New World Winemaker Blog

This blog entry concludes my feature on what yeasts are used for Sauvignon blanc fermentations. For the “grande finalé” I decided to move abroad and focus on the German Sauvignon blanc of all Sauvignon blancs. Why? Well the winemaker has a very interesting approach to the fermentation and the result is a spectacular wine.

 

Christoph Hammel, owner of Weingut Hammel in the Phalz, is quite an opinion leader in his area. He is very open to new ideas and experimentation and it is this very experimentation that has lead him to his winning recipe on Sauvignon blanc. Christoph has 53 ha of Sauvignon blanc that he harvests on average in mid October at a sugar level of about 21.5°Brix. He does not chaptilise, which is often the case in Germany, but rather concentrates the juice with a “concentration machine” – to use his words. He does 5 hours skin contact at 5 – 10°C with an   addfood enzyme in the presence of SO₂, ascorbic acid, dry ice and un-toasted wood chips. He does not cold settle the juice but rather flotates it with Nitrogen gas. This practice is quite common in Germany . 

 

Christoph uses two yeasts for fermentation that he inoculates at the same time for a co-fermentation. They are Anchor VIN 7 and Laffort X5. The yeasts are re-hydrated in Lallemand Go-Ferm and receive three additions of DAP during fermentation. They are therefore quite well fed. The yeasts are inoculated at 15°C and fermentation temperatures are kept between 15 – 17°C.

 

Why does he use these specific two yeasts in a co-fermentation? Over the years Christoph tried various yeast blends – with varying levels of success. This blend proves optimum for his Sauvignon blanc. Both yeasts are very effective in expressing the volatile thiols associated with S. blanc varietal character. They have slightly different aromatic profiles and X5 also consumes some of the volatile acidity produced by VIN 7.

 

Towards the end of the fermentation Christoph also adds B-Glucosidase (monoterpene aroma release) and B-Glucanase (yeast autolysis) enzymes. Fermentation lasts between 11 – 14 days. The wine is kept on the gross lees for 3 – 4 months until bottling.

 

The concept of co-fermentation originated with the 2005 AWRI research on Sauvignon blanc. There are very specific guidelines one must follow before attempting a co-fermentation. A common combination for S. blanc in Australia is Anchor VIN 7 and Lalvin QA 23. Recent results from AWRI research proved Anchor VIN 13 and Lalvin QA 23 to be a good combination for Chardonnay – unpublished results. Co-fermented wines have different aromatic profiles to wines made from two tanks that were blended after fermentation with the same individual yeasts. This is due to the interaction between the two yeasts during fermentation. Co-fermentation does not always have a more positive outcome and I suggest winemakers to consult with yeast suppliers first before attempting a co-fermentation.

 

The title of this blog was used without permission from Monty Python.

Boschendal wine estate, probably one of the most picturesque wine estates in South Africa (and the world for that matter) produces three different Sauvignon blancs. With all three of these wines they try to achieve (and succeed if you ask my opinion) a more international / European style Sauvignon. They achieve this style by simply altering their fermentation conditions. As simple as that.

 

The grapes are picked on taste between 20.5 – 22°Brix. The rule is that all Sauvignon blanc grapes must be in the cellar by 12 noon to avoid the heat of the day. Winemaker, Lizelle Gerber, then adds the Laffort skin contact enzyme after which the grapes go through a mash cooler to cool them down to between 9 – 14°C. Skin contact is for 4 hours and not all grapes get deliberate skin contact. Some of the grapes only have “skin contact” the time it takes to fill the press. After pressing the juice settle for 48 hours at 10 – 12°C with an addition of Laffort settling enzyme. The juice is then racked and fine lees incorporated to achieve a final NTU of 130 on average. This is a big difference compared to the previous two producers mentioned in previous blog entries who aim for a final NTU of 50 – 80. The latter is more suitable for new world style wines and the 130 NTU is more in line with the NTU levels obtained in Europe. The reason for the 130 NTU objective is that it suits the yeast – Laffort VL3 better and it is better for mouthfeel development. According to Lizelle, mouthfeel is their main objective before aroma. In the case of typical new world wine production, aroma is usually the first objective and by decreasing NTU and fermentation temperature it helps one to achieve this objective.

 

After inoculation of the yeast the temperature rises to about 18°C and it is kept on average at about 17°C throughout fermentation. Once again this is a requirement of the yeast and is also different to the practices of the previous two producers who conducted fermentation at much lower temperatures. Boschendal does analyse for YAN before fermentation and do adjustments accordingly during fermentation. They use Lallemand Fermaid K (Laffort probably ran out of stock since they seem to like Laffort) and liquid ammonia – permitted in South Africa. Fermentation lasts between 14 – 18 days. VL3 is used mainly for its mouthfeel and tropical aroma contribution. Boschendal is not interested in emphasizing any pyrazine aromas typically associated with South African and New Zealand Sauvignon blancs.

 

The wines are kept on the gross lees for as long as the lees are healthy. After the blends are made up the wine is kept on the fine lees until stabilisation before bottling. Bottling is done on demand and usually starts in September of the same year.  The single vineyard reserve is kept on the lees longer and bottled much later.

 

The Boschendal Sauvignon blanc is a typical example of how altering your fermentation conditions can influence your wine style. It does not mean that you will all of a sudden produce a Sancerre because you ferment like Sancerre (I’m not sure how winemakers ferment in Sancerre but I suspect it is not with new world wine yeasts at 13°C). The terroir is still completely different. It does however give you a style of wine that is more appealing to the European palate but with a flair of new world freshness.

So I continue my quest to find out what yeasts winemakers use to ferment their Sauvignon blancs with. This is what winemakers Charles Hopkins and Elzette du Preez  of De Grendel winery in the Durbanville winegrowing area in South Africa do.

 

De Grendel is a private winery and 90% of their Sauvignon blanc grapes come from their own vineyards. They start harvesting S. blanc in the first week in February and continue for three to four weeks depending on the location of the vineyard and therefore its ripening times. They pick the grapes on analyses (with the aid of infrared photography of the vineyards) and experience with the specific block. The minimum sugar at harvest is 22°Brix and an acidity of about 9 – 11 g/l. This results in a final wine of about 13 – 14% alcohol with a TA of 6 – 7 g/l. No tartaric acid adjustment is therefore needed. After crushing the grapes go through a mash cooler followed by 12 – 18 hour skin contact at 8 – 10°C (47 – 50°F). They use the DSM skin contact enzyme – Rapidase Expression. Only the grapes that came in at 25°C (77°F)or lower receive skin contact. If the grapes come in at a higher temperature, the mash cooler cannot lower temperature sufficiently enough and there is the danger of extracting phenolics. The long skin contact at low temperatures also promotes natural tartrate precipitation necessary to achieve the final desired TA.

 

Settling is for 2 – 3 days in horizontal settling tanks. The juice is also circulated during this time over the lees to enhance additional flavour extraction from the lees. After settling the NTU of the juice is about 20. To achieve a fermentation NTU of about 50 – 80 some of the fine lees is racked with the juice. This is monitored very carefully. The tanks are then warmed up to 16 – 18°C (61 – 65°F) before yeast inoculation.

 

45% of the wine is fermented with Anchor VIN 7. They use this yeast predominantly on the musts that contain more pyrazine aromas. They feel the gooseberry profile it delivers balances the “green” aromas from the pyrazines. Another 45% of the wine is fermented with Anchor Alchemy II yeast blend. This yeast blend also enhances volatile thiols but also produces esters and delivers a very tropical style Sauvignon blanc that is often the preferred style in the rest of the world. The additional 10% is fermented with Anchor VIN 13, Laffort X5 and a co-inoculation of VIN 13 and Lalvin QA 23 for complexity in the final blend. Fermentations are initiated at 17°C (63°F)and after 4°Brix has fermented, brought down to 14°C (58°F).  Fermentations last for 10 – 14 days.

 

After fermentation the wine is kept on the gross lees for 100 days. The two blends are then made up and kept on fine lees until stabilisation before bottling. Bottling is done every two months starting end of June. The remaining wine is kept on the fine lees at 10°C (50°F). Throughout all the processing steps the oxygen levels in the wine are very carefully monitored to ensure a reductive environment.

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.

 

Erika Obermeyer, female winemaker of the year 2008 in South Africa and head of the South African Sauvignon blanc Interest Group has been very successful over the past few years with her Graham Beck Sauvignon blanc. Erika gets her grapes from seven different vineyards, all classified as coastal, with influence from the Atlantic Ocean. She starts tasting the grapes at 16°Brix and picks on flavour. Each vineyard delivers a specific aroma profile in the final blend. Harvest starts in the last week in January and continues for four weeks depending on the location of the vineyard. 

 

Erika uses the Laffort skin contact enzyme for 5 hours at 8 – 12°C. She has an additional 7 – 13 hours of skin contact but at very low temperatures where the enzyme is obviously not active anymore. After pressing she settles for three days and achieves a juice clarity of 20 NTU this way. This, off course, is way too clear for fermentation and she therefore includes some of the fine lees when racking the juice. Her final juice clarity for fermentation is usually between 50 – 80 NTU, which is a typical NTU for new world wine fermentations.

 

Now for the juicy part: Erika uses 50% Anchor VIN 7, 40% Laffort VL3 and 10% Anchor Alchemy II for fermentation in different tanks (not co-inoculation). The vineyard the grapes derive from determine the yeast used. She uses Lallemand Fermaid K as a complete yeast nutrient for fermentation.

 

 The wines are kept on their gross lees, which is stirred twice a week. The final blend is kept on the fine lees until stabilisation before bottling. The first release of the wine is in June of the same year. Bottling is done on demand. The rest of the wine remaining in the cellar is kept at about 4 – 7°C.