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.