After returning from a visit home to Finland, Sam brought some bottles of sahti to the brewery for us to try. It was the first taste of an authentic sahti for most of us. A sweet but strong beer with a prominent, deep rye flavor. The juniper played a background role and there are normally no hops used. This beer is popular on holidays in Finland. It's produced by craft breweries and popular with Finnish home brewers.
Sahti must be stored cold and consumed relatively quickly after it's packaged. Fermentation is arrested when it drops to 5 plato (1.020 SG) to lock in the sweetness, a process similar in port winemaking. Although with port aguardente is added to kill the yeast — in the case of sahti it's chilled to below 10°C to stop fermentation.
Sam, who works at Pyynikin Käsityöläispanimo brewery in Finland, led us through the brew day using a typical recipe. There are many small water additions to the mash, each hotter than the last to raise the temperature to make a multi-rest mash. You start with a very thick mash. Wait, no, that's an understatement — the first water addition didn't even wet half the gain. After the third or fourth addition we had enough water where we could actually stir it, and by the last we had a fairly thin mash.
Historically, juniper branches are used as a lauter filter. Since there's little juniper in Portugal and Sam didn't want to pack his luggage full of tree branches, we added juniper berries rather than branches to the mash for flavor and used our regular mash tun's false bottom as a filter.
For this style of beer you use Finnish bakers' yeast, which Sam also provided. We made a 500ml starter at the beginning of the day and added it after knockout. For the next week it fermented slowly with a consistent, snow-white krauzen the whole time. After a week we reached our target terminal gravity and moved the batch to the cold room to stop fermentation. We'll obviously need to keep the beer cold until it's consumed, since moving it back into ambient temperatures could restart fermentation.
Start with 4.5 liters of 37° water. Then: 45, 55, 70, 85 and 100°C. Short boil. Ferment at 20°C, checking gravity until 5P is reached, then chill for 24 hours, keg and serve (no carbonation needed!) Just make sure that it never gets back up to ambient temperatures: without fine filtration, the yeast could become active again and over-pressurize bottles.
Although I'm tasting each beer several weeks apart, I'm struck by how similar our version is to the samples Sam brought back. We'll have this small 20 liter batch in the tap room for others to try this Friday, February 5th.
For the unknowing public, the first sip might be a surprise. It's completely flat, cold, sweet, and 10% alcohol, things that don't usually go together, so we have to approach it with the right mind set in order to enjoy it. Sahti is what beer writer Michael Jackson said was the missing link between ancient brews and today's beer. Cheers to Sam for giving us a hand and adding a touch of Finnish authenticity to this beer.