Effects of successive harvesting in the same year on quality and bioactive compounds of grapes and juices in semi-arid tropical viticulture.

The technological and polyphenolic parameters of grapes for juice processing obtained from successive harvests were studied in semi-arid tropical viticulture. Red grapes "BRS Violeta" and "Isabel Precoce" were harvested during the same year and analyzed based on a multivariate approach that included climatic variations. The grapes were marked by variations in flavonoid compounds, particularly anthocyanins. Temperature, global radiation, air velocity and evapotranspiration rates were associated with higher accumulation of bioactive polyphenols in grape berries and juices. The temperatures in February were associated with higher antioxidant activity in grape peels, while the highest thermal amplitude in August and November favored the accumulation of anthocyanins up to 564 mg kg-1. Flavanols and procyanidin compounds were more abundant in seeds when the maximum thermal amplitude was 13.8 °C. The climatic data together with the polyphenolic results point out useful information about appropriate periods for harvesting grapes with high phenolic content in tropical areas.

Development and validation of automatic HS-SPME with a gas chromatography-ion trap/mass spectrometry method for analysis of volatiles in wines.

An automated headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-ion trap/mass spectrometry (GC-IT/MS) was developed in order to quantify a large number of volatile compounds in wines such as alcohols, ester, norisoprenoids and terpenes. The procedures were optimized for SPME fiber selection, pre-incubation temperature and time, extraction temperature and time, and salt addition. A central composite experimental design was used in the optimization of the extraction conditions. The volatile compounds showed optimal extraction using a DVB/CAR/PDMS fiber, incubation of 5 ml of wine with 2g NaCl at 45 °C during 5 min, and subsequent extraction of 30 min at the same temperature. The method allowed the identification of 64 volatile compounds. Afterwards, the method was validated successfully for the most significant compounds and was applied to study the volatile composition of different white wines.