New World Winemaker Blog

“Don’t make a big monkey dance about choosing a yeast, just decide if you want esters or thiols!” This is one of the more memorable sentences that was uttered by Christoph Hammel during my recent harvest stint at his cellar in Germany. Before I put this sentence into context, I should mention that the Hammel Weingut has been in business since 1723. This proud winemaking tradition is continued by veteran and outspoken winemaker, Christoph Hammel. His skills include a combination of modern thinking, creative planning and solid experience based on many years of making wine with a scientific yet artistic touch.

Christoph is such a staunch believer in Anchor Wine Yeast, I guess that you could even call him an Anchorfile. He has repeatedly achieved success on a variety of grape varieties such as Grüner veltliner (fermented with Anchor Exotics and Anchor Alchemy I), Scheurebe (Anchor Alchemy II), Sauvignon blanc (Anchor Alchemy II), Dornfelder + Portugieser Rosé (Anchor Alchemy I and II), Müller-Thurgau (Anchor Alchemy I), Chardonnay + Weissburgunder (Anchor Alchemy I) and Sylvaner (Anchor VIN 2000), Riesling (Anchor VIN 13 and Anchor Exotics). Of special interest will be some the combinations of yeasts that Christoph likes to co-inoculate, such as VIN 13/NT 116 (also Anchor) and VIN 13/NT 116 together with Laffort X5. I have seen that these combinations have a massive effect on floral, fruity and tropical aromas, but no negative effect on fermentation kinetics.

Alex Halberstadt has the following to say about Sylvaner: “Nobody dreams about Sylvaner. Mentioning it in a group of wine people is akin to professing an interest in the finer points of cardboard fabrication. The grape bums people out.”

However, even a neutral grape variety such as Sylvaner stands to gain from these mixtures. For example, I inoculated Sylvaner with NT 116/VIN 7/X5 (as per Christoph’s instructions). Some of the tasting notes that I made over the course of the fermentation were: “tea leaf, fig, apple, floral, banana, grapefruit, spicy, curry, herbal, white pepper, grapefruit, and apricot”. In theory a more complex wine is possible because of the ester and thiol production of these yeasts and this is exactly what you’ll get in real life!

Something else that Christoph does, is oxygenation of the must and water mixture during yeast rehydration. In the photo below, you’ll see the white bin in which yeast is rehydrated and behind the bin you’ll see an oxygen tank.

Typically, the rehydration mixture is cooled down at 5ºC increments (with ample time intervals) until a temperature difference of approximately 5ºC is observed between the rehydration mixture and the must to be inoculated. Note that during all this, the rehydration mixture is continuously oxygenated by adding a steady trickle of oxygen. The rehydrated and happy yeast is then simply pumped to the tank in question. Christoph swears by this method and cannot remember the last time he suffered a stuck ferment. For more information on the science behind this, you are welcome to read my previous blog titled: “Is your yeast on sterols?”

More to follow…

Bernard Mocke is a technical consultant for Oenobrands.

Gerhard Swart, Flagstone’s winemaker, is no stranger to awards. His Free Run Sauvignon blanc has consistently received high accolades over the past years and this comes as no surprise considering the care that goes into his Sauvignon blanc.

Let’s take a closer look at how this wine is made. The Sauvignon blanc is harvested from vineyards that are 8 to 12 years old during February and March. Yield is 6 to 8 tonnes/ha. Upon arrival, the grapes are stored overnight in a cold room at 0 to 2°C. The cool grapes are then fed into the crusher under a carbon dioxide blanket. Rapidase Expression (Oenobrands), sulphur dioxide and ascorbic acid are added sequentially at the crusher. Tannin Galacool is added during crushing when Botrytis infection is evident.  The crushed grapes and juice is then pumped into a skin contact tank and kept at 2 to 4°C for 18 hours. Free run juice from the skin contact tank is pumped to another tank and skins are pumped to a Velo Evolution Press (the press was designed so that grapes can be pressed in a reductive environment of nitrogen gas). Viniclar (PVPP, Laffort) is added to the free run juice before settling. The press juice is then pumped to another tank. Fining agents such as Polylact (PVPP and casein) and gelatine are added to the press juice. Settling enzyme, Rapidase Vino Super (Oenobrands) is added at the settling tank and this lasts for 2 days at 12 to 13°C.

All Sauvignon blanc fluffy lees is combined and kept at 3 to 5°C. Total sulphur dioxide levels are kept at 35 to 40 ppm. After sheet filtration of the fluffy lees, fermentation is initiated and Turbicell is added to increase the NTU level (sheet filtration decreases this too much and can lead to nutrient deficiencies). A typical minimum NTU level of 80 to 100 is sufficient for Sauvignon blanc ferments.

Gerhard uses the following yeasts for his Sauvignon blanc ferments: Anchor Alchemy I and II (Oenobrands) contributes floral, gooseberry and tropical flavours; Anchor VIN 7 (Oenobrands) makes a big contribution towards tropical aromas; X5 (Laffort) adds boxwood, lychee and passion fruit aromas; QA 23 (Lallemand) makes a contribution similar to the Alchemy yeasts and VL 3 (Laffort) produces a waft of khaki bush. Different yeasts add complexity to the wine. Dynastart (Laffort) is added at yeast rehydration and Nutristart (Laffort) is added when needed. Thiazote (Laffort) is added in 3 stages: after 3°B has been fermented, at 16°B and at 12°B. Inoculation is done at 12 to 13°C and fermentation at 12 to 16°C. Fermentation lasts 2 to 3 weeks after which ageing on gross lees (2 weeks) and fine lees (3 to 4 months) follows. Evolution in wine aroma is monitored during fermentation and ageing by regular tasting and chemical analysis.

The Sauvignon blanc is stabilised at the end of June, bottled at the end of July and released in September. Protein stability is done after final blending, right before bottling. All Sauvignon blanc is treated with bentonite after blending.

The Free Run Sauvignon blanc sells for £10 in the UK.

Bernard Mocke is a Technical Consultant for Anchor Wine Yeast.

Nouvelle is a South African grape variety developed through hybridisation in the seventies sometime, by the late Professor Chris Orffer. The process was not conducted very scientifically and for years it was believed that Crouchen blanc and Semillon were the parents. A paternity test in 2007 however revealed that a certain mister Ugni blanc was indeed the dad. So not exactly very riveting parents but as it happens with genetics in nature sometimes, the off-spring turned out to be quite interesting and useful. It’s only really in the last 10 years or so (thumb suck) that people started to plant Nouvelle and make wine from it. Some belief it is a wine that can stand on its own. Bartho Eksteen from South African winery Hermanuspietersfontein thinks differently.

The 2010 Diner’s Club winemaker of the year feels Nouvelle is only a good blending component and uses it for his Sauvignon dominated white blend, “Die Bartho” (translated into English it is “The Bartho” and it has no relation to death). Bartho picks his Nouvelle at 19°Brix because in this unripe state it produces flavours of grass, parsley and Granny Smith apples. According to him if you pick it riper it has a waxy bubblegum aroma (almost makes you wonder why people bother with this variety). Well, grass (the type used for lawns and not the type you smoke) flavour is quite popular for South African Sauvignon blancs. Most producers seek somewhat of a green pyrazine character to balance the tropical character in their Sauvignons. Pyrazines are also common in New Zealand Savvies, as they call it.

After sorting and crushing Bartho does 48 hours skin contact at very low temperatures and therefore without enzyme seeing that it won’t work anyway. He then presses (660 L/ton yield) and add a Laffort settling enzyme and 4 – 5 g/hl PVPP, seeing that he works very reductively. He thus settles with PVPP and not ferment with it, which is apparently better. He settles for minimum 24 hours during which time he does lees rubbing – a technique where you mix the settled grape lees with the juice again to increase flavour. After racking the must is inoculated with Anchor VIN 7 since Nouvelle has Sauvignon-like characteristics and VIN 7 is a popular Sauvignon yeast in South Africa. After fermentation the wine spends some time on the thin lees and eventually forms a 9% part of the final blend of the “Die Bartho” that is 71% Sauvignon blanc and 20% Semillon. The wine is then matured in new french oak for about 5 months. It retails for £18 in the UK.

So… could Nouvelle with its grassy green character be of interest to the rest of the world’s wine producing areas?

This is a favourite claim of the so-called “natural” or “non-interventionist” winemaking movement. One of the reasons why they claim it is better to do natural fermentation instead of using commercial yeasts is that commercial yeasts with their “predictable aromatic profiles” can make, say Sauvignon blancs from Europe, taste like New Zealand Sauvignon blancs. Or worse even, it can make Chenin blanc and Ugni blanc taste like Sauvignon blanc. I have personally been in a tasting with a group of oenologists representing most of the wine countries in the world where the Germans presented a Muller-Thurgau. Everyone, including the French (much to their despair) thought it was a Sauvignon blanc. I have also once given a South African Colombard to a group of French winemakers to taste and they also believed it to be a Sauvignon blanc.

So how does this happen and is it “wrong?” The “naturalists” feel it is wrong. Winery sales figures show it is “right.” Consumers like these aromas. Wines around the world can taste similar because we make wine mostly from one specie – Vitis vinifera. Then we also use yeast which originates from mainly one specie – Saccharomyces cerevisiae. Each grape variety is not equipped with a unique set of flavour active compounds. Only the combination is unique. This combination will differ between grape varieties as well as within the same grape variety in different vineyard blocks and vintages. The main aromatic compounds found in grapes are monoterpenes, C13 – norisoprenoid derivatives, pyrazines, thiols and certain amino acids that can be converted to aromatic higher alcohols and esters. The latter two groups are non-aromatic in grapes and converted by the fermenting yeast to a flavour active form. In some cases pyrazines found in Sauvignon blanc are seen as a positive. When present in reds such as Cabernet and Merlot it is seen as a negative.

Thiols smell like guava, passion fruit, grapefruit, black currant and gooseberry. Sauvignon blanc happens to have the highest thiol precursor concentration in the grapes. Wine yeasts convert these precursors to their flavour active forms and differ in their efficacy to do so. Many other white grape varieties contain these thiols but in lower concentrations. So unless you use yeasts that are very good in expressing these aromas and combine it with certain winemaking practices, these aromas will go unnoticed – as they did for many years. However, winemakers around the world are upping their game – competition is tough. They are using modern technologies and as a result they are tapping into these flavour profiles of their grapes that they did not know exist. As a result they can sell their wine in a bottle and not a box. Is this wrong?

Yes yes stone me, I work for a wine ingredients company and I have a commercial interested in winemakers using yeast. However, my clients who’s Chenins, Colombards, Ugni blancs, Muller-Thurgaus and Verdelhos that have “Sauvignon-like” aromas are certainly not complaining about their sales. If you have very good quality grapes then you have many other flavour active compounds that can “sell” your wine for you and you don’t necessarily have to make such an effort to express the thiols. When you have less than top quality grapes, then optimising what you have is a good idea and if that means optimising thiol expression then so be it.

Just for the record – contrary to popular belief I do support natural / un-inoculated fermentations when conditions are right for it. See my earlier blogpost: Natural vs. inoculated fermentations.