Comprehensive two-dimensional gas chromatography coupled with Tof-MS, a powerful tool for analysis of the volatomes of grapes and wines

The use of multivariate statistics to correlate chemical data to spectral information seems as a valid alternative for the quantification of red wine phenolics. The advantages of these techniques include simplicity and cost effectiveness together with the limited time of analysis required. Although many
publications on this subject are nowadays available in the literature most of them only reported feasibility
studies. In this study 400 samples from thirteen fermentations including five different cultivars plus 150
wine samples from a varying number of vintages were submitted to spectrophotometric and chromatographic phenolic analysis.

Adrenaline (epinephrine) belongs to catecholamine class. It is a neurotransmitter and both a hormone which is released by the sympathetic nervous system and adrenal medulla in response to a range of stresses in order to regulate blood pressure, cardiac stimulation, relaxation of smooth muscles and other physiological processes. Adrenaline exhibits an effective antioxidant capacity (1). However, adrenalin is capable to auto-oxidation and in this case it generates toxic reactive oxygen intermediates and adrenochrome. Under in vitro conditions, auto-oxidation of adrenaline occurs in an alkaline medium (2).

Fermentative aromas (especially esters and higher alcohols) highly impact the organoleptic profile of young and white wines. The production of these volatile compounds depends mainly on temperature and Yeast Available Nitrogen (YAN) content in the must. Available dynamic models predict the main reaction
(bioconversion of sugar into ethanol and CO2 production) but none of them considers the production kinetics of fermentative aroma compounds during the process of fermentation. We determined the production kinetics of the main esters and higher alcohols for different values of initial YAN content and temperature, using an innovative online monitoring Gas Chromatography device.

Anthocyanin accumulation and extractability were studied in Tannat, Cabernet Sauvignon and Merlot grapes produced in the south of Uruguay in two consecutive seasons. Typical cultivation situations employed in the region for each variety were considered. A follow-up was carried out, considering 60 plants per vineyard, and the harvest was determined according to the technological indices of maturity. Samples of grapes were taken in duplicate in each vineyard periodically along grape maturation. The basic composition, polyphenolic potential and anthocyanin extractability were determined. Also, half of grapes were frozen and later peeled; skin extractions over 24 hs with a solution of 12% ethanol and pH 3.2 were carried out. The anthocyanin contents of the extracts obtained were determined by HPLC-DAD. The levels of anthocyanins reached the highest values before technological maturity. Anthocyanin extractability had a decrease during grape maturation.

Chemical and sensory changes occurring in red wine during ageing in oak barrique are due to the slow and gradual entrance of oxygen along with a release of ellagic tannin from the wood. Though oxygen can enter the cask through the bunghole, it is not clear the role of permeation through the wood staves as well as the amount of oxygen entering by permeation. The distribution of the released ellagic tannins in the wine ageing is also unknown. The oxygen passing through the bunghole may have a different wine ageing effect compared to the oxygen permeating through the wooden staves owing to the uneven ellagic tannin concentration throughout the wine.