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Suregork Loves Beer

Beer Reviews, Homebrew, Rambling

Physicochemical analysis of Sahti

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Last summer, me and a couple of colleagues visited the 23rd National Championship in Sahti brewing, which was organized in northern Espoo. The purpose of our visit was not to compete or just drink Sahti, but rather we were there to collect samples for a research project: we had decided it was time that a thorough physical and chemical analysis on Sahti was to be performed.

First of all, what is Sahti? Well, Sahti is a traditional farmhouse beer that has been produced and consumed in Finland for centuries. The Sahti beers that I have tried have all been sweet and alcoholic, with strong yeast tones in the flavour. The aroma of isoamyl acetate (banana) has particularly stood out. If you are interested in a more thorough introduction, then you can head over to this blog. For instructions (in Finnish) on how to make your own Sahti at home, you can check out this blog.

juniper

© Nesster / Flickr

We collected samples from 12 random Sahti at the Championships (all from different parts of the country). We then did some thorough analysis on these samples, including: ABV%, residual extract, IBU, colour, foam stability, sugar profile, organic acid profile, higher alcohol profile, ester profile, phenolic acid profile, 4-vinylguaiacol content, and finally we looked for juniper-derived components with GC/MS. We also analyzed seven commercial beers as references (one Sahti, two Pale Lagers, two Hefeweizen, and two Porters).

There was quite a lot of variation between the samples, but in general the Sahti had quite high ABV%, residual extract and ester concentrations, as was expected. The isoamyl acetate (banana aroma) concentration was really high in some of the Sahti (up to around 14.5 mg/L). Since Sahti is unhopped or lightly hopped, the bitterness values were low. Also, since Sahti is typically uncarbonated or lowly carbonated, the samples had really poor foam stability. All samples also had 4-vinylguaiacol (clove-like aroma, typically found in Hefeweizens and Belgian-style ales) concentrations above the flavour threshold. This is a presumably a result of the use of Finnish baker’s yeast. It can be concluded that Sahti indeed is a unique beer style, with some very interesting properties. I’m not that big of a fan myself, but I can understand the fascination behind the style.

You can download a pre-print version (i.e. it hasn’t been formatted yet) of the publication here.

Abstract:

Sahti, a strong, unhopped farmhouse beer flavoured with juniper is still actively brewed in rural areas in Finland. Presented here is the first comprehensive analysis of the physical and chemical properties of this unique beer style. Twelve sahti samples from the southwest of Finland were analysed and while properties varied, the beers generally had high levels of alcohol (mean = 7.9% ABV) and high residual extract (mean = 9.5 °P). Foam stability was negligible, as is typical for the style, and glycerol concentrations at 3.1 – 4.7 g/l were higher than in reference beers (commercial lager, wheat beer and porter). Both of these features may be attributed to the very high gravity conditions employed in brewing sahti beers. Bitterness levels were relatively low (3 – 13 IBU) due to the absence or moderate use of hops. All samples contained detectable levels of the clove-like compound 4-vinylguaiacol due to the use of baker’s rather than brewer’s yeast for brewing. Concentrations of higher alcohols and esters were high, with many individual aroma compounds being above the normal flavour thresholds. Results have highlighted the uniqueness of this style of beer in comparison to commercially available beers and have contributed to our understanding of the reasons for the particular sensorial properties of this traditional beer style.

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