“Uniquely, sahti production involves branches (and sometimes berries) of juniper, which adda spice flavour to the brew and have an antimicrobial effect. These branches lie on a filter bed composed of straw (rye typically) at thebottom of akuurna(a trough-shaped, aspen-hewnvessel) through which the sahti wort is filtered. The first wort prepared is the strongest and may be collected separately to the later wort. The weaker, sugar-poor wort was traditionally reserved for preparationof a mild table beer,while the stronger wort was used to ferment the full-strength sahti normally containing 7-8 % alcohol.Another unique feature of the process is the use of baker’s yeast, rather than brewing yeast, to carry out fermentation(3).”
Physicochemical characterization of sahti, an ‘ancient’ beer style indigenous to Finland (pre-print copy) – ResearchGate.

 

Sahti, an ‘ancient’ beer style indigenous to Finland