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An SA first: Sauvignon Blanc made from frozen juice

In search of optimum tropical fruit expression, Thys Louw from Diemersdal Estate has successfully experimented in making the first South African Sauvignon Blanc by fermenting grape must that was frozen after harvesting.

This 2017 vintage was such a success in the market that production was increased for the 2018 vintage which has just hit the market. 

The Diemersdal Winter Ferment Sauvignon Blanc was made by freezing the grape must to -20°C soon after the grapes were harvested in February. The frozen must was thawed in June this year, inoculated and allowed to ferment as per normal.

Although, according to Louw, the results of this freezing and late “winter” ferment have been anything but normal.

“For reasons unknown, the wine is showing flavours and chemical analyses I have never encountered in any of the Sauvignon Blancs made at Diemersdal,” says Louw.

“The primary feature is the high occurrence of thiol compounds. 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.”

The grapes for the Winter Ferment were night-harvested at 23B, with crushing and destemming done reductively. Skin contact of three hours was followed by pressing and the juice was allowed to settle for 48 hours after which it was frozen.

The fermentation of this wine was postponed for four months before inoculated with CKS yeast. After two weeks alcoholic fermentation at 14-16oC the wine was bottled.

Louw describes the wine as the most “new world style of Sauvignon Blanc” he has made. “The wine has intense aromas of gooseberries, tropical fruit and sweet-grapefruit with a core of minerality.

“Besides the intense fruit-expression, the excellent natural acidity creates balance to the concentrated, rich mouth-filling texture.”

Recommended retail price: R140

Source: Diemersdal