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US postgraduate courses keep abreast of latest technology

Postgraduate students and staff at the Department of Viticulture and Oenology. From left: Mareli Laker, Victoria Carey, Abraham de Villiers, Ronel Bester, Jean-Louis de Klerk, Marina Bruwer, Jacques Ferreira, Prof Melané Viviers, Dr Maret du Toit, Sunet van Zyl, Elmarie Swart, Dr Pierre van Rensburg, Carli Kieck, Riaan Wassüng, Henning Burger, Léan Viljoen, Anita Oberholster and Hanlé Cloete.

Both the viticulture and oenology curriculums at the Department of Viticulture and Oenology, offered by the Faculty of Agriculture and Forestry at the University of Stellenbosch, were adapted this year at the postgraduate level to ensure that the courses remain industry oriented and keep students up to speed with cutting edge technology.
The viticulture course now includes a module on the use of GIS (Geographic Information System) and distance observation in agriculture, as well as the relevance of modelling for the analysis of spatial patterns in agriculture, with specific reference to viticulture. The extremely important issue of environmental management is included in the course followed by oenology students.
The lecturing team at the Department has been reinforced by an additional post which is funded by the Deciduous Fruit Producers' Trust. Henning Burger has been appointed in this post to reinforce the table grape team. The other lecturers are Profs Piet Goussard, Eben Archer, Melané Vivier, and Drs Pierre van Rensburg and Maret du Toit, as well as Charl Theron, Wessel du Toit and Victoria Carey. Extraordinary professors are Sakkie Pretorius, Marius Lambrechts and Kobus Hunter.
This year the department has altogether 22 postgraduate students, three of whom are enrolled for PhDAgric, 13 for MScAgric and six for HonsBScAgric.
The six honours students are newly registered postgraduate students, while Mareli Laker is engaged in a new project for her master's degree. The supervisors and research projects are as follows:
Jean-Louis de Klerk
HonsBScAgric (Oenology)
The influence of certain vinification practices on the phenolic and colour composition of wines made from Roobernet grapes.
Supervisors: Mr Charl Theron and Ms Anita Oberholster
From this year cellars have been receiving the local red cultivar cross-breed, Roobernet, in commercial quantities. Due to the red juice of the cultivar, the same vinification practices that are used for other red cultivars cannot necessarily be applied. Different skin contact methods before and after alcoholic fermentation were applied to determine the effect on the phenolic and colour composition of the wine. The influence of wood treatment after fermentation is also being investigated and the wines will eventually be evaluated analytically and sensorially.
Carli Kieck
HonsBScAgric (Oenology)
The effect of wood on the quality of wine.
Supervisors: Wessel du Toit and Dr Pierre van Rensburg
The increasing use of alternative oak products such as staves, chips and wood powder has made it increasingly important to determine the optimal preparation of these products in order to produce high quality wines.
In this study we attempt to determine, by means of a fermentation experiment and a maturation experiment, the optimum wood maturation period and roasting technique for such alternative wood products, more specifically in the course of making red wine.
Wines are analysed on an ongoing basis over a six month period in terms of colour, phenolic composition and volatile flavour components. These analyses will be done by means of the spectrophotometer, HPLC and GC. The wine will also be judged sensorially.
Léan Viljoen
HonsBScAgric (Viticulture)
Determination of optimal pruning practices for two new table grape selections.
Supervisors: Mr Henning Burger and Prof. Melané Viviers
The project entails the optimalisation of pruning practices on two new table grape cultivars selected from the cultivation and selection programme at Nietvoorbij. The cultivars are a midseason, white seedless cultivar and an early, red seedless cultivar. Both cultivars will soon be released to the industry.
Quantitative evaluation of the bud fertility of the two cultivars will be determined by means of microscopic analysis of the buds as well as budding trials. A proposed pruning system will then be determined in accordance with the laboratory results. This will then be compared with actual budding percentages in the vineyard and an attempt will be made to determine an optimal pruning system for both cultivars, which will also ensure a higher yield and improved bunch quality. The influence of the pruning stage (early, mid and late) on the two cultivars will also be determined in order to initiate earlier ripening and improved bunch quality.
Marina Bruwer
HonsBScAgric (Viticulture)
Terrain identification in the Western Cape viticultural area: Plant water status and the influence thereof on the performance of Sauvignon blanc.
Supervisors: Ms Victoria Carey and Prof. Eben Archer
The world-wide surplus of wine production and increased consumer knowledge of wine places increased pressure on producers to supply a unique product.
By recognising the influence of the terroir on the performance of the vineyard block, the vineyard may be managed to attempt to influence the wine style.
Water shortage affects each aspect of the vine, if it is great enough and lasts long enough. Consequently the must composition and wine quality are influenced directly and indirectly. Both insufficient and excessive irrigation are detrimental to wine quality and the plant water status is therefore of great importance to wine grape producers.
The purpose of the project is to determine the water status of the vine at ripeness and how this influences the vegetative and reproductive performance of Sauvignon blanc.
This project forms part of a bigger study to identify natural terroir units in the Stellenbosch area.
Ronel Bester
HonsBScAgric (Viticulture)
The identification of characteristic spectra of stressed vines.
Supervisor: Prof. Melané Viviers
Hyperspectral analyses of vineyards may be used, inter alia, to observe plantphysiological changes before they are noticeable with the naked eye. More accurate and comprehensive evaluation of vineyards is therefore possible for early detection of stress symptoms so that management of variation in vineyards may be improved.
The main purpose of this study is to identify characteristic spectra for a specific stress. This will take place under controlled conditions in the hothouse where various types of plant stress will be induced and verified on a red and a white grape cultivar. The stress factors to be investigated include water stress, alkaline stress, pH and disease stress. This launch study will pave the way for the identification of stress factors under field conditions using hyperspectral distance observation.
Abraham de Villiers
HonsBScAgric (Oenology)
The influence of commercial malolactic acid inoculation cultures on rebate wine and the subsequent influence on the sensorial quality of the distillates.
Supervisor: Dr Maret du Toit
The purpose of the study is to investigate the influence of commercially available malolactic inoculation cultures on the sensorial quality of South African rebate wine and the resulting distillate.
Previous studies have already indicated the following:
Spontaneous malolactic fermentation may differ from year to year.
The sensorial quality of white wine in particular that has undergone malolactic fermentation, may differ considerably.
The malolactic acid strain may also alter the quality of the wine drastically.
The negative effect of malolactic acid fermentation on the quality of rebate wine and the distillate is caused by the different species and strains that caused the malolactic fermentation. Lactobacillus spp. was present in the less desirable distillate, while Oenococcus oeni had a more positive effect on the sensorial quality of the rebate wine and distillate.
Mareli Laker
MScAgric (Viticulture)
The effect of terroir on the water status of the vine.
Supervisors: Prof. Eben Archer, Dr Philip Myburgh and Dr Kobus Conradie
In South Africa there is limited knowledge about the indirect effect of terroir on wine quality via the influence it has on the water status of the vine. The project aims to expand this knowledge by studying the correlation between the water status of the vine, soil water status and climate. By comparing the water status of the vine with the soil water status (a function of water content and potential) and climate, it is possible to determine the extent to which the water status of the vine is a direct function of soil water status and climate.
Local research with regard to terroir studies clearly indicates that climate, topography and soil have an important influence on wine quality. Soil type and climate influence the water status of the vine, which in turn has an influence on all the physiological processes in the plant. The difference in water status among vines might explain why wines from different soil types within a terroir also have different wine styles. It is therefore important to determine which factors influence the water status of vines, and to which extent, as well as how the water status of a vine varies at different phenological stages and different times of the day. If a correlation can be proved, more accurate predictions may be made about a vineyard's reaction to a specific terroir. Information about the water status of the vine will therefore play a role in finetuning the identification of terroirs.
- Karin Theron

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