18 August 2019
Sometimes an experiment seems to appear out of nowhere. In this case, I was planning to make a shaken not stirred yeast vitality starter to make sure the yeast I’d carried around for ten days in Europe’s heatwave was still viable (it wasn’t). As such I had in hand some malt extract, and the impetus struck to make up an extra gallon of wort beyond the litre I needed and play a little.
Now one of the beers which made some impact on me during that Eurpoean trip was a gose I drank in Haarlem, just outside Amsterdam, a limited 2019 release of this beer. It was a light, subtle, sparkling draught with a slight acididity and a moreish saltiness. Just perfect after a walk around town on a sunny afternoon. And so I’d been thinking about the style a bit, and about brewing one - and I’d been reading up on kettle-souring as a result.
Lacking a pure lactobacillus culture, but being a regular sourdough baker, my mind had been turning over the idea of using sourdough culture for the souring. I’d just refreshed my starter after the trip and it was bubbling away on the counter. There was the spark. I figured I could use this as a trial run towards that sourdough kettle sour.
I drew off the liter I needed for the vitality starter and got that going. And then I brought the extra gallon of wort to the boil, dropping in 10g of Hallertau Tradition to give this somewhere around 20-25 IBUs of bitterness. When the boil finished, I realised I’d ended up with too little wort (and the gravity was 1.067) - maybe this was boil-off, but more likely a screw-up in measuring something. Anyway, topping up with water gave me my gallon of wort at 1.040. Just what the doctor ordered.
The next decision was pitching temperature. I settled on pitching at around 30C and letting it ferment at room temperature. That would allow the lactobacillus to get to work - though it could also lead to off-flavours from the saccharomyces. Still, that was the plan. After cooling as best I could in the sink (I didn’t have any ice), I finished off the temperature drop in the freezer, and pitched approximately 4 tablespoons of ripe liquid sourdhough about an hour later.
I left the brew in my basement which is currently around 25-30C. The next morning it was bubbling away, and there was a good krausen by afternoon (less than 24 hours after brewing). The real test, of course, is a week or so from now.