Sahti: Finland's 400-Year-Old Farmhouse Beer

The History of Finnish Brewing

The cradle of the art of brewing beer in Western Europe was Germany. In the 12th century, trade merchants spread the craft to the Baltic Sea, from whence castellans (keepers of the castles) and local tradesmen deployed it even further.

Brewing came to Finland by two distinct routes: from the south straight across the narrow Gulf of Finland, and from the west by way of Sweden. Finnish brewing was in full swing by the 1400s — these early Finns must have turned out decent beer, since in 1504 the castellan of Stockholm's royal castle preferred to procure all the beer he could from Finland. At that time, Finland was an eastern province of the Kingdom of Sweden, serving as a strategic entrenchment against the archenemy Russia. Garrisonlike castles, with surrounding towns, were built in various localities of strategic importance. Because these towns were hundreds of kilometers apart and a typical day's journey by horse in the summertime was around 19–25 miles (30–40 km), a network of inns and royal estates developed. Inns provided board and lodging for ordinary travelers, whereas the royal estates served those in royal service. Each inn and estate brewed its own beer on the premises, and it was mainly through this network that peasants learned the craft of brewing.

Brewing remained mostly artisanal until the early 1800s, with small batches brewed in the vicinity of consumption. Industrial brewing in Scandinavia didn't begin until the 1840s, when the revolutionary method of a long wort boil paired with bottom-fermenting lager yeast arrived from Germany. It introduced Finnish palates to a totally new, crystal-clear kind of beer referred to as "Bavarian" — nowadays too often replicated as "international lager."

What does that history have to do with Finnish sahti, the beverage beer writer Michael Jackson characterized as "the only primitive beer to survive in Western Europe"? One need only visit Finland today to enjoy the same libations, both in flavor and appearance, as were served in the inns of the 1500s. The beer that peasants learned to brew back then, the beer some of their descendants still make much the same way, is known as sahti.*

Sahti Today

Though a remnant of rustic brewing tradition, sahti has survived and is doing well in certain rural areas, particularly on the eastern side of Lake Päijänne, also referred to as the "sahti district." A few commercial examples are also brewed regionally, but because sahti is microbiologically alive and won't keep long once it reaches top condition (in less than two weeks), it's difficult to brew for mass consumption.

Today sahti is, at its best, a festive farm brew served at rural feasts such as summer weddings. More technically, it's a very potent, astoundingly full-bodied and turbid top-fermenting beer.

A less potent subvariety of sahti is a sweet, only partly fermented version referred to as "naisten sahti," or sahti for the womenfolk.

Sahti has a highly complex flavor spectrum that includes the fruity, banana-like notes and phenolic peaks also found in typical German Weizen. Probably the most bizarre aroma component is the juniper resins imparted by the fresh juniper twigs used in the filter bed on the bottom of the lauter tun, and often also infused in the hot brewing water hours before brewing. The other notable characteristic of sahti is that it's very turbid, for two reasons. First, proteins that would normally precipitate out as trub during an ordinary 90-minute wort boil never get that opportunity, because sahti brewers typically do not boil the wort after lautering — more on that below. These proteins are probably also the key factor behind sahti's immense fullness of body. Second, the bakers yeast used by sahti brewers is a poor flocculator that tends to stay in suspension, contributing to haze while also producing the fruity esters and phenols in sahti's aroma.

*Etymologists suggest the root of the name "sahti" might be a Swedish word, "saft," which can be translated to "juice."

Ingredients

The Grain Bill

Sahti is an all-grain, and usually all-malt, beer. The grist typically contains malted barley alone or together with some dark rye malt (5–10%), which imparts color and some rustic rye-bread flavor. Unmalted wheat is also used in some recipes, though in fairly small amounts. Finland has no Reinheitsgebot-like restrictions on ingredients, and Finnish brewers can be as liberal as their counterparts in the United States or Japan.

Unlike the sahti brewers of the 1500s, many brewers of today don't malt their barley at home, but instead buy ready-crushed malt in 20-kg (44-lb) sacks manufactured especially for this purpose. The most common brand used by sahti brewers is Lahden Aito Sahtimallas, or "The Genuine Lahti's Sahti Malt," manufactured by Lahden Polttimo Ltd. in Lahti, Finland (now called Viking Malt). It's a blend of Pilsener malt (roughly 85%), enzymatic malt (about 10%), and crystal malt (around 5%) to add color and sweet maltiness. The enzyme malt boosts the blend's enzymatic power so a reasonable degree of starch conversion can be attained at temperatures below 149 °F (65 °C), after which beta-amylase enzymes rapidly denature. Many sahti brewers use about 5–10% dark rye malt and even some unmalted wheat to complement the base malt. Two favorite grist bills are all-Pilsener malt, and a blend of Pilsener malt (80%) with Munich malt (20%).

Flavoring

Though neither hop bitterness nor aroma should be a significant part of the flavor profile of sahti, in some recipes a symbolically small amount of dried hop cones — traditionally homegrown — are scattered among the juniper twigs during the lauter. Given the small quantity and the way they're used, they hardly sway the flavor at all; the absence of a wort boil precludes adequate alpha-acid isomerization, and sahti recipes generally include no hops at all. In the flavor profile of sahti, "juniperness" replaces the hoppiness of other beer styles.

Yeast

The yeast strain used is undoubtedly the prime factor in sahti's unique flavor. Genuine Finnish sahti is fermented with commercially manufactured bakers yeast. Brewers have two distinct strains to choose from, though they're said to be manufactured under the same brand as a result of company mergers. Both are highly valued for the hefty clovelike phenolic and estery accents they produce — the hallmark of Finnish sahti. Foreign bakers yeast strains generally don't produce the desired flavor profile, which may be the trickiest obstacle for non-Finn brewers interested in making their own sahti; cultivating Finnish connections is the best way to begin cultivating a supply of sahti yeast.

Equipment

Traditional sahti brewing gear consists of an open wooden mash tun, a troughlike wooden lauter tun called a kuurna, and an upright three- or four-legged wooden fermentor fitted with a spigot for dispensing sahti at top condition straight from the fermentor. Although wooden fermentors have long since been replaced by aluminum milk cans, wooden mash tuns are still fairly common among traditional sahti families — though new ones are no longer made. Many contemporary brewers instead use woodfire-heated stainless steel kettles designed as hot water tanks for saunas and cow houses. Modern homebrewers who want to brew sahti can simply use their ordinary mashing gear; it isn't the hardware that counts.

The kuurna, probably the most extraordinary lauter tun construction in existence, is a wooden trough typically 5–8.2 ft (1.5–2.5 m) long and around 1.3–1.7 ft (0.4–0.5 m) wide and deep, with an inner cross-section that's either curved or cut into a "v." In the old days a kuurna was hollowed out of a split log — usually aspen, which is fine-grained and easy to work. Modern kuurnas are quite often made of lumber planks. Before lautering, the bottom is transversely lined with rung-like pieces of wood close enough together to form a grid, atop which a false bottom is built — traditionally of straw covered with fresh juniper twigs. One end is fitted with a bunghole at the bottom for draining the wort.

Brewing Sahti

Mashing

No matter how numerous and colorful sahti's individual family recipes and mashing practices are from a folkloristic point of view, in biotechnical terms they all compress into two techniques: scheduled (step) infusion mashing, or single-temperature (isothermal) infusion mashing.

Scheduled infusion mashing. When using a wooden mash tun, the traditional method involves two or more consecutive additions of hot water, each bumping the overall mash temperature up to the next rest. It's remarkable that although the original sahti masters knew nothing about enzymes and their optimal working temperatures, their mashing schedules result in a first rest at around 122 °F (50 °C) — corresponding neatly to a standard protein rest. The second rest at around 140–149 °F (60–65 °C) corresponds to a first saccharification rest, and a third rest at 158–167 °F (70–75 °C) can be thought of as a second saccharification rest. The wooden mash tun is usually covered during the rests to maintain warmth.

Some sahti masters still use the ancient technique of immersing furnace-heated hot stones into the mash to raise the temperature at each step instead of adding hot water — sugars caramelize on the hot stone surface, imparting a distinctive burnt-sugar flavor. Some masters use the last stone immersion to bring the mash to a boil entirely, likely because brewers long ago discovered — before Pasteur — that the brew kept better when boiled at the end of mashing. When only hot water additions are used, the mash can't be brought to a boil, though nothing forbids combining both techniques. Many brewers today use woodfire-heated kettles from their cow houses and saunas instead of wooden vessels, splitting firewood into sticks that burn off quickly to boost the mash to each desired rest, often finishing with a quick boil just as with the hot stone method.

Single-temperature (isothermal) infusion mashing. This is exactly how the Britons make their ales: malt and hot water are mixed at the start of mashing in a well-insulated mash tun, typically settling the temperature at around 149 °F (65 °C), which the insulation maintains throughout the cycle. Finnish sahti brewers using wooden mash tuns insulate their mash by covering it, traditionally with haystack.

Lautering and Sparging

Regardless of the mashing method, the finished mash is ladled into the kuurna atop the false bottom of straw and fresh juniper twigs. Brewers who lauter in a separate tun can place a bunch of fresh juniper twigs on the false bottom before pouring in the hot mash; if a combined mash/lauter tun is used, the twigs are immersed in the mash before lautering.

In traditional brewing, once the mash tun's contents have been scooped into the kuurna, the bung is opened and the sweet wort streams out. Since the first few liters are hazy, the wort is recirculated until it runs clear — a routine step in any lautering system. After the initial sweet wort is collected, the mash is sparged with hot water. The high-gravity first runnings and the lower-gravity sparged wort are often kept apart and fermented as separate batches, depending on mash thickness and the original gravity target. The low-gravity batch is sometimes served as "small beer," or occasionally continued with corn sugar for the brewer's own use, while the main batch is reserved for guests of the feast.

Brewers who don't bring their mash to a quick boil at the end of mashing commonly collect the lautered wort in a kettle and bring it to a quick boil before transferring it to the fermentor — sterilizing the wort and denaturing all enzymatic activity in the process. Other sahti masters choose not to raise the mash above 158 °F (70 °C), collecting the lautered wort straight into the fermentor to keep its amylase activity alive; that residual enzymatic activity continues breaking unfermentable dextrins into fermentable sugars throughout fermentation — the same principle whisky distillers rely on to keep their fermenting wort enzymatically active.

Fermentation

The wort cools before being pitched with bakers yeast. Although traditional fermentors were wooden, the most prevalent fermentor among contemporary sahti brewers is the 11-gallon (40-L) aluminum milk can — originally designed to guarantee hygienic, efficient milk transport from farm to dairy. Filled with hot wort and partly immersed in cold water with the lid on, the wort cools to pitching temperature in about half an hour, the same method once used to cool milk before refrigerated farm tanks became common in the late 1960s.

Sahti brewers usually set aside a small amount of wort (around 16–32 oz [0.5–1.1 L]) after lautering for a yeast starter, "awakening" two to four packs (3.5–7 oz [100–200 g]) of bakers yeast in it. As soon as the starter raises a vigorous head — normally in under 30 minutes — it's ready to pitch.

The Finnish bakers yeast used by sahti brewers is a robust top-fermenting strain that works with stunning vigor, consuming anything fermentable in hours rather than days. Pitched at a sufficient rate, it takes off within a few hours, hoisting a thick, dense layer of foam. At an ambient temperature of around 68 °F (20 °C), the fermenting wort may plummet 60 gravity points (15 °P) in less than 48 hours, and the fermentation is vigorous enough that the wort's own temperature can climb 35–38 °F (19–21 °C) above ambient.

Fermentation divides into two stages. Primary fermentation, characterized by astoundingly vigorous foam production at around 68 °F (20 °C), is finished once the foam subsides and the wort's surface re-emerges — typically within 48 hours. The fermentor is then moved to a cool locality, traditionally a ground cellar, for secondary fermentation. Since the bakers yeast slackens substantially at cellar temperature (50–54 °F [10–12 °C]), secondary fermentation usually takes about a week, during which the remaining fermentable sugars are consumed and sahti's unmistakable flavor matures. The duration and temperature of each stage, along with the pitching rate, are all freely adjustable — it's always the sahti master's job to synchronize conditioning and flavor with the brew's serving date.

One Brewer's Recipe for Sahti

Traditionally, brewing sahti is more a matter of art than technique. Old sahti masters are revered as wizards within their agrarian communities. They all have their own recipes and traditions, usually inherited from ancestors. They neither know nor care about enzymes, nor do they use thermometers or saccharometers — they depend on tradition and their own experience.

Those of us lacking that tradition have to depend on an understanding of the biotechnical and biochemical principles of brewing, combined with an imaginative approach. The following recipe is one of my favorites.

Mashing & Lautering

Make a thick mash using 10.6–13.25 gal (40–50 L) of water (2–2.5 L per 1 kg of grist, or 2.1–2.7 qt per 2.2 lb of grist). Mash in with fresh cold water. Raise the mash temperature to around 145–149 °F (63–65 °C) and let it rest until iodine-negative. Raise the mash temperature to around 158 °F (70 °C) and let it rest for 30 minutes before lautering. Immerse a bunch of fresh juniper twigs into the mash a few minutes before you begin lautering the sweet wort. If using a separate lauter tun, transfer the bunch of juniper twigs together with the mash into the lauter tun. Collect the initial sweet wort, then sparge the mash with hot water to get a total of 10.6 gal (40 L) of wort. Cool the wort and pitch with the bakers yeast.

Fermentation

Ferment for two days in a pail covered by a clean towel at an ambient temperature of around 68 °F (20 °C). After two days, siphon the fermenting wort into a canister (or canisters), leaving the sediment yeast behind. Transfer the canister(s) to cellar temperature (around 50–54 °F [10–12 °C]) for secondary fermentation for one week. The canister(s) must not be tightly closed, since fermentation is still in full swing and the CO₂ must be allowed to escape freely — sahti is always uncarbonated. As they say in Finland, when it's ready to be served, it's also treacherously ready to leave you legless.

*Be aware that some ornamental varieties of juniper may be poisonous.

Keep the Tradition Alive

Finland is too small to keep the sahti tradition alive and developing on its own — let all brewers worldwide take up the challenge.