Wild Sour — Split Fermentation

About This Beer

Owen’s first captured wild sour. Joint project with Matt. Single 5 kg wort (50/50 Pilsner + Wheat, no hops) split 50/50 across two fermenters, each receiving a different wild culture for parallel mixed-fermentation:

• Fermenter A — “Other Half / O/H”: half of Matt’s mixed wild culture
• Fermenter B — “Rua Cultivar”: Owen’s own culture, propagated from Wild Workshop Rua bottle dregs

Status: combined and barrelled. Both halves aged to good sour/funky character, were tasted clean, then combined into one fermenter and folded into Owen’s 57L Flanders Red barrel project on 21 June 2026 — this beer became the souring engine for that barrel.

The Split-Fermentation Approach

A single wort feeding two parallel wild fermentations is an elegant way to compare cultures with all other variables held constant. Any difference in the finished beer is attributable to the wild culture.

Both at ~23 °C pitch temp, aging in a “cool room” for 3+ months minimum.

Grain Bill

5.0 kg total, all Gladfield:

• 2.5 kg Gladfield Pilsner Malt (50 %)
• 2.5 kg Gladfield Wheat Malt (50 %)

Classic Berliner Weisse template.

No Hops

Defining choice — the wild cultures (lactobacillus + Brett + Saccharomyces) carry all the character. Hops would interfere with lactic acid bacteria activity (LAB don’t tolerate iso-alpha-acids well).

Brew Day

Mash in 18 L at 65 °C for 60 min, mash out at 75 °C for 10 min. Mash pH 6.0 — a touch high but less critical for a wild sour where post-fermentation acidity is the goal.

Water additions: ½ tsp calcium carbonate, 1 tsp magnesium sulphate, 1 tsp calcium sulphate, ½ tsp calcium chloride, 5 drops 88 % lactic acid. Sparge 14 L at 75 °C with 5 drops 88 % LA.

60-minute boil. ½ tsp yeast nutrient at 10 min. No hops added.

Fermentation — Two Cultures, One Wort

Wort split 12 L into each of two fermenters. Both pitched at ~23 °C.

Day-4 Snapshot

Both halves attenuated rapidly to 1.005 by day 4. The pH split (3.4 vs 3.6) is the more interesting data point: Matt’s culture is more aggressive on early acid production. Rua may have more Brett character coming through over the longer aging phase.

Over the Months

Both halves kept drying out and acidifying, throwing good pellicles — the sign of healthy Brettanomyces activity:

The O/H half pushed further on both attenuation and acid, holding the early pattern. By the time of combination both tasted clean and fruity with a restrained, sub-lemon sourness — no off-flavours.

Where It Went

Once both halves had matured cleanly, Owen tasted each, combined them into the O/H fermenter, and added a 1 L medium-DME charge to throw CO₂ and purge oxygen from the transfer. That ~22 L of combined wild sour became the souring blend for his 57L Flanders Red barrel project — 19 L into the barrel on 21 June 2026, the balance held as reserve.

Numbers

Cost — Cheapest Captured

$24.50 total / ~$1.02 per L — the cheapest batch in the captured collection by a meaningful margin.

Driven by no hop bill, no commercial yeast, simple 2-malt grain bill.

Tasting

Tasted at combination (~4 months): both halves clean and fruity with a sharpish but restrained sourness — nowhere near as sour as biting a lemon, in line with the low pH. No off-flavours. The two were judged similar enough to blend, then carried into the barrel for long oak aging rather than packaged on their own.

Lineage

• Berliner Weisse (Kettle Sour, January 2026) — previous sour brew; kettle sour technique
• This brew — Wild Sour Split (February 2026) — true wild fermentation approach; split across two cultures
• Flanders Red 57L Barrel Project (June 2026) — where this combined wild sour ended up