Contents

• Research and focus areas
• Publications

Research and focus areas

The main objective of the research activities within the DVO is to contribute to enabling the South African industry to produce wines and vineyard products of a high quality with the aid of environmentally friendly technology in the most cost-effective manner. Industry-linked research that can be implemented by means of technology transfer to the industry is undertaken at all times.

Research activities according to the niche fields of the academic staff of the DVO, as well as the Institute for Wine Biotechnology, are as follows:

# Involved in both the DVO and Institute for Wine Biotechnology (IWBT)
* From the IWBT

Viticulture

Mr Albert Strever

Specialisation: Grapevine cultivation
Focus area: Plant management and remote sensing
His research is focused on the use of remote-sensing technology for monitoring variations in vineyard blocks (multispectral), as well as for determining certain plant physiological aspects (hyperspectral) of the grapevine. The use of remote sensing in “terroir” studies is investigated, with the emphasis being on the layout of experimental plots, as well as on a study of the genotype x environment interaction. An attempt is also made to determine certain components in the grapevine plant, for example chlorophyll and leaf nutrient status, by means of non-destructive methods, as well as to determine canopy properties (canopy density, canopy volume and leaf surface) by using remote sensing and other non-destructive techniques. Destructive techniques are then used to test the effectiveness of these methods.

Dr Victoria Carey

Specialisation: Grapevine terroirs
Focus area: Terroir characterisation and identification
The physical environment of the grapevine has a significant effect on the composition of wine grapes and on the final wine style and wine quality. This interaction is known as “terroir”. Research is currently being conducted to formulate a method for the identification of viticultural terroirs with the aid of geographic information systems. In addition, the influence of the physical environment, and particularly of climate, on vineyard performance and wine quality and character is quantified.

Prof Alain Deloire

Specialisation: Ecophysiology of grapevine berry composition
Focus area: Grapevine physiology and berry ripening
Managing harvest potential of grapes to obtain a desired wine style is complex. The first step requires a scientific understanding of grapevine functioning in its environment (mainly in relation to influences of light, water, temperature and wind). Physiological and biochemical studies with regards to the plant’s source-sink relationships and the dynamic of berry development and ripening enable us to develop a comprehensive understanding that assists in the definition of practical rules for vineyard management. Decision-making tools and indicators of plant functioning which are derived from research, are necessary to help professionals to make a decision at vineyard level.

Prof Piet Goussard

Specialisation: Propagation, cultivation and improvement of grapevines
Focus area: Plant material
His research activities are closely linked to his fields of specialisation in teaching and are based on the optimisation and reproducibility of the induction, maintenance and augmentation of embryogenic callus in various wine grape and rootstock cultivars. The aim is multidisciplinary approaches in order to apply embryogenic cell lines and/or regenerated embryos for transformation with specific genes. The main objective is to regenerate transgenic plants that offer resistance to re-infection with harmful viruses once these plants are established in vineyards.

Prof Kobus Hunter

Specialisation: Grapevine physiology
Focus area: Grapevine cultivation and metabolism
Research is aimed at the integration of grapevine physiology, cultivation, and grape and wine quality. The main point of interest is the study of vine physiology, particularly the understanding of source:sink ratios (communication and control), canopy and root system dynamics, and grape development and composition, and the interaction of these with short- and long-term cultivation practices and the environment. Focus is on the establishment of practically applicable principles to improve grape and wine quality. Attention is also paid to the improvement of plant material and the effect of cultivation practices and the environment.

Mr Pieter Raath

Specialisation: Table grape production
Focus area: Table grape cultivation and nutrition
Research addresses aspects relevant to the table grape industry. The focus falls on improving table grape quality and levels of production. Investigations into the physiological development of Thompson and Red Globe berries are conducted. The aim is to understand the factors promoting crispy grape berries and to incorporate them in a vineyard management strategy. The impact of gibberellic acid applications on vine fertility and the physiology of berry colour development are also being addressed.

Ms Erna Witbooi

Specialisation: ____
Focus area: _______
Research addresses ________________________.

Grapevine molecular biology and biotechnology

Dr John Moore

Specialisation: Grapevine biochemistry and metabolism
Focus area: Grapevine biotechnology
His research area forms part of the Grapevine Biotechnology Programme (within the framework of the NRF-supported Wine Science Research Niche Area (RNA)) of the IWBT in collaboration with Professor Melané Vivier. The goals of the programme are to improve the disease resistance, fruit quality and abiotic stress (i.e. drought) tolerance of Vitis vinifera (grapevine) cultivars utilising transgenic technology. His specific research aims are to understand the biochemical and metabolic aspects of berry development, plant pathology and abiotic stress tolerance in grapevine, with a focus on the role of the cell wall. He also maintains an interest in the chemistry and biology of plant polyphenols, with particular reference to their functional significance in planta as well as being key constituents of grapes and wine.

Prof Melané Vivier

Specialisation: Grapevine molecular and cellular biology
Focus area: Biotechnology product development and molecular biology of grapevine stress
Her research programme is focused on the biology of grapevine (Vitis vinifera). The genetic potential and molecular mechanisms underlying V. vinifera's reaction towards some of the biotic and abiotic stresses typically appearing in vineyards are studied. Two main themes form part of the programme: (i) Understanding and manipulating disease resistance and (ii) Metabolic engineering of grapevine towards enhanced abiotic stress resistance and improved quality parameters. The programme is supported by grapevine transformation and regeneration technologies, basic molecular biology and some systems biology technologies and an increasing list of analytical methods to evaluate grapevine and model plant tissues.

Dr Philip Young

Specialisation: Grapevine molecular biology and biotechnology
Focus area: Molecular biology of grapevine, with the focus on carotenoid biosynthesis
The main focus of the grapevine biotechnology research programme is on the development of genetically improved grape cultivars with outstanding fruit quality, reduced susceptibility to diseases, pests and other stress conditions, and an increased nutritive value (in the case of table grapes). The specific focus of this research is the contribution of the carotenoid biosynthetic pathway to these aspects of grape quality, especially with reference to their role in flavour and aroma development and abiotic stress tolerance.

Oenology and wine biotechnology

Prof Florian Bauer

Specialisation: Wine biotechnology
Focus area: Molecular and cellular biology of yeast
His research portfolio is focused on the yeast Saccharomyces cerevisiae and investigates the molecular processes that regulate gene expression, carbon flux (ethanol yield and transfer of activated acyl residues), aroma compound production and cellular adhesion properties. The research projects make use of all standard microbiological and molecular biology techniques, as well as genomics-, transcriptomics- and metabolomics-based approaches. Insights gained from these projects are applied to improve wine yeast strains through the use of traditional breeding, mutagenesis, directed evolution and genetic engineering.

Dr Benoit Divol

Specialisation: Wine microbiology and biotechnology
Focus area: Enzyme production by wine yeasts; molecular biology of lactic acid bacteria; interactions between microorganisms
His research focuses on three main fields: enhancing enzyme production by wine yeasts, understanding microbial interactions in order to control spoilage, and understanding the positive contribution of wine lactic acid bacteria during malolactic fermentation. The addition of enzymes has become a common step during the winemaking process. We aim to unravel and enhance the production of enzymes by Saccharomyces cerevisiae or other wine yeasts during alcoholic fermentation by means of genetic engineering tools or co-inoculation. Malolactic fermentation is a major step of the winemaking process, even though it remains poorly understood. Moreover, most of the starter cultures used by the winemakers are not adapted to South African wines. We aim to understand the influence of South African conditions on the efficiency of malolactic fermentation and the production of aroma compounds by Oenococcus oeni . Another aspect of the work is to understand the dominance of Oenococcus oeni and Lactobacillus plantarum after alcoholic fermentation through their potential production of bacteriocins.

Prof Maret du Toit

Specialisation: (i) Wine microbiology (oenology) and (ii) wine biotechnology
Focus area: (i) Lactic acid bacteria, microbial spoilage and MLF and (ii) Molecular biology of lactic acid bacteria
Microorganisms form an integral part of the winemaking process and can have a positive or negative influence on wine quality. Lactic acid bacteria (LAB), especially O. oeni, are responsible for malolactic fermentation in wine. Apart from performing this fermentation, they can also contribute to wine aroma compounds that will improve wine quality. The focus is on the following enzymes; ß-glucosidases, esterases, glucanases, proteases and phenolic acid decarboxylases. LAB is also regarded as a spoilage microorganism and the focus is on bitterness, biogenic amines and volatile sulphur compounds. LAB also produce bacteriocins, which are investigated in terms of being used as an alternative to chemical preservatives, and we also focus on lysozymes that may be used in winemaking. Research is currently being conducted on the omics of wine LAB, especially the metabolome produced by commercial MLF starter cultures. Furthermore, infrared spectroscopy is evaluated as a rapid tool with which to identify wine microbes.

Dr Wessel du Toit

Specialisation: Wine chemistry
Focus area: Wine ageing, oak aroma, wood and phenolics, oxidation
The changes undergone by red wines in wooden barrels change the style and taste of the wine, as well as its quality. Research is currently being conducted to determine the effect of this on red wine, as well as to find alternative wood maturation products. Micro-oxygenase, whereby small quantities of oxygen are added to the wine to hasten desirable polymerisation reactions, is closely related to this. Oxygen additions to red wine at different winemaking stages are also investigated. Fundamental oxidation reactions between O2 , SO2 and phenolics are investigated, and this will support the more applied research. The phenolic composition of different vineyard blocks, and how this reflects in the corresponding wines, is looked at. This will provide a large database for the colour and phenolic development of South African wines. Reductive and oxidative treatments of Sauvignon blanc juice is also investigated.

Ms Marianne McKay

Specialisation: Wine chemistry
Focus area: Wine ageing, wine and oak aroma and sensory evaluation
Previous research focused on identifying and quantifying white oakwood aroma compounds. The present project studies wine ageing, particularly issues regarding the longevity of South African (and all hot-climate) wine and key relationships between contributors such as oxygen, sulphur dioxide and acidity. The project also involves developing methodologies (chromatographic, spectral and sensorial) to assist in the analysis of the chemical composition of wine.

Prof Pierre van Rensburg

Specialisation: Wine biotechnology
Focus area: Molecular biology of yeasts
Wine yeasts ( Saccharomyces cerevisiae ) cannot degrade/utilise polysaccharides and certain grape must proteins and are also not able to destroy contaminating spoilage organisms. For these reasons, most winemakers add enzyme preparations (pectinases, glucanases, hemicellulases, proteases) and bentonite to remove filter-blocking, polysaccharide-rich particles and haze-forming proteins from the must, as well as chemical preservatives to prevent wine spoilage. However, these practices are cost-ineffective, time-consuming and contrary to the principle of environmental friendliness. Therefore, attempts are made in this laboratory to isolate new yeasts, prepare mutants and generate hybrids that will secrete these polysaccharide-degrading enzymes during fermentation. In addition, heterologous pectinase, cellulase, xylanase, protease and chitinase genes are cloned from other microorganisms, manipulated and then expressed in wine yeasts. In all of these projects, sophisticated recombinant DNA techniques are finely interwoven with the strong genetic system of S. cerevisiae in the search for answers to questions in basic biology, but also with the aim of establishing industrially applicable and improved processes.

Mr Riaan Wassüng

Specialisation: Cellar technology
Focus area: Winemaking and wine apparatus
He is responsible for the basic management operations and maintenance of the Welgevallen Cellar, including the production and ageing of wines for the Department and for third-party (external) clients. He is involved in the education of under graduate students and providing assistance to postgraduate students regarding cellar technology and wine practices. Assistance is given to research projects conducted at Welgevallen Cellar (e.g. micro-oxygenation (doctoral project) and barrel ageing experiments (undergraduate)).

Analytical chemistry

Prof Marius Lambrechts

Specialisation: Analytical chemistry
Focus area: Advanced chemical-analytical techniques in viticulture, oenology and biotechnology
His research focuses on the optimisation of the brandy process. This includes the study of the aroma components as well as the corresponding sensory quality. The effects of cultivar, time of harvesting, yeast strain and the age of the barrels used for maturation are investigated. This information is used to determine which of the above factors are important to quality. Lastly, the project attempts to determine which aroma compounds are important and to explain stylistic differences. Further research looks at the optimum ripeness of Cabernet Sauvignon grapes in relation to wine quality. This project focuses specifically on the development of phenols as an indicator of optimum ripeness. Various other parameters are also investigated.

Dr Helénè Nieuwoudt

Specialisation: Analytical chemistry
Focus area: Advanced chemical-analytical techniques in viticulture, oenology and biotechnology
Her research focuses on both the quantitative and qualitative profiling of grape and wine composition. The development and optimisation of rapid analytical techniques, particularly Fourier transform mid- infrared and near-infrared spectroscopy, form the cornerstone of the work. Multivariate data analysis, also referred to as "chemometrics", is applied to spectroscopic, chemical-analytical and sensory data in order to establish profiles of South African grape cultivars and wine styles.

Dr Anita Oberholster

Specialisation: Analytical chemistry
Focus area: Advanced chemical-analytical techniques in viticulture and oenology
Her research focuses, among others, on phenol chemistry; the development of phenols during grape ripening, changes in phenol composition during winemaking and ageing, as well as the influence of wood and macro-oxygenation. The polymerisation reactions that take place during ageing and the influence thereof on the mouth-feel properties of wine are of specific interest. The development and optimisation of analytical techniques for the quantitative analysis of phenolics and other wine components is an important inclusion.

Back to top

Publications

Publications since 1995

See complete list here

Publications of last five years

2009

Carey, V.A., E. Archer, G. Barbeau & D. Saayman. 2009. Viticultural terroirs in Stellenbosch, South Africa. III. Spatialisation of viticultural and oenological potential for Cabernet Sauvignon and Sauvignon blanc by means of a preliminary model. Journal International des Science de la Vigne et du Vin. 43(1): 1-12. [PDF]

Oberholster, A., I.L. Francis, P.G. Iland & E.J. Waters. 2009. Mouthfeel of white wines made with and without pomace contact and added anthocyanins. Australian Journal of Grape and Wine Research 15: 59-69. [PDF]

2008

Bindon, K.A., P.R. Dry & B.R. Loveys. 2008. Influence of partial rootzone drying (PRD) on the composition and accumulation of anthocyanins in grape berries ( Vitis vinifera L. cv. Cabernet Sauvignon). Australian Journal of Grape and Wine Research 14: 91-103. [PDF]

Carey, V.A., D. Saayman, E. Archer, G. Barbeau & M. Wallace. 2008. Viticultural terroirs in Stellenbosch, South Africa. I. The identification of natural terroir units. Journal International des Science de la Vigne et du Vin. 42 (4): 169-183. [PDF]

Carey, V.A., E. Archer, G. Barbeau & D. Saayman. 2008. Viticultural terroirs in Stellenbosch , South Africa. II. The interaction of Cabernet Sauvignon and Sauvignon blanc with environment. Journal International des Science de la Vigne et du Vin. 42 (4): 185-201. [PDF]

Cloete, H., E. Archer, V. Novello & J.J. Hunter. 2008. Shoot heterogeneity effects on Shiraz/Richer 99 grapevines. II. Physiological activity. South African Journal of Enology and Viticulture 29: 1-8. [PDF]

Cloete, H., E. Archer, V. Novello & J.J. Hunter. 2008. Shoot heterogeneity effects on Shiraz/Richer 99 grapevines. III. Leaf chlorophyll content. South African Journal of Enology and Viticulture 29: 9-12. [PDF]

De Beer, D., E. Joubert, J. Marais, W.J. du Toit, B.A. Fourie & M. Manley. 2008. Characterisation of Pinotage wine during maturation on different oak products. South African Journal of Enology and Viticulture 29: 39-49. [PDF]

Human, M.A. & K.A. Bindon. 2008. Interactive effect of Ethephon and shading on the Anthocyanin composition of Vitis vinifera L. cv. Crimson Seedless. South African Journal of Enology and Viticulture 29: 50-58. [PDF]

Smit, A.Y., W.J. du Toit & M. du Toit. 2008. Biogenic Amines in Wine: Understanding the Headache. South African Journal of Enology and Viticulture 29: 109-127. [PDF]

2007

Bindon, K.A., P.R. Dry & B.R. Loveys. 2007. Influence of plant water status on the production of C13-norisoprenoid precursors in Vitis vinifera L. cv. Cabernet Sauvignon grape berries. Journal of Agricultural and Food Chemistry. 55 :4493-4500. [PDF]

Du Toit, W.J., K.L. Lisjak, M.A. Stander & D. Prevoo. 2007. Using LC-MSMS to assess glutathione levels in South African white grape juices and wines made with different levels of oxygen. Journal of Agricultural and Food Chemistry. 55: 2765-2769. [PDF]

Ristic, R., M.O. Downey, P.G. Iland, K.A. Bindon, I.L. Francis, M. Herderich & S.P. Robinson. 2007. Exclusion of sunlight from Shiraz grapes alters wine colour, tannin and sensory properties. Australian Journal of Grape and Wine Research. 13:53-65. [PDF]

2006

Du Toit, W.J., J. Marais, I.S. Pretorius & M. du Toit. 2006. Oxygen in must and wine: A review. South African Journal of Enology and Viticulture 27: 76-94. [PDF]

Du Toit, W.J., K.L. Lisjak, J. Marais & M. du Toit. 2006. The effect of micro-oxygenation on the phenolic composition, quality and aerobic wine-spoilage microorganisms of different South African red wine s. South African Journal of Enology and Viticulture 27: 57-67. [PDF]

Ferreira, J., M. du Toit & W.J. du Toit. 2006. The effects of copper and high sugar concentrations on growth, fermentation efficiency and volatile acidity production of different commercial wine yeast strains. Australian Journal of Grape and Wine Research 12: 50-56. [PDF]

2005

Deloire, A., E. Vaudour, V. Carey; V. Bonnardot & C. van Leeuwen. 2005. Grapevine responses to terroir: a global approach. Journal International des Science de la Vigne et du Vin. 39 (4): 149-162. [PDF]

Du Toit, W.J., I.S. Pretorius & A. Lonvaud-Funel. 2005. The effect of sulfur dioxide and oxygen on the viability and culturability of a strain of Acetobacter pasteurianus and a strain of Brettanomyces bruxellensis isolated from wine. Journal of Applied Microbiology 98: 862-871. [PDF]

Meyer, A.H., A. Botha, A.J. Valentine, E. Archer & P.J.E. Louw. 2005. The occurrence and infectivity of arbuscular mycorrhizal fungi in inoculated and uninoculated rhizosphere soils of two-year-old commercial grapevines. South African Journal of Enology and Viticulture 26: 90-94. [PDF]

Mortimer, P.E., E. Archer & A.J. Valentine. 2005. Mycorrhizal C costs and nutritional benefits in developing grapevines. Mycorrhiza 15: 159-165. [PDF]

Back to top