Determination of optimal grape and wine quality of Shiraz/Richter 99 and the relationship with seasonal variation in leaf and berry metabolism, as affected by microclimate

Project Number
WW 12-23

Project title
Determination of optimal grape and wine quality of Shiraz/Richter 99 and the relationship with seasonal variation in leaf and berry metabolism, as affected by microclimate

Project leader
Hunter, J J

Project description
Research was done on a Shiraz/R99 vineyard in the Stellenbosch region with the purpose of defining environmental, canopy and grape parameters that may be suitable as eventual practical indicators for obtaining particular grape and wine styles. During the course of the project, several facets of this aspect of cultivation were investigated, more often in collaboration with Spanish, French, Italian and Swiss researchers.

Optimal ripeness is defined according to the wine style that is required. The latter is ultimately dictated by the market. Soil and climate may have a dictating effect on typical expression of wine. The level of grape and wine quality achieved and the potential for obtaining different styles of wine are determined by the integrated effect of the natural characteristics of the terroir and technological intervention (long and short term cultivation practices). The growth conditions that the grapevine is subjected to should allow optimal metabolic activity in roots, permanent structure, canopy and grapes and the potential for these organs to develop and support each other until the desired grape quality and style is reached. Monitoring of morphological and physiological parameters in the canopy and grapes, ultimately displaying the integrated effect of the growth environment, is critical in our quest for finding indicators that may be associated with a particular grape and wine style.

This has not previously been investigated systematically. Vines were vertically trellised and spaced 2.75 x 1.5 m in north-south orientated rows on a Glenrosa soil and a west-facing slope. Micro sprinkler-irrigation was applied at pea berry size and at veraison stages. The 1.4 m canopies were shoot-positioned and topped. Fortnightly sampling was done from berry set up to two weeks post-veraison, after which harvesting for winemaking was done approximately every four days. Microclimate, vegetative, reproductive and physiological parameters were investigated and changes during alcoholic fermentation monitored at each harvesting stage. Wines were made and analysed. Similarities in patterns as well as various ratios between the different parameters were investigated. Results are argued against canopy performance, carbon allocation, water relations, production level, and sugar, acidity, anthocyanin, phenolic and tannin contents of the grapes as well as wine quality and composition. Ratios for potential practical use in determining optimal grape quality, time of harvesting and expected wine style are discussed. Ideally, the vineyard growth conditions should allow the prediction and distinction of different harvesting times, representing different styles of wine that can then either be made unilaterally or multilaterally by means of blending. Irrespective of the style of wine required, it is important that grapes are always harvested in a physicochemical state that would guarantee optimal quality of the product for which they are intended. Cultivation practices should be applied in such a way that the full grape quality potential of the vine is expressed on the particular terroir. If the terroir and cultivation practices do not allow normal physiological performance and grape potential to be fully expressed, as is often the case in practice, wine quality and style options will be reduced. Judicious selection of terroir and long-term practices is therefore critical.

The study clearly showed that optimal ripeness can not simply be described by the maximum accumulation of grape components, but rather represents a complex, particular combination of physiological or biochemical changes (in leaves and grapes in particular growth phases), physical changes (homogeneity of vine and canopy structure as well as bunch and berry size), and required grape and wine style and market preferences.

In this study, optimal harvesting time for a particular style of wine could be illustrated by using classic parameters of which information can be easily obtained during the growth season in the vineyard and in the winery by producers and wine makers. Positive indications of global applicability of the wine quality and style indicators found in this study (grape parameters and ratios) were evident.

Presentation(s)
Hunter, J J and Archer, E. 2002. Optimal ripeness. South African Society for Enology and Viticulture, Stellenbosch, South Africa, 18 January

Hunter, J J and Archer, E. 2002. Seasonal canopy management: Effect on microclimate, red and white grape quality and wine style. Seminar to VinPro Consultants, Robertson, South Africa,7 November

Hunter, J J and Archer, E. 2002. Grape and wine phenolics. Seminar to VinPro Consultants, Robertson, South Africa, 7 November

Deloire, A, Ojeda, H, Wang, Z, Hunter, J J, Paez, C, Martin, M and Carbonneau, A. 2003. Grapevine water status and berry ripeness – consequence for vineyard cultural practices. 27th National Congress of the South African Society for Enology and Viticulture, Somerset West, South Africa, 5-7 November

Pisciotta, A, Di Lorenzo, R and Hunter, J J. 2003. Shoot positioning: Effect on grape parameters. 27th National Congress of the South African Society for Enology and Viticulture, Somerset West, South Africa, 15-16 November

Pisciotta, A, Di Lorenzo, R and Hunter, J J. 2003. Shoot positioning: Effect on physiological parameters. 27th National Congress of the South African Society for Enology and Viticulture, Somerset West, South Africa. 15-16 November

Cloete, H, Archer, E and Hunter, J J. 2003. Shoot heterogeneity effects in a Shiraz/R99 vineyard. 27th National Congress of the South African Society for Enology and Viticulture, Somerset West, South Africa, 15-16 November

Hunter, J J, Volschenk, C G, Pisciotta, A, Archer, E, Nadal, M, Novello, V and Deloire, A. 2003. Determining optimal ripeness. 27th National Congress of the South African Society for Enology and Viticulture, Somerset West, South Africa, 15-16 November

Hunter, J J, Volschenk, C G, Pisciotta, A, Archer, E, Nadal, M, Novello, V and Deloire, A. 2004. Aspects concerning optimal grape ripeness and wine quality. Winetech VinPro Information Day, Stellenbosch, South Africa, 27 June

Hunter, J J, Volschenk, C G, Pisciotta, A, Archer, E, Nadal, M, Novello, V and Deloire, A. 2004. Aspects concerning optimal grape ripeness and wine quality. Seminar, May, Marsala, Sicily.

Cloete, H, Archer, E and Hunter, J J. 2004. Shoot heterogeneity effects in a Shiraz/R99 vineyard. Joint Conference on Viticultural Zoning, Cape Town, South Africa, 15-19 November

Hunter, J J, Pisciotta, A, Volschenk, C G, Archer, E, Novello, V, Deliore, A and Nadal, M. 2004. Role of harvesting time and optimal ripeness in zone and terroir expression. Joint Conference on Viticultural Zoning, Cape Town, South Africa, 15-19 November,

Nadal, M, Volschenk, C G and Hunter, J J. 2004. Phenolic extraction during fermentation as affected by ripeness level of Shiraz/R99 grapes. Joint Conference on Viticultural Zoning, Cape Town, South Africa, 15-19 November

Pisciotta, A, Di Lorenzo, R, Barbagallo, M G, Volschenk, C G and Hunter, J J. 2004. Phototropic and geotropic shoot orientation: Effect on physiological, vegetative and reproductive parameters. Joint Conference on Viticultural Zoning, Cape Town, South Africa, 15-19 November

Pisciotta, A, Di Lorenzo,R, Barbagallo, M G, Volschenk, C G and Hunter, J J. 2004. Shoot positioning: Effect on physiological, vegetative and reproductive parameters. Joint Conference on Viticultural Zoning, Cape Town, South Africa, 15-19 November

Deliore, A and Hunter, J J. 2004. Sugar loading and phenolic accumulation as affected by ripeness level of Shiraz/R99 grapes. Joint Conference on Viticultural Zoning, Cape Town, South Africa, 15-19 November

Hunter, J J. 2005. Optimal ripeness and zone – terroir expression. Seminar, University of Mendoza, May, Mendoza, Argentina.

Varvaro, G, Nadal, M, Lòpez, N and Hunter, J J. 2005. Influencia de la maduraciòn y calidad del vino tinto de Syrah. Gienol Symposium, Palencia, Spain, 3-4 June

Article
Costanza, P, Tisseyre, B, Hunter, J J, Deloire, A. 2004. Shoot development and non-destructive determination of grapevine (Vitis vinifera L.) leaf area, South African Journal of Enology and Viticulture, v. 25 (2) (p. 43-47)

Deloire, A, Hunter, J J. 2004. Berry composition as affected by bunch exposure, Progres Agricole et Viticole, (122) (p. 151-157)

Dissertation
Pisciotta, A. 2004. Modificazione dei rapporti ‘source-sink’ in Vitis vinifera L. mediante tecniche di gestione della chioma. University of Parlermo, Parlermo.

Thesis
Cloete, H. 2004. The effect of shoot heterogeneity on the physiology and grape composition of Shiraz/Richter 99 grapevines. MSc. University of Stellenbosch, Stellenbosch.

FinalReport.pdf

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