by Wessel du Toit, Petri de Beer & Albert Strever – Wineland
The main aim of this study was to investigate the colour and phenolic evolution of Shiraz wines obtained with different training and canopy treatments.
Phenolic compounds play an important role in the sensorial composition of red wines, such as Shiraz. However, how differences in the phenolic composition of Shiraz wines differ over time during ageing has not been well documented.
An experimental Shiraz block (clone 9 on 101-14-Mgt rootstock) at Stellenbosch University’s Welgevallen farm was used for this research. Vines were spaced 2.7 x 1.5 m and grown on a seven-wire training system for the vertical shoot positioning system (VSP) treatment. Part of this vineyard was converted to a Smart-Dyson (SD) training system. Upper and lower shoots of the SD were also harvested separately. An additional treatment consisted of a reduced treatment (R), by removing the top shoot and it’s grapes on a two bud spur at flowering time.
Grapes were harvested at the following parameters during the 2012 and 2013 vintages: pH 3.5 to 3.8, TA 4 to 4.5 g/ℓ and Balling 23 to 25 °Balling. Wines were made on small scale at the experimental cellar of the Department of Viticulture and Oenology (DVO) at Stellenbosch University, using Saccharomyces cerevisiae D21 (Lallemand) and Oenococcus oeni (Alpha, Lallemand) as lactic acid bacteria. After fermentation the wines were bottled in 750 mℓ bottles and aged. Analyses were done on the wines after the completion of malolactic fermentation, after six months (both 2012 and 2013) and 12 months (2012) of bottle ageing.