New World Winemaker Blog

During a recent overseas trip, a colleague of mine once again lamented the joys of travelling. This trip kicked off with a baggage issue that ruined her dinner. Other jolly events included fishing her phone out of a toilet, missing a train, almost being run over by an expressionless Parisian, being kicked by a drunken teenager in Lille and finally a screaming taxi driver in Montpellier. Friendly people… the French. But the inside of a fermenting tank can also be a chaotic and even deadly place for yeast.

Modern winemaking can be very stressful and winemakers are putting increasing pressure on their minuscule friends. No, I’m serous! Pressure can indeed be a limiting factor; especially where low pH and high ethanol is concerned. Trapped carbon dioxide gas not only creates turbulence in a tank, but also contributes to a gradual increase in pressure. Pressures upward of 600 kPa (6 atm) typically stop yeast growth (think secondary fermentation of sparkling wine), but not necessarily alcoholic fermentation. In the book “Wine Science: Principles and Applications” by R.S. Jackson, it is stated that a pressure of 3000 kPa (30 atm) and upwards will completely inhibit alcoholic fermentation! What hardy fellows they are, these yeasts!

The use of pressure to control or stop yeast growth is not uncommon in German wineries, but high pressures can cause other problems. Spoilage organisms such as Lactobacillus, Torulopsis and Kloeckera are less sensitive to pressure and can cause a myriad of problems. The latter micro-organism is particularly pesky, as it is quite sulphur dioxide resistant, ferments at temperatures as low as 10°C and can produce high levels of ethyl acetate and amyl acetate.

Some beer brewers postulate that higher pressures have a positive aromatic effect on their ferments, but clear guidelines during vinification have not been established. At least there are many other ways to boost aroma, so don’t be depressed.

Bernard Mocke is a technical consultant for Oenobrands

On 15 February 2013, asteroid 2012 DA14 missed earth by a mere 27,700 kilometers. This ancient 130,000 ton asteroid, spanning 45 meters in diameter, would have released the same amount of energy as a detonating 2.5 megaton atomic bomb, had it collided with the earth. It looks like 15 February 2013 was global meteor day, as a 9 ton behemoth caused widespread panic and injuries as it seared through the sky above Chebarkul, a town in central Russia. Not really cataclysmic, these events, but certainly significant enough to put the thought of mass extinction into our minds.

Not only humans (and don’t forget the dinosaurs) are subject to mass extinction. Micro-organisms are intimately sensitive to changes in their environment. Take a tank of fermenting must. The savvy winemaker will manipulate this very complex environment to suit his and the fermenting yeast’s specific needs, but under certain conditions the yeast population can very quickly become extinct.

The eventual fate of the wine yeast is death. After churning out ethanol, flavour compounds and a myriad of other chemical compounds during its usually short life, the yeast unceremoniously dies. But still their job is not done. These dead cells (lees) also have a very important role, but for now the focus will be on some of the causes of death of fermenting wine yeasts.

Temperature, ethanol concentration, osmotic stress, pH, toxins, pressure, sulphur dioxide and volatile acidity can separately or in combination make your little buddies extinct. So best you follow this multi-part blog, as the next installments will focus on the specific factors listed above.

You might not be able to dodge projectiles from outer space, but you can do a lot to keep your little fermenting soldiers happy and alive right until the end.

Bernard Mocke is a technical consultant for Oenobrands

On September 24, at the 1988 Seoul Olympic games, the rivalry between Ben Johnson and Carl Lewis came to a head when Johnson won the 100 meter sprint in a time of 9.79 seconds. Subsequent drug tests revealed that Johnson used Stanazolol, a banned substance and he was promptly stripped of his gold medal. Back in the present, after nearly a decade of alleged doping, Lance Armstrong came clean about his use of various banned substances that surely contributed to him winning seven Tour de France titles.

In 1985, German laboratories uncovered the widespread use of diethylene glycol in Austrian wines. This toxic substance (the diethylene glycol, not the Austrian wines!) made late harvest wines sweeter and more full-bodied. Jail sentences and heavy fines were handed down to key players in this scandal.

Two of my greatest passions in life are sport and wine. I therefore find it very interesting (and amusing) that both are prone to doping. As is the case in sport, a wide array of biological and chemical substances are available for use in viticulture and winemaking. Grape growers and winemakers are privy to these substances and some use them to save money, aid the winemaking process and influence the quality of finished wine.

DDT, which was once a very popular pesticide, has been banned since the early 1970’s in the USA, but reports still indicate sporadic use. Things get more interesting as we move out of the vineyard and into the cellar, so put on your doping hat. The use of sulphuric acid in winemaking (to alter pH) is illegal in South Africa, but I have a source that says that this practice is still rife. As is the addition of water to must to lower potential alcohol and increase yield. Legal alternatives are available, such as reverse osmosis and the spinning cone technique, but they do not come without a fair share of controversy. I’ve also heard of cellars (locally and international) that harvest Sauvignon blanc very green and then simply add sugar in order to get to a desired alcohol level, whilst maintaining certain green aromas.

As for alcoholic fermentation, the use of GMO yeast is completely taboo. The thing is, the world is a pretty big place, so if a certain Asian country decides to use a GMO yeast that massively boosts esters and produces less alcohol, who will know? I’ve also read an article about a commercial cellar in Europe that got caught out for using a GMO yeast that can degrade 100%of the malic acid in wine.

Excellent legal alternatives are of course available.  Oenobrands offers a focused range of nutrients, non-GMO yeasts, a world first bacterial co-inoculant and enzymes for various winemaking styles, so there is really no need to break the law. Remember, cheating is for dopes. Just ask my friend, Tiger.

Bernard Mocke is a technical consultant for Oenobrands

In the one corner, weighing in at about 1500 to 2000 producers globally, we have the organic wine movement, going head to head with the new kid on the block, the natural wine producers, of which France alone accounts for about 400 producers. So who do you back in this fight? And let us not forget the greatest contender…the conventional wine producers.

Natural wines are made with minimal technological and chemical intervention in the growing of the grapes and the making of the wine. In contrast, organic wines are defined as wines that were produced from organically grown grapes, but may be subjected to chemical and physical manipulation in the winemaking process. The argument that natural wine producers have, is that wines from conventional producers become uniform. This means that they lack specific regional or varietal character after the winemaker and all his processes and chemicals are done with them. So why are the organic producers so upset about the new natural wine movement?

Organic producers have spent the last 20 years building up the organic brand, putting effort and money into creating quality products, only to have their reputation, in their opinion, possibly tarnished by wines now labelled as ‘natural’. And how many consumers will know the exact difference between these two competitors? Natural wines usually have unusual flavour profiles and are prone to flaws and faults, including oxidation and spoilage. In addition, very little information is available on the ageing potential of these wines. To add to this, organic wine production is subject to country-specific regulation, whereas no such system exists for natural wine…not yet anyway.

So the natural wine philosophy is: ‘nothing added or taken away from the grapes, must or wine’.

Is this the future of winemaking? Is this just a passing fad? Does it have a future? Or is it a real contender?

Cue Eye of The Tiger music…

Elda Lerm is a technical consultant for Oenobrands