Flavonoids and C13-norisoprenoids in Vitis vinifera L. cv. Shiraz: relationships between grape and wine composition, wine colour and wine sensory properties

Background and Aims: This study investigated flavonoid composition and C-13-norisoprenoids (beta-damascenone and beta-ionone) in Shiraz grapes and wines, their relationships and links to wine sensory properties. Methods and Results: Differences in the grape berry flavonoid profile were created by exposing bunches to varying levels of sunlight intensity through canopy manipulation. Grapes were harvested at similar maturity and three replicate wines were made for each treatment in both vintages. Grapes produced under shaded canopy conditions had reduced anthocyanins and skin tannins, but little effect on seed tannins was observed. Pigmented polymers and tannins in wines were related to berry flavonoid composition (anthocyanins, skin and seed tannins, and their ratios). In grapes and wines, no significant effects were observed in response to canopy manipulation for two hydrolytically released C-13-norisoprenoids, beta-damascenone and beta-ionone. Relationships were established for wine flavonoid composition, wine colour density, sensory perception of the astringency-related mouth-feel attributes and a quality scale. A positive relationship between wine quality score and hydrolytically released beta-damascenone in both berries and wines was found, but not for free beta-damascenone or any quantified forms of beta-ionone. Conclusion: Higher concentrations of anthocyanins and skin tannins in berries, coupled with a lower concentration of seed tannins were associated with higher wine quality. The ratio anthocyanins*skin tannins/seed tannins is proposed as an indicator of wine flavonoid composition, wine colour and wine quality. Excessive canopy shade was detrimental to berry and wine composition and intensified sensory detection of 'straw' and 'herbaceous' characters in the wines. Significance of the Study: This study increases the understanding of the balance and composition of flavonoid compounds and C-13-norisoprenoids in berries and their relationship with wine composition and wine sensory properties, but also highlights the importance of a canopy microclimate assessment.