New World Winemaker Blog

During my recent harvest stint in Germany, my host, Christoph Hammel uttered many memorable (and some that I am not allowed to mention here) pearls of wisdom. He told me about a meeting where some of the biggest names in German winemaking and professors associated with the wine industry were present. A very well know professor publically stated that his belief system does not have any room for the theory that yeasts impart any aroma to a wine fermentation. At this, Christoph got up and glibly replied: “My dear sir, it is not a question of belief. It is a question of knowledge.” The subsequent pandemonium that ensued was apparently quite noteworthy (hence the photo above).

Christoph is a big believer in using technology, specifically technology that can be used to make wine, and wine processing, better. Even more specifically, he is a big believer in additions.  He always said to me that he makes wine that people want to drink and if this can be achieved with the addition of enzymes and other winemaking tools, so be it. Every addition that he does is done for a reason. One thing can be said with certainty and that is that Christoph believes in the “interventionist” approach to winemaking. A lot of winemakers like to claim that their wine is made “naturally” and with the least possible human intervention, but Christoph is at the complete opposite of the spectrum. He has some pretty far out and amazing ideas and some might even call him a renegade or a cowboy after hearing about his yeast mixing and addition regimes!

As far as the additions are concerned, Optiwhite (Lallemand) is one of his stalwarts. This is usually added at the beginning of fermentation. β-glucanase and β-glycosidase enzymes  are added at the end of fermentation (at about 0°Brix). Depending on the structure and quality of a specific wine, ascorbic acid is also added right at the end of fermentation. DAP is added at three stages and is sometimes even added in divided dosages during the day, depending on the fermentation bouquet. In addition to DAP addition, thiamine is added to all musts. This is done simultaneously with sugar addition. It is well known that fungal infection on grapes depletes thiamine and it is therefore an excellent prophylactic measurement against stuck, sluggish or smelly ferments. For each addition, a cost to benefit decision is made. For instance, light and easy drinking wines will not get all the bells and whistles. The more expensive wines will get a full range of stuff added.

If Christoph was not such an excellent winemaker, I would have said that he missed his true calling in life: A chef! A chef who is forever mixing, adding and tasting, mixing, adding and tasting…

Now you probably wonder what old Jack Sparrow had to do with this…Interestingly enough, Stinkpots, favorite weapons of pirates, were malodorous concoctions made from saltpeter, limestone, asafetida (a vile-smelling gum resin), and decayed fish that were packed into earthenware jugs, ignited, and hurled onto an enemy ship…

Most of us had to manage a stinkpot brewing in our cellar at some stage of our lives, whether it was a result of a power failure (load sharing for South African winemakers), too little nitrogen, or just a general struggling yeast population. And then of course, if the H₂S turns into mercaptans… it will just about kill any odorous component remotely smelling of fruit.

H₂S contains sulfur in its most reduced form. Mercaptans are common organic compounds. When aerated, mercaptans can be oxidized to disulfides, which slightly change their sensory threshold and character. The oxidized forms are usually less of a stinkpot. These reductive components have unpleasant odor descriptors, and these can increase post-fermentation. Some of these, such as H₂S and mercaptans, react with copper and can be removed by copper additions, usually in the form of cupric sulfate. In some wineries additions of cupric sulfate is a standard procedure, sometimes with an addition of inactivated carbon. All of us are aware of course that such an addition, particularly on Sauvignons, can reduce the concentration of aromatic thiols with up to 20%… I personally believe a slight element of H₂S might actually contribute to the complexity of Sauvignon blanc.

But what to do? Well, the magic potion arrived in the form of inactivated yeasts impregnated with copper – Reduless®. It can be suspended with water and added to the tank directly after primary fermentation. The wine is racked off the lees after 72 hours. No residues, no potential risk of copper casse forming, but only a fresh smelling, wonderful wine. It has been developed by Lallemand for red and white wines to reduce H₂S, DMS, DES and other stinkpot related off-flavors in wine.

Bertus Fourie is a winemaker, turned Enology lecturer and creator of the Barista coffee Pinotage.

Recent crackdowns on doping in sport have made all of us more aware of the effects of performance enhancing supplements. This got me thinking. What if winemakers could come up with a legal magic potion for yeast? Like the magic potion that enabled Asterix and Obelix to defeat the Romans time after time. Something that would give mere mortal yeasts super human (rather super yeast) qualities?

An increasing worldwide trend is longer “hang-time”. Delaying harvest might increase berry aroma and decrease acidity, but it creates a unique problem for our little athletes. Increased sugar leads to increased alcohol levels in wine made with these grapes. Fermenting yeast thus run the risk of being smothered in the alcohol they produce as a result of them snacking on sugar. Fortuitously, there is a magic potion that you can give your yeast to boost their viability during fermentation.

First, let’s look at the definition of sterols: “Any of various alcohols having the structure of a steroid, usually with a hydroxyl group (OH) attached to the third carbon atom. Sterols are found in the tissues of animals, plants, fungi, and yeasts and include cholesterol and ergosterol.” Here comes the interesting part. Sterols and unsaturated fatty acids (UFA’s) are survival factors during fermentation, but oxygen is needed for the synthesis of said survival factors. With insufficient amounts, the yeast cell membrane functions poorly, especially during highly anaerobic conditions and especially with increasing ethanol levels. Inadequate sterol concentrations around flux controlling proteins in the yeast cell membrane cause damage to the cell membrane and ultimately results in cell death (read: stuck or sluggish ferment!). The key role between oxygen and sterols now becomes evident. Simply put, controlled and timely oxygen addition = more sterol synthesis = better ethanol resistance = happy yeast = happy winemaker.

In my previous life, I’ve found it useful to add oxygen to red ferments anytime from a third of the way through alcoholic fermentation, up to halfway. This roughly corresponds with the end of the cell growth phase and research has shown that an oxygen addition of five to ten mg/L has a very positive effect on cell viability. Another trick is to combine oxygenation and nutrient addition with a pump-over or punchdown. Complex yeast nutrients contain inactivated yeast, which is a good source of sterols. The abovementioned trick also counteracts reductivity, which every winemaker deals with at some stage.

Research is ongoing to gain more insights into how yeast sterol uptake and synthesis affects cell viability. Ergosterol is one of the main compounds being studied, but I’ve also read a paper which outlines the addition of cholesterol to a fermentation! Fermenting yeast are just as happy with cholesterol as they are with ergosterol, but I seriously doubt if winemakers will be chucking cholesterol by the bucketful into their wholesome red wines!

Bernard Mocke is a technical consultant for Oenobrands.

Over the years, South African winemaker, Henry Kotzé, has refined his winemaking mantra to one of minimal interference and maximal expression of variety by means of selecting the best terroir possible. Experience speaks for itself and Henry was appointed winemaker at Morgenster in 2009. Previously, Henry’s oenological skills were honed during his stints at Vergelegen, Boschendal, Neil Ellis and Eikendal (all highly acclaimed South African wineries.) Henry’s focus at Morgenster is on red wine where he works with the classical Bordeaux grape varieties (Cabernet Sauvignon, Cabernet franc, Petit Verdot and Merlot) and Italian grape varieties (Sangiovese and Nebbiolo).

The first vines on the farm were planted in 1994 and the average age of the vineyards is 15 years. The grapes are usually harvested, depending on the fickle weather of course, late February. Average yield is 5.5 tonnes per hectare and juice yield is 700 litres per tonne.

Now, let’s get started with the winemaking section of this blog. This is what Henry had to say: “As the grapes are destemmed and crushed (about 10% is whole bunch pressed), I’ll add an Enartis red wine enzyme for colour extraction. Cold soaking is done for two to four days at less than 10°C. Only one pump-over a day is needed and this is done slowly and gently, to facilitate maximum extraction.” As he says this, he glances longingly at his mud encrusted mountain bike and then back to me. I realise that he’s probably very busy and has not been getting a lot of sleep (the plight of every winemaker!), so I hurry on with my questions. As for the Bordeaux varietals, Henry elaborated about two of his favourite yeasts: “I inoculate Anchor NT 202 and Anchor WE 372 (Oenobrands) at 15°C. NT 202 has always been a stalwart and works well with the wine style that we like to embrace at Morgenster. It is also easy controllable with temperature alterations.

As for WE 372, it is a slower fermenter which really enhances the varietal character of the grapes I am working with. WE 372 makes a particularly powerful contribution towards red berry and fruity aromas when I’m working with Merlot. For my Italian varietals, I use selected Lallemand yeasts. A typical fermentation is done at 26 to 28°C for seven to ten days. I also use a lot of oxygen during fermentations for maximum colour extraction. As an activator I use Laffort Dynastart and Anchor Nutrivin (Oenobrands) and DAP during fermentation.” Henry also formed part of a group of winemakers in South Africa who tried the new Anchor NT 202 Co-Inoculant MLF starter culture (Oenobrands) in 2011.

He says: “I tried the Co-inoculant on a batch Petit Verdot this vintage and was pleasantly surprised with the results, since MLF took only 14 days to complete after AF finished. This usually takes three to five weeks. I usually inoculate all my red wines with Lallemand bacteria, but intend to use the Co-inoculant again next year and in bigger amounts.” Henry explains post-AF as follows: “Extended maceration on skins can last a few days or up to two weeks. After MLF, the wine is racked and three rackings are done during 18 months of barrel ageing. Beta-glucanase (Enartis) is used during ageing.

Optimal filtering would be done with a 1.6 micron candle filter, but where VA is 0.6g/L or higher, I will use a 0.45 micron candle filter.” Henry has his wine bottled during December and January after which it is released three years later. As for the premium Morgenster wines, expect to pay US $69 and US $33 for the Lourensriver Valley range.

Bernard Mocke is a technical Consultant for Anchor Wine Yeast.