by Brian Gibson
Archaeological brewing at VTT
The work of an archaeologist is complicated by the fact that the materials under investigation are invariably imperfect. Metal artefacts rust, wood decomposes, DNA degrades, bones and clay vessels shatter. Time leaves only a suggestion of the original materials’ properties and the archaeologist is left to conclude as much as possible from the limited information available. However difficult, with the right approach one can learn much from ancient materials regardless of the size or condition. In this post I write about two of our recent archeological brewing projects: shipwreck beer and sahti.
How to interpret information from compromised samples was an issue faced by a team at VTT after receiving two bottles from the ‘Champagne wreck’ – the remains of a schooner found on the sea bed near the Åland Islands in the Baltic sea. Archaeological analysis dated the wreck to sometime in the 1840s. The bottles appeared to contain beer but sensory analysis was impossible due to extensive bacterial spoilage of the beer. Trained beer tasters described the contents in less than favourable terms: rancid, goaty, sulphuric. With such degraded samples it was difficult to imagine how the beer would have originally tasted or how it could be recreated.
The first challenge of the VTT team, led by Dr John Londesborough, was to determine if the contents were, in fact, beer. This was done through sugar analysis which revealed traces of maltose and maltotriose, which are the main sugars present in beer. Further confirmation came from collaboration with partners at the University of Munich who showed unequivocally that the samples contained hops, one of the main ingredients of beer and one which is not found in other beverages. Having established that the samples were beer, it was necessary to determine the level of sample degradation. In particular, it was crucial to determine the level of seawater contamination. The bottles recovered were sealed with corks, which offered only limited protection against the entry of seawater. By determining the concentration of sodium in the beer it was possible to calculate the level of NaCl (salt) and therefore seawater contamination, which in both bottles was approx. 30%.
Analysis in Munich showed that the hop components were extensively degraded, but the concentrations and kinds of degradation compounds could be used to determine what the original compounds were. The presence of hop iso-α-acids indicated that the wort had been boiled prior to fermentation. A relatively high level of β-acids showed that the hops were less refined than today’s varieties (β-acids have been bred out of modern hop varieties because of their harsh taste). The ethanol concentration (correcting for seawater-contamination) was a relatively mild 4.5% alcohol by volume (ABV). The fruit and floral flavours characteristic of beer were in the normal range, except that the concentrations of 2-phenylethanol were relatively high. This would have imparted a touch of rose aroma to the beers. The presence of a volatile phenol giving a slight clove aroma was also detected. This suggests that the beer may have been ale, as such flavours are not produced by lager yeast.
Detailed microbiological analysis failed to recover any viable yeast cells from the beer, though microscopy revealed abundant dead cells. Likewise, any yeast DNA that may have been present originally was absent – probably degraded enzymatically by the bacteria that appear to have been much more tolerant of the conditions in the bottles during their long storage.
Despite the many challenges faced by the VTT team that analysed the bottles, recreation of the beer, based on the physical and chemical profiling carried out at VTT (and some creative licence) was possible, and Stallhagen’s 1843 beer can now be purchased in Finnish supermarkets. More detailed results of the study can be found in the Journal of Agriculture and Food Chemistry:
Londesborough, J., Dresel, M., Gibson, B., Holopainen, U., Mikkelson, A., Seppänen-Laakso, T., Viljanen, K., Virtanen, H., Wilpola, A., Kivilompolo, M., Hoffmann, T. & Wilhelmson, A. (2015) Analysis of beers from an 1840s’ shipwreck. Journal of Agriculture and Food Chemistry, DOI: 10.1021/jf5052943.
Sahti: a part of Finland’s living heritage
In 1938, fishermen off the coast of South Africa hauled up an unusual fish. This find was exceptional not because the fish was unknown to science but rather because the species was known only from the fossil record. It had been believed that this fish, the coelacanth Latimeria chalumnae had become extinct 65 million years previously. The coelacanth is one of a number of species that seem to have resisted the effects of evolution over a huge stretch of time. The gingko tree is another notable example which has survived, essentially in the same form, for 170 million years. Darwin, in the Origin of Species wrote:
“…these anomalous forms may almost be called living fossils; they have endured to the present day, from having inhabited a confined area, and from having thus been exposed to less severe competition.”
Such species are uniquely valuable as they provide a direct link to the past. One does not need to base conclusions on scraps of information from long dead and degraded material but can study the real thing in detail. Such studies provide not just a glimpse into the past but also a clearer understanding of how evolutionary forces have shaped modern species; relatives of the lobe-finned coelacanth eventually became the first land animals. The concept of the living fossil is not necessarily restricted to biological species but can also be applied to the cultural sphere; many traditions, customs, languages, celebrations, etc. have survived unchanged over long periods and offer a unique glimpse into the past. One can even apply this concept to brewing of beer. One relevant example is Finland’s own sahti beer, which appears to have been brewed in more or less the same way for hundreds of years.
Sahti is one of the few ‘ancient’ beer styles still produced in Europe and differs in many respects to modern beers. The main difference is that hops are not an essential ingredient in sahti. Hops have been used to add bitterness and aroma to beer since around 800 AD. Prior to this, a diverse range of ingredients were utilized to add bitterness and balance to beer flavour. These included anise, heather, cinnamon, clove, coriander, liquorice and, as in the case of sahti, juniper. Sahti’s method of production pre-dates the use of hops and is often described as an ancient beer style for exactly this reason. In the EU, sahti is protected by ‘Traditional Speciality Guaranteed’ label, implying that commercial use of the name is restricted to beer produced according to the traditional, registered production method. But what exactly is sahti and how does it differ from modern beers? These questions motivated scientists at VTT to carry out the first comprehensive physical and chemical study of sahti beer.
By analysing samples collected throughout the traditional sahti brewing region of southern and south-western Finland, the researchers showed that, in every respect, sahti was different to commercially available lager, wheat and porter beers. All 12 sahti beers were strong with average alcohol levels of 8% ABV but also with high levels of residual sugars, in some cases more than 100g per litre. Sahti is typically brewed with baker’s yeast rather than brewer’s yeast and this imparts specific flavour characteristics to the beer. In particular, sahti beers contain a trace of clove aroma, which is normally only found in wheat beers. Like English ales, sahti beers have little or no foam – in this case probably because of the high sugar concentration and the absence of wort boiling, both of which are expected to limit foam stability. Other unique features of sahti are a very low level of bitterness due to the absence of hops and an intense fruit flavour due to esters produced by the yeast during fermentation. In some cases the concentrations of fruit compounds were more than ten times higher than in commercial beers. These compounds give sahti its intense banana aroma for example.
As sahti wort is not boiled and contains little or no hops (a natural antimicrobial agent), sahti beer tends to stay fresh for only a short period. The ephemeral nature of the product has probably contributed to its limited geographic distribution and this may, as Darwin contended for biological species, explain why this beer has not ‘evolved’ in the same way as other European beer styles.
Our study has emphasised the uniqueness of sahti beer compared to modern beers and has introduced the international brewing research community to a very individual style of beer and an important part of Finland’s living heritage. Results appear in an upcoming issue of the Journal of the Institute of Brewing:
Jukka Ekberg, Brian Gibson, Jussi Joensuu, Kristoffer Krogerus, Frederico Magalhães, Atte Mikkelson, Tuulikki Seppänen-Laakso & Arvi Wilpola (2015) Physicochemical characterization of sahti, an ‘ancient’ beer style indigenous to Finland. J Inst Brew. In press.
Dr. Brian Gibson has worked at VTT Technical Research Centre of Finland, Ltd. as Senior Scientist and Project Manager since 2009. Brian is responsible mainly for projects relating to brewing yeast biology, fermentation efficiency and beer quality. Current topics of interest include improvement of yeast performance through hybridization and/or adaptive evolution as well as optimization of process conditions. The underlying mechanisms (genetic, molecular, physiological) that govern yeast performance are a main topic of interest. firstname.lastname@example.org