A Sauvignon Blanc made by fermenting juice that had been frozen during harvest five months earlier has led to Diemersdal Wine Estate in Durbanville being one of two finalists in this year’s Winery Innovator in the International Wine & Spirits Competition (IWSC). The IWSC is the world’s largest drinks competition annually attracting entries from over 90 countries.

Diemersdal’s Winter Ferment Sauvignon Blanc was released for the first time last year, a result of cellarmaster Thys Louw’s quest for optimum tropical fruit expression in Sauvignon Blanc. The unique wine is made by freezing the grape must to -20°C soon after the grapes were harvested in February. The frozen must is thawed during the South African winter in June, inoculated and allowed to ferment as per normal. The result is above-average thiol levels leading to a wine of superior tropical character.

“The wine’s primary feature is the high occurrence of thiol compounds,” says Louw, who this year made the second vintage of Diemersdal Winter Ferment Sauvignon Blanc. “These thiols are what gives Sauvignon Blanc the passion fruit and gooseberry flavours for which especially the wines from New Zealand have become famous for.”

Louw says that while a high thiol count for a tropical style of South African Sauvignon Blanc amounts to 2 500 nanogram per litre, the Winter Ferment Sauvignon Blanc measures in the region of 5 000 nanogram per litre.

“This high thiol level is unheard of in South Africa and is more in line with what one would find in wines from Marlborough in New Zealand,” he says. “When I set out with the idea of freezing must, I wanted to see what the effect would be on the freshness and the complexity of the wine, including a possible increase in thiols. But no way did I expect the frozen juice to deliver a wine with double the thiol level we at Diemersdal had become accustomed to and with such extraordinary tropical flavours.”

Since its release last year, Diemersdal Winter Ferment has won numerous South African accolades including two FNB Top 10 Sauvignon Blanc Awards as well as Best Sauvignon Blanc at the National Young Wine Show.

Now the wine is up for its first international recognition when the IWSC Award for Winery Innovator of the Year is announced on 14 November.

Diemersdal Winter Ferment NV