sensory evaluation by descriptive analysis, and color parameters by instrumental analysis. A total of three experiments were performed in different harvesting years. In 2011/12 (Experiment I), four applications were performed from the flowering to fruiting. For the second experiment (2012/13), five applications were used only during fruiting. TPC treatment performed in 2013/14 (Experiment III) had a total of 19 applications from the flowering to harvesting. In the first experiment, TPC had increased wine pigments, color, and sensorial descriptors for visual (translucence) and gustatory (woody and body) perceptions. However, in the second experiment none of the evaluated wine quality parameters was affected by TPC (p≤0.05). In the last and longest experiment (19 applications), TPC has significantly increased some wine pigments content. Nonetheless, wine sensorial parameters were not affected. Since the climate was different among the years, it seems that TPC effect does not depend on the applications number and vegetable cycle period only, but also it can be affected by the weather conditions in which the vine is being cultivated. However, when TPC treatment has resulted in the greatest anthocyanin increment (Experiment I) some wine sensory descriptors were also improved.

Phenolic composition of grape and winemaking by-products of Brazilian hybrid cultivars BRS Violeta and BRS Lorena.

The phenolic composition of grapes and winemaking by-products (skins from grape marc, and lees) from Brazilian hybrid cultivars BRS Violeta (red) and BRS Lorena (white) was studied. Two vintages, five classes of phenolic compounds, and recovery yields using three dehydration techniques were considered: oven-drying at 50°C (D50); spray-drying (SD); and freeze-drying (FD). Recovery yields were higher using FD, although less expensive SD was a good alternative for Violeta lees. D50 caused great recovery reduction in Violeta but yielded similar results for Lorena. Violeta winemaking by-products were excellent sources of anthocyanins (mainly non-acylated and p-coumaroylated diglucosides), flavonols (mainly myricetin-based) and hydroxycinnamic derivatives (mainly caffeic-based). Lorena winemaking by-products contained lesser amounts of phenolic compounds, around a tenth of the values found in Violeta grapes for flavonols (mainly quercetin-based), hydroxycinnamic derivatives (mainly caffeic-based) and condensed tannins. Lorena cultivar contained small amounts of trans-resveratrol and its 3-glucoside, which were missing in Violeta cultivar.