Raspberry Berliner Weisse

Owen’s brew #74 and his first kettle sour, brewed in Auckland on 30 July 2026. Berliner Weisse base soured with Lactobacillus plantarum, Saaz on the hot side only, and a kilo of raspberries in late in primary so the fruit sugars ferment rather than sitting in the glass as sweetness.

The point of the additions, in his words, is floral and herbal notes “without the sweetness of adding syrup flavours to the beer in the glass”, which is the traditional Berliner service and the thing he wanted to avoid. A small charge of Vienna malt does the rest, a touch of colour and a subtle biscuity note under the acidity.

A two-stage wort

A kettle sour splits the hot side in two. First wort briefly to the boil to sterilise it, then cooled. pH came back higher than wanted, so a few more drops of lactic to bring it down, pre-acidifying giving the Lacto a head start over anything else in there. Powder from ten capsules in, covered with sanitised cling film, gently purged with CO₂, then left.

Monitored on pH rather than the clock. 3.4 after 40 hours, both a satisfactory sourness and convenient timing, so souring stopped there. Back to the boil for the brew proper, which kills the remaining Lactobacillus and locks the acidity where it is.

Fermentation

Good shake to aerate before pitching, and both packets of US-05 in, since a pH 3.4 wort is a stressful place to be a yeast cell.

Picked up after about 20 hours. Stepped up a degree a day from day 4 to day 8, then held to completion on day 11, deliberately warm and deliberately active, both to clean up any diacetyl and to make sure the raspberry sugars had healthy yeast waiting for them.

Raspberries in on day 6 with primary close to but not quite finished. That timing is the whole trick:

It was important to ensure there was still active yeast when the raspberries are added as I wanted to ensure the sugars in the raspberries were converted.

A kilo, thawed first and held in a hop bag to keep the transfer to keg clear. No need to purée them, the freeze-thaw ruptures the cell walls on its own. Bubbler picked up noticeably for about two days afterwards. Owen puts the raspberry contribution at roughly 0.5% ABV, going some way to replacing what the Lactobacillus consumed during souring.

Two figures on this page understate what happened, both for the same reason. Attenuation is derived from OG and FG, and the raspberry sugars arrived after OG was measured, so the true alcohol sits a little above it. Brewhouse efficiency left off entirely, since OG was taken after souring with part of the extract already eaten.

Cost

$82 all up, or $3.56 a litre.

How it turned out

Nice pinky-red tinge. Sourness smooth rather than bite-on-a-lemon sharp. The raspberries, Saaz and Vienna malt between them add a complexity on the nose and palate a straight Berliner Weisse would lack.

Owen’s verdict: a solid 8/10.