by Ilkka Sysilä (Brewing Techniques)
Though modern brewers have taken some liberties with modern brewing materials, this anachronistic style is still being brewed by sahti masters as it was 400 years ago: in wooden vessels with a filter bed made of juniper twigs. As they say in Finland, “Kippis!”
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: in 1504 the castellan of Stockholm’s royal castle of Sweden preferred to procure all the beer he could from Finland). At that time, Finland was an eastern province of the Kingdom of Sweden. It served 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, depending on the cargo, was around 19–25 miles (30–40 kilometers), 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. The royal estates served as administrative centers and model farms for the peasantry in the region; it was mainly through this network that peasants learned the craft of brewing beer.
Brewing remained mostly artisanal until the early 1800s. Batches were quite small and were brewed in the vicinity of consumption. Industrial brewing in Scandinavia didn’t begin until the 1840s when the revolutionary brewing method of using a long wort boil and bottom-fermenting yeast (lager yeast) arrived from Germany. It introduced Finnish palates to a totally new kind of beer of crystal-clarity referred to as “Bavarian,” nowadays too often replicated as “international lager.”
What does the foregoing have to do with Finnish sahti, the beverage characterized by beer writer Michael Jackson 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 in the 1500s, the beer some of their descendants still make much the same way it was made back then, is known as sahti.*
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 Paijanne, also referred to as the “sahti district.” A few commercial examples are also brewed regionally, but because sahti is microbiologically alive and will not keep long once it reaches its top condition (in less than two weeks), it is difficult to brew for mass consumption.
*Etymologists suggest the root of the name “sahti” might be a Swedish word “saft,” which can be translated to “juice.”
Today sahti is, at its best, a festive farm brew served at rural feasts such as summer weddings. More technically, sahti is a very potent, astoundingly full-bodied and turbid top-fermenting beer. The original gravity of sahti ought to be no less than 1.075 (18 °P). In fact, a more typical sahti brewed for festive purposes varies in range from 1.100 to 1.120 (25–30 °P). Its alcohol content typically varies from 7 to 11% (v/v), though 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, bananalike notes and phenolic peaks also found in typical German Weizen. Probably the most bizarre aroma component in sahti 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 (or decocted) in the hot brewing water hours before brewing (techniques vary depending on the desired strength of the juniper flavor). The other notable characteristic of sahti is that it is very turbid, for two reasons. First, proteins that would normally precipitate out in the form of trub during an ordinary 90-minute wort boil never get that opportunity with sahti because brewers of this style do not typically boil the wort after lautering. (Yes, you heard correctly; more on other ramifications of not boiling later.) These proteins are probably also the key factor behind the immense fullness of body characteristic of sahti. Furthermore, the bakers yeast used by sahti brewers is a poor flocculator that tends to stay in suspension and also contributes to haze. This yeast strain is also responsible for the fruity esters and phenols in sahti’s aroma.
The grain bill: Sahti is an all-grain (and usually all-malt) beet. The grist of sahti mash typically contains malted barley alone or together with some dark rye malt (5–10%). Dark rye malt 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 do not 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. Lahden Aito Sahtimallas is a blend of Pilsener malt (probably around 85%), enzymatic malt (about 10%), and crystal malt (around 5%) to add color and sweet maltiness. The enzyme malt boosts the enzymatic power of the blend so that a reasonable degree of conversion of starch into sugars can be attained at temperatures below 149 °F (65 °C), after which beta-amylase enzymes rapidly become denatured (they are totally denatured at 158 °F [70 °C]). Many sahti brewers use about 5–10% dark rye malt and even some unmalted wheat to complement the Lahden Aito Sahtimallas base malt. My two favorite sahti malt bills are all-Pilsener malt grist and a blend of Pilsener malt (80%) and Munich malt (20%). (As mentioned earlier, sahti brewers are free to improvise.)
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. Considering the small quantity of hops and the way they are used, they hardly have any sway at all over the flavor of sahti. (Hops used to be more common in sahti brewing, but probably only as a source of aroma. The absence of a wort boil precludes adequate alpha-acid isomerization.) It ought to be emphasized that sahti recipes generally do not include hops at all. In the flavor profile of sahti, “juniperness” replaces the hoppiness of other beer styles.
Yeast: The yeast strain used by sahti brewers is undoubtedly the prime factor in sahti’s unique flavor. Today, genuine Finnish sahti is fermented with commercially manufactured bakers yeast. Brewers have two distinct yeast strains from which to choose, though they are said to be manufactured under the same brand as a result of company mergers. Both strains (if there really are two coexisting strains under the same brand) are highly valued for the hefty clovelike phenolic and estery accents they produce, the hallmark of Finnish sahti. I have experimented with some foreign bakers yeast strains and they did not produce the desired flavor profile. This may be the trickiest obstacle for non-Finn brewers interested in making their own sahti. My only advice is to begin cultivating Finnish connections, then perhaps begin cultivating your own supply of sahti yeast.
Traditional sahti brewing gear consists of an open wooden mash tun, a troughlike wooden lauter tun (called a kuurno), and an upright three- or four-legged wooden fermentor fitted with a spigot for dispensing and serving the ready-fermented sahti at top condition straight from the fermentor. Although these wooden fermentors have long ago been replaced by aluminum milk cans, wooden mash tuns are still quite common among traditional sahti families. Unfortunately, new ones are no longer made. Many contemporary sahti brewers use woodfire-heated stainless steel kettles designed to be used as hot water tanks in saunas and cow houses instead of the traditional wooden mash tun. Obviously, modern home brewers who wish to brew sahti can use their ordinary mashing gear; it’s not the hardware that counts (much).
The kuurna, or lauter tun: The kuurna, probably the most extraordinary lauter tun construction in existence, is a wooden trough, typically 5–8.2 ft (1.5–2.5 meters) long and around 1.3–1.7 ft (0.4-0.5 meters) wide and deep. The cross-section of the kuurna’s inner surface is either curved (semicircular) or cutconical (with side walls inwardly slanting towards the straight striplike bottom, forming the shape of a “v”). In the good old days kuurnas were hollowed out into a split log of a tree, usually aspen, which is fine-grained and easy to work with. The wooden kuurnas of today are quite often made of lumber planks. Before lautering, the bottom of the kuurna is transversely lined with runglike straight pieces of wood (see photo, above), close enough to one another to make a grid atop of which a false bottom is built — traditionally of straws covered with fresh juniper twigs. One end of the kuurna is fitted with a bunghole at the bottom for draining the wort.
Mashing: No matter how numerous and colorful sahti’s individual family-associated recipes and mashing practices are from the folkloristic point of view, in biotechnical terms they can all be compressed into two techniques: either scheduled (step) infusion mashing or single-temperature infusion mashing (isothermal mashing).
Scheduled infusion mashing. When using a wooden mash tun, the traditional sahti mashing method involves two or more consecutive additions of hot water into the mash tun. Each addition of hot water bumps the overall mash temperature up to the next step, of rest. It is quite amazing to see 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). This corresponds quite neatly to the standard protein rest. The second rest at around 140–149 °F (60–65 °C) corresponds to what we may call the first saccharification rest. Quite often a third rest is taken at around 158–167 °F (70–75 °C), which can be referred to as the second saccharification rest. The wooden mash tun is usually covered during the rests to maintain its warmth.
Some sahti masters still use the ancient technique of immersing furnace-heated hot stones into the wooden mash tun to raise the temperature for each step instead of adding hot water. Sugars caramelize on the hot surface of the stones, imparting a distinctive, burnt sugar flavor to the brew. I know of at least one sahti master who uses the hot stone method exclusively.
Some sahti masters use the last immersion of hot stones (usually the fourth one) to bring the mash in the wooden mash tun to a boil. The impetus for bringing the mash to a quick boil at the end of mashing presumably originates from the discovery (made long before Pasteur) that the brew kept better when boiled at the end of mashing.
When only the additions of hot water are used, the mash cannot be brought to a boil. Nobody has ever been forbidden, however, from combining the two thermodynamic expedients.
As said earlier, many Finnish sahti brewers of today use woodfire-heated kettles from their cow houses and saunas as mash tuns instead of the original wooden vessels (these hot water kettles can be found in almost every Finnish cow house or country sauna). For scheduled infusion mashing, the firewood burned in the furnace of the kettle is often split into sticks. Sticks burn off quickly and release the desired amount of heat to boost the mash temperature to the desired rest. As with the hot stone technique, the brewer starts with a cold mash and then adds heat to reach each step. The last stoking of the furnace is quite often used to bring the mash to a quick boil at the end of mashing, just as it is done with hot stones.
Single temperature (isothermal) infusion mashing. Isothermal infusion mashing means infusion mashing at a single temperature. This is exactly how the Britons make their ales: Malt and hot water are mixed at the beginning of the mashing process in a well-insulated mash tun. The mixing is done so that the temperature of the mash settles usually at around 149 °F (65 °C). Mash tun insulation maintains the mash at this temperature throughout the cycle. Finnish sahti brewers using wooden mash tuns insulate their mash by covering them, traditionally with haystack.
Lautering and sparging: Regardless of the mashing method used by the sahti brewer, the finished mash is ladled into the kuurna atop the false bottom of straws and fresh juniper twigs. Modern home brewers can duplicate this procedure quite easily, whether they use a separate, dedicated vessel or a combined mash/lauter tun. Brewers who lauter in a separate tun can place a bunch of fresh juniper twigs (about the size of a proper bouquet of flowers) on the false bottom before pouring in the hot mash. If a combined mash/lauter tun is used, the juniper twigs should be immersed in the mash before lautering.
In traditional brewing, once the contents of the mash tun have been scooped into the kuurna, the bung at the other end of the kuurna is opened and the sweet wort streams out. Since the first few liters are quite hazy, the wort is recirculated until it runs clear and free of solid particles — a routine procedure in any brewery using a conventional lautering system. After the initial sweet wort has been collected, the mash in the kuurna is sparged with hot water. The sweet high-gravity first runnings and the lower-gravity sparged wort are often kept apart and fermented as separate batches. Whether this separation is done depends on the thickness of the mash and the original gravity requirements of the wort. The low-gravity batch would be served as “small beer” or (I hate to make a revelation like this!) quite often “continued” with corn sugar and then fermented for the use of the brewer (the main batch is naturally reserved for guests of the feast).
A quite common practice among those sahti brewers who do not bring their mash to a quick boil at the end of the mashing in the way(s) described earlier is to collect the lautered wort in their kettle and bring the wort to a quick boil before transferring it into the fermentor. This practice not only sterilizes the wort, but it also denatures all enzymatic activity.
On the other hand, many sahti masters choose not to raise the mash temperature over 158 °F (70 °C) and collect the lautered wort straight into the fermentor to keep its amylase activity alive. This residual enzymatic activity breaks unfermentable dextrins into fermentable sugars throughout fermentation. This is also how whisky distillers keep their fermenting wort enzymatically active, for quite obvious reasons!
Fermentation: The wort in the fermentor then cools before it is pitched with bakers yeast. As stated earlier, although traditional fermentors were wooden, the most prevalent fermentors used by contemporary sahti brewers are 11-gallon (40-L) aluminum milk cans. These cans were originally designed to guarantee the hygiene and efficiency of milk transportation from the countryside to the dairies. When the aluminum can is filled with hot wort and partly immersed into cold water with the lid on, the wort cools down hygienically to yeast pitching temperature in half an hour. This practice was used to cool down the milk immediately after milking before refrigerated farm tanks became common in the late 1960s. Again, the choice of type of fermentor and cooling method is up to you.
Sahti brewers usually set aside a small amount of wort (around 16–32 oz [0.5–1.1 L]) after lautering for the yeast starter. Two to four packs (3.5–7 oz [100–200 g]) of bakers yeast is then “awakened” in the starter wort. As soon as the starter yeast raises a vigorous head (normally this takes less than 30 minutes), it is ready to be pitched into the cooled wort.
The Finnish bakers yeast used by sahti brewers is a robust top-fermenting strain, a real knave of the yeast world! It works with stunning vigor, consuming anything fermentable in hours rather than days. Pitched at a sufficient rate this ruffian yeast takes off within a few hours’ time, hoisting a very thick and 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! The fermentation is so vigorous that the temperature of the fermenting wort may rise up to 35–38 °F (19–21°C) above the ambient temperature.
The fermentation of sahti can be technically divided into primary and secondary stages. The primary fermentation is characterized by astoundingly vigorous foam production. The ambient temperature of the primary fermentation is usually around 68 °F (20 °C). It is finished once the foam has subsided and the surface of the fermenting wort begins to emerge again. This means that the primary fermentation is over within 48 hours from the rise of the foam. The fermentor is then transferred to a cool locality for secondary fermentation, traditionally a ground cellar. Since the bakers yeast is a top-fermenting strain and its metabolism slackens substantially at cellar temperature (50–54 °F [10–12 °C]), the secondary fermentation usually takes one week. During the secondary fermentation, the remaining fermentable sugars are consumed by the yeast and the exquisite, unmistakable sahti flavor matures.
The variables of fermentation, such as the duration and the temperature of the primary fermentation versus the secondary fermentation, as well as the yeast pitching rate, are freely adjustable to meet individual needs. It is always the sahti master’s responsibility to synchronize the conditioning and flavor of the brew to correspond with its serving date.
Finland is too small to keep the sahti tradition alive and developing; let all brewers worldwide take up the challenge.
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