IGWS 2017 Annual Report

- 20 Aug 2018

In January 2017 the IGWS’s fifth anniversary was celebrated by the South African table grape and wine industries, Stellenbosch University, the initial donors: Dr Johann Rupert - Reinet Foundation, Vinpro and Sanlam, as well as many distinguished guests. This collaboration between the table grape and wine industries and Stellenbosch University is a model partnership that is delivering results that will have a far reaching impact going forward. 

Seven platforms were established and various human resources employed in order to drive a focussed approach to achieve the initial objectives set. The results of the seven platforms are clearly illustrated in this report, delivering results via excellently trained graduates and postgraduates, internationally peer reviewed publications and various knowledge transfer initiatives. The team is not looking backwards, but are focussed with energy on the future to be innovative and forward-thinking to ensure Stellenbosch University and the table grape and wine industries are at the forefront of teaching, research, innovation and knowledge transfer.

Which yeast?

Karien O’Kennedy - 17 May 2018

The two most important considerations for an optimal fermentation are: The yeast must have the ability to ferment to dryness in the given conditions without becoming sluggish or stuck and within the time frame required for process optimisation; and the sensory profile of the yeast must complement and promote the varietal character of the grapes. These two aspects go hand in hand. However, the yeast’s fermentation capabilities are always more important than its aromatic profile.

How to handle high sugar musts

Karien O’Kennedy - 17 May 2018

Yeasts are living organisms and therefore have specific genetic capabilities and limitations. Here are a few guidelines on how to handle high sugar musts to increase one's chances of obtaining dry wines.

Spontaneous fermentation: How to handle the new-old kid on the block

Debra Rossouw - 17 May 2018

Interest in spontaneous fermentation is rising in wineries across the globe. This trend has various drivers, importantly consumer preference for a perceived ‘natural’ product, financial factors (no inoculation of pricey starter cultures) and quality considerations. For winemakers considering a first foray into spontaneous fermentation, here are some helpful hints to guide you on your journey.

Yeast nutrition during fermentation

Karien O'Kennedy - 17 May 2018

Yeast nutrition is added to fermentation primarily to ensure the completion of fermentation and to limit the formation of sulphur-like off odours. It is a fairly common practice seeing that grape juice often contain insufficient nitrogen. There are five types of yeast nutrition available on the market: basic yeast nutrition (mainly inorganic nitrogen – DAP), complex yeast nutrition (inactivated yeasts, inorganic nitrogen), rehydration nutrition (inactivated yeasts), organic yeast nutrients (inactivated yeasts) and yeast cell walls. Technically, yeast cell walls have no nutritional value but rather serve as detoxifying agents. The type and dosage of yeast nutrients needed depends various factors.

Management of grapevines during drought periods

IGWS - Lucinda Heyns - 21 Feb 2018

This document highlights a few practical guidelines for managing vineyards during drought conditions. Always bear in mind that these are merely guidelines and vineyard practices should be tailored to the specific area, climate, soil type and wine goal.

Image: Lucinda Heyns

Grapevine Trunk Diseases & Pruning Wounds

Lucinda Heyns - 19 Feb 2018

Questions and Answers information sheet about Grapevine Trunk Diseases and how you can protect and treat vineyards and pruning wounds.

Image: P.G. Goussard 

Guava tree and cat's pee

Carien Coetzee - 02 Feb 2018

This manuscript focusses on volatile thiols in wine that are important compounds contributing to the varietal character of especially Sauvignon blanc wine. These sulphur containing compounds are one of the main reasons for the success observed in Marlborough Sauvignon blanc, with concentrations soaring to levels we can only dream of in South Africa. They are, however, not limited to one variety and significant contributions have been observed in other varietals such as Riesling, Colombard, Semillon, Cabernet Sauvignon and Merlot.  Research conducted at Stellenbosch University involves screening South African Chenin blanc wines to investigate the impact of volatile thiols on the characteristics of this varietal. So far, preliminary results look promising and could affect the way in which this variety is handled in the vineyard and cellar. However, to date, Sauvignon blanc has enjoyed the most attention when it comes to these potent molecules, due to the fact that large quantities can be found in wines made from this cultivar.

2.1 Recognizing grapevine leafroll disease symptoms in South Africa: Red-berried cultivars

Image: G. Pietersen, ARC-PPRI - 17 Jan 2018

Grapevine leafroll disease is quite easily observed on infected, commonly planted red-berried cultivars (Cabernet sauvignon, Merlot, Shiraz, Pinotage, Cabernet franc) from véraison onwards in the growing season.  The symptoms become more pronounced as the growth season starts to end (April-May). Symptoms tend to start on the oldest leaves at the base of cane and move upwards during the season. The earliest signs of leafroll infection are red areas with indistinct borders that form on leaf tissue in between the veins.

Could you clarify?

Jaime Gray and Malie McGregor - 02 Oct 2017

The clarification of white grape musts prior to alcoholic fermentation has long since been considered a necessary step in the production process of high quality white wines. With the unavoidable input of time, energy and/or money into the clarification process and the recent interest in trendy “dirty ferment” white wines, one is prompted to ask: why clarify at all?

A comparison between cold settling and flotation on white wine quality

Karien O'Kennedy - 04 Sep 2017

During the 2017 harvest season an experiment conducted at Groot Constantia by winemakers Boela Gerber and Rudolph Steenkamp, revealed that flotation does not harm white wine quality in any way. In fact, the wine from the tank that was clarified via flotation was incorporated into Groot Constantia’s premium Sauvignon blanc blend, whilst the settled tank’s content was assigned to the standard blend.

IGWS 2016 Annual Report

- 20 Jun 2017

Another year has passed and it is hard to believe that the IGWS is already in its 4th year of existence. The IGWS have made tremendous strides since its inception in 2013 and if one reflect over the four year period it is commendable to see the progress achieved. This is evident in the outputs achieved in all of the platforms as well as the closer collaboration between the SA wine industry and academia on various exciting initiatives.

The year started off with a bang and all hands were on deck focusing on the structural repositioning of the Department of Viticulture and Oenology (DVO), the Institute for Wine Biotechnology (IWBT) and the IGWS. There was a strong commitment from all involved in the process and it is my belief that the whole environment, as well as industry will benefit tremendously because of the outcomes of this process.

IGWS 2015 Annual Report

- 23 Aug 2016

The IGWS moved out of the starting blocks and is well on the way to fulfil its Phase one mandate, which is to enhance capacity for research, teaching, innovation and technology transfer within the Department of Viticulture and Oenology at Stellenbosch University. Overall progress is satisfactory and the broader vision is still to expand to other critical role players/partners who provide research and training services and support to the SA wine industry. The platforms each crafted a strategic document outlining their unique strategic intent and provided the detail as to how these goals would be achieved.

Guidelines to reduce smoke taint in grapes and wine

By: Karien O’Kennedy - 17 May 2016

Harvesting grapes from vines that have been exposed to bushfire smoke can result in wines containing smoke taint, commonly described as having “smoky, burnt and ash” aromas and “cigarette, ash tray, acrid and metallic” flavours. It is believed that smoke particles and associated aroma compounds enter the vine by absorbing onto the protective waxy cuticle layer or moving into the stomata on leaves and thereafter finding their way through the phloem into grapes.


Rootstock Cultivars

Prof Eben Archer - 03 May 2016

An overview of the characteristics of South African rootstocks by Prof Eben Archer. 

Currently only available in Afrikaans

Harvest Book

Practical guidelines by Karien O'Kennedy - 22 Apr 2016

Welcome to the first addition of the harvest book - printed January 2015. The book contains practical guidelines on yeasts, bacteria, yeast nutrition, enzymes and tannins. Please take note that this book is bilingual (English + Afrikaans). 

Thank you!

You have successfully signed up.

Thank you!

Your post has been sent for moderation.