New World Winemaker Blog

 It used to be the drink reserved for a hot summer’s day but now consumers are increasingly turning to Rose wine throughout the year with sales up 10 per cent in the last 13 years.

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

Recently, I was in a conversation with a Burgundy wine producer whose wines I admire very much. I teased him about how reluctant Burgundians are to acknowledge somewhere on a wine label that a Bourgogne rouge is Pinot Noir (and possibly Gamay) and that a Bourgogne blanc is Chardonnay.

 ”Would it kill you to add this information somewhere on the label?” I asked.

 ”Actually, it would,” he replied, in all seriousness. “It would be the death of French wine civilization.”

 For once in my life I was speechless. I mean, here we are in the 21st century, where communication is paramount, and you’ve got the equivalent of an aboriginal wine tribe still sending smoke signals.

 What is it about wine that makes so many otherwise intelligent, interesting and ambitious people cling to habits and patterns that simply no longer work? To paraphrase from the best-selling business book, here are “The Seven Habits of Highly Ineffective Wine People.”

The full blog…
Exploring wine with Matt Kramer of the Wine Spectator 

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