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A week in a bucket: wild-fermenting 41 kilos of Solaris without adding yeast
Riper fruit than Sussex usually gives, a pied de cuve made from the same rows, and one bad-egg morning on day four. Here is the full log, reading by reading, from crush to dry.
The Solaris came off two rows at a small vineyard outside Lewes on 21 September: 41.6 kilos in six crates, at 23.5 °Bx, pH 3.31 and a titratable acidity of 7.2 g/L. That is riper than Solaris usually gets in Sussex, and it changed the plan. With that much sugar and no added yeast, the risk isn’t a slow start. It’s a fast, hot finish that strips the aroma and leaves the wine smelling of struck matches.
Four days before picking I made a pied de cuve: two kilos of the best-looking bunches from the same rows, crushed by hand in a sterilised bucket, covered with muslin and left at 21 °C. By day three it had a cap of fine foam and smelled of apple peel and bread, which is what you want. Vinegar or nail-varnish notes mean you start again. That 1.8 litres of fermenting must went into the main batch as the inoculum, roughly 7% of the final juice volume.
Crush and press came next. We destemmed by hand (two people, ninety minutes), crushed with a hand-cranked roller crusher, and left the fruit on skins for 36 hours in a 60-litre food-grade bucket at 14 °C. Skin contact on a white hybrid is a judgement call. Solaris has thick, phenolic skins, and past 48 hours the wine turns bitter rather than textured. I pressed in a 12-litre basket press in three loads. The yield was 27 litres, about 65 litres per 100 kilos, which is normal for a basket press and a patient person.
Here are the readings, all taken by hydrometer and corrected to 20 °C: day 0, 23.5 °Bx; day 1, 22.8; day 2, 20.1; day 3, 15.6; day 4, 10.2; day 5, 6.0; day 6, 2.4; day 7, −1.0. Wild ferments usually lag for 24–48 hours while native Hanseniaspora and other non-Saccharomyces yeasts do the opening work. Then Saccharomyces takes over and the curve steepens. Days 3 to 5 are where the heat builds. A 27-litre batch in a garage won’t run away like a 500-litre tank, but mine still reached 23 °C at the core on day 4 in an 18 °C room.
Day 4 also brought the smell everyone fears: rotten egg, faint but definite. Hydrogen sulphide early in fermentation almost always means a yeast population short of nitrogen, and the cure at this stage is air and food, not copper. I racked the whole batch bucket-to-bucket with a deliberate splash, then stirred in 0.25 g/L of an organic nutrient made from inactivated yeast, 6.75 grams for the batch. By the evening reading the smell had gone and the airlock was ticking about once a second.
At −1.0 °Bx the wine is dry, or very close to it. The hydrometer reads below zero because alcohol is lighter than water. The wine has gone into a 25-litre glass carboy and a 2-litre top-up jug, both filled to the neck, and will sit on its gross lees for ten days before the first racking. No sulphite yet. That waits until malolactic fermentation either starts or is ruled out, which is next month’s log.
What I would change: I’d pick four or five days earlier, at around 21 °Bx, to keep the finished wine nearer 12% than the 13.5% this one will land at. I’d also add the first half-dose of nutrient on day 2, before the yeast has a chance to complain. The pied de cuve I would make exactly the same way again.