Modern analyses of ancient beer

A recent issue of the Journal of Agriculture and Food Chemistry published an interesting article on chemicals in beers from an 1840s’ shipwreck. 

(photo source: http://www.sci-news.com/, Image credit: John Londesborough et al.) 

In 2010, underwater archaeologists discovered an old schooner south of the Åland Islands at a depth of 50 m in the Baltic Sea. Archeological evidence suggests the shipwreck occurred during the 1840s, but the schooner’s name, its destination and its last port-of-call were not identified. Archeologist brought the cargo consisting of luxury items, including more than 150 bottles of champagne and five bottles that look like typical early 19th century beer bottles to the surface. One of these cracked in the divers’ boat. The liquid that foamed from the cracked bottle looked and, according to the divers, tasted like beer.

Researchers from Finland analyzed two bottles of the beer from the shipwreck  and six bottles of modern  beers (Leffe Brune, Koff Porter, Weihenstephan Hefe Weissbier, Paulaner Hefe Weissbier, Aldaris Porteris Alus, and Olvi Sandels) as reference. The founding provides clues for beer makers to resurrect the flavors of ages past.

The beer samples were degassed by ultrasonification and filtered (0.45 μm). An aliquot (5 μL) was loaded to an HPLC-MS/MS system (high performance liquid chromatography coupled with tandem mass spectrometry) and analyzed for hops related compounds (native or degradation products).

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Sidenote (from Wikipedia): Hops are the female flowers of the hop plant, Humulus lupulus.

Hops are used primarily as a flavoring and stability agent in beer. Hops impart a bitter, tangy flavor to beer. Hops have antibacterial effect that favors the activity of brewer's yeast over less desirable microorganisms and for many purported benefits such as balancing the sweetness of the malt with bitterness and contributing a variety of desirable flavors
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Above: Chemical structures of bitter chemicals identified in hops and freshly brewed beer; Below: Chemical structures of bitter chemicals identified in aged beer (Source: J. Agric. Food Chem. 2010, 58, 7930–7939)
Based on the chemical fingerprint in the beer, the two bottles of ancient beer were identified as two different kind of beer.  One was more strongly hopped than the other. 

High levels of organic acids, carbonyl compounds, and glucose indicated extensive bacterial and enzyme activity during aging. However, concentrations of yeast-derived flavor compounds were similar to those of modern beers, except that 3-methylbutyl acetate

was unusually low in both beers and 2-phenylethanol

and possibly 2-phenylethyl acetate

were unusually high in one beer. Concentrations of phenolic compounds were similar to those in modern lagers and ales

Besides hops related chemicals, the researchers also analyzed other chemical components in the ancient beer. Compared to typical modern lagers and ales, ethanol contents of the shipwreck beers were low (2.8-3.2%). Glycerol and ethanol had a ratio of 4.5% for both shipwreck beers, which is typical for a yeast fermentation product. Both beers were acidic, but their pH were ~1 below modern values. The color strengths were in the range of modern ales and lagers, and much lower than porters or stouts. Possibly been oxidized after over the 170 years, sulfur dioxide was not detected in shipwreck beers. Protein levels were very low in both beers.

References: 

• John Londesborough, Michael Dresel, Brian Gibson, Riikka Juvonen, Ulla Holopainen, Atte Mikkelson, Tuulikki Seppänen-Laakso, Kaarina Viljanen, Hannele Virtanen, Arvi Wilpola, Thomas Hofmann, and Annika Wilhelmson J. Agric. Food Chem. 2015, 63, 2525−2536 DOI: 10.1021/jf5052943 Analysis of Beers from an 1840s’ Shipwreck 2015, 63 (9), pp 2525–2536
• Gesa Haseleu, Annika Lagemann, Andreas Stephan, Daniel Intelmann, Andreas Dunkel and Thomas Hofmann. Quantitative Sensomics Profiling of Hop-Derived Bitter Compounds Throughout a Full-Scale Beer Manufacturing Process. J. Agric. Food Chem., 2010, 58 (13), pp 7930–7939 DOI: 10.1021/jf101326v
• http://www.sci-news.com/othersciences/chemistry/science-beer-1840s-shipwreck-finland-02567.html