Diemersdal Estate in Durbanville has clinched its eighth consecutive FNB Sauvignon Blanc SA Top 10 Award, this time for its pioneering Winter Ferment Sauvignon Blanc from the 2024 vintage. The Winter Ferment method, unique to Diemersdal, involves freezing Sauvignon Blanc juice at harvest and vinifying it four months later, resulting in an exceptional wine with elevated thiol levels responsible for a pronounced tropical flavour profile.
Thys Louw, sixth-generation owner and winemaker at Diemersdal considers this award a significant achievement. “Despite winning for eight years straight, receiving a FNB Sauvignon BlancSA Top 10 award is a highlight for any South African Sauvignon Blanc producer,” says Louw. “Sauvignon Blanc has become South Africa’s leading wine in local and international markets, and this success is rooted not only in its consumer-friendly flavour profile but in the exceptional quality South African producers have achieved. The FNB Sauvignon BlancSA Top 10 sets high standards through its rigorous judging, inspiring us all to showcase the best of Cape terroir.”
The Winter Ferment Sauvignon Blanc, first introduced in 2017, was born from Louw’s desire to push the boundaries of tropical expression in Sauvignon Blanc. After harvest, the grape must be frozen at -20°C, then thawed and fermented in June, creating a wine that stands out in both flavor and chemical profile. “The wine shows unique flavours and analyses unlike anything I’ve seen from Diemersdal’s other Sauvignon Blancs, particularly due to the high levels of thiols, which give the wine its signature passion fruit and gooseberry notes, similar to those in New Zealand’s Marlborough region,” says Louw.
Typically, a high thiol count in South African tropical Sauvignon Blanc measures around 2,500 nanograms per litre, but Diemersdal’s Winter Ferment boasts levels near 5,000 nanograms per litre—a remarkable feat for South Africa. “This level is rare here and was beyond my expectations for the experiment. The frozen juice yielded a wine with double the thiols and extraordinary tropical aromas,” explains Louw.
The process begins with night-harvesting the grapes at 23 degrees Balling, followed by reductive crushing and destemming. After three hours of skin contact, the juice is pressed, settled for 48 hours, and then frozen for four months. Once thawed, fermentation occurs at 14-16°C for two weeks before bottling. The result is what Louw describes as the most “New World style” Sauvignon Blanc he has crafted. “It has intense aromas of gooseberries, tropical fruits, and sweet grapefruit, with a mineral core. The rich fruit expression is beautifully balanced by the wine’s natural acidity, giving it a full, textured mouthfeel.”
Since its release, Winter Ferment has garnered both critical acclaim and commercial success. “What started as an experiment has become a beloved addition to the Diemersdal range,” says Louw. “Winter Ferment represents Diemersdal’s commitment to exploring the full potential of Sauvignon Blanc, adding new layers of complexity and depth to the variety. As for what we’ll try next, we’re always ready to explore new possibilities. The wine world holds endless excitement, as Winter Ferment has proven.”
