New World Winemaker Blog

Karien’s comments on the hype that was made about glycerol, makes me nostalgic. Everybody was caught in the frenzy to find ways to increase glycerol in wines, and people went to extremes to achieve their goal.

 Glycerol is one of the base chemicals used to make dynamite, and the commercial production of glycerol involves yeast fermentation, where SO₂ is added constantly. To protect itself from the SO₂, yeast produces glycerol. Winemakers tried to simulate this effect by stressing the yeast during fermentation. Treatments included adding small amount of SO₂ constantly during fermentation, adding unfermented juice to wine (osmotic shock) and stressing the yeast by cooling it suddenly. Many winemakers (and some of the best) practised fermentation practices where the must was cooled to 10°C, allowed to rise to 15°, cooled quickly to 10°C, allowed to warm etc, to increase the amount of glycerol in the wine.

 All these techniques probably resulted in an increase in the glycerol concentration, but had no effect on quality resulting from the glycerol.

Most people have heard about the French paradox so I thought I’d inform you about the lesser known German paradox.  I started travelling to Germany in 2001 as a fermentation consultant to the wine industry and did so on a yearly basis until starting a family put me out of international travel for a while. I tended to visit the same people every time I went and it was fascinating to monitor their progress year after year as they started implementing what I advised. I must admit I was sometimes quite surprised / relieved at the positive effects of my advice myself.  Wines that I thought were beyond hope (some Muller-Thurgaus) were all of a sudden mistaken for a new world Sauvignon blanc! Now whether that is a good thing or not is a topic for another day. The mere fact that it went from unpalatable (in my opinion) to very pleasant indeed is what one should focus on.

In 2001 most of the cellars I visited (take note I am not generalising) fermented their whites at temperatures between 18 – 22°C. This is fine for what I call “forgiving” grapes such as Riesling. Riesling has a lot of varietal character not influenced by yeast and fermentation temperature and therefore top quality white wines can be produced at these fermentation temperatures. However, there were certain other candidates that I won’t mention by name out of fear for my safety and that of my family’s, that quite honestly were not so great. I focussed my advice on these wines, what the winemakers themselves viewed as “neutral” varieties. They were all German varieties that I had no experience in tasting so I had no idea if they were truly “neutral” or not. I decided to investigate by advising colder fermentation and more aromatic yeast strains. These winemakers gradually shifted their fermentation temperatures to between 15 – 17°C and changed to different, more aromatic, yeast strains. Some now even ferment at 13 – 15°C.

And this is exactly where the paradox set in… The wines were much more aromatic. All of a sudden the grape varieties were not so neutral after all. The winemakers loved it, the consumers loved it, their buyers loved it, I liked it, BUT they could not sell it. Why not? Because they could not pass the certification of the wines. They were refused their QBA numbers because the wines “were not typically German.” Some kept on submitting the wines for certification until they struck a “younger” panel that would then pass the wines – only just though. The irony of the situation was that these “new style” German wines would then sell out in three months!

The situation has subsequently become better and I believe it becomes easier every year for winemakers to pass their more modern style (but still identifiable as German) wines, especially in the southern wine producing areas. But it certainly is a very strange and frustrating position to be in – to struggle to get certification for your better quality wine. A paradox indeed.

The choice of yeast strain used for S. blanc production has a big influence on the final aroma profile and wine quality. So depending on personal style, regional style, country style, styles your consumers prefer, style your grape quality allows you to produce – different winemakers use different yeasts to aid them in achieving this desired style. I decided to ask a few winemakers to share their fermentation secrets with me.

• VIN 7 is used for its production of gooseberry, passion fruit and grapefruit aromas. Fermentation is conducted between 11 – 14°C at a sugar drop of about 1 – 2°Brix per day.
• VL3 is used for its production of similar type aromas as well as more of a green fig contribution. It also produces very good mouthfeel and “respects” the pyrazines / green aromas. It is fermented at slightly warmer fermentation temperatures of 13 – 15°C.
• Alchemy II has a similar profile to VIN 7 but with more esters – thus a “sweeter” profile. Erika uses Alchemy on the vineyard blocks she feels need a little bit of an “ester” boost.