The lager type beer was so well-preserved that researchers were able to describe its original characteristics using chemical analyses.
They also tasted the beers and said they ranged from intensely sulfuric to sour, and had flavors that ranged from fecal to fruity.
The three lager beers apparently were produced during the World War I era and stored in a large cold cellar at the brewery, where they were gathering dust.
The beer, which was bottled in dark glass and well sealed, was discovered during the reconstruction of a brewery in Záhlinice, Czech Republic.
The researchers, based at the Research Institute for Brewing and Malting in Prague, Czech republic, decided to analyze the beer for insights into early 20th century brewing processes, as well as the chemical changes that occur in beer over long periods of time.
To analyze the beers, the researchers began by tasting it.
In their study, they wrote: ‘Because of the small volume of the century-old beer samples, sensory analysis was carried out by only five members of our sensory panel.
‘A descriptive analysis of flavor and taste was performed immediately after opening of the bottles’.
Following this, they conducted a chemical analysis to identify properties such as the original extract, alcohol content, color and total acidity.
They used a method called high performance liquid chromatography as well as other techniques to compare the beers’ features to those of modern day brews.
The old beers had higher alcohol content and were less bitter than the beers of today.
They also contained more iron, copper, manganese and zinc.
The researchers also conducted a DNA analysis of the beer to identify any microorganisms present.
The first beer was ‘sensorially the least acceptable,’ according to the researchers.
‘It was light, hazy with very intensive sulphuric and fecal off-flavor,’ they wrote.
Although no yeast DNA was detected, the DNA of bacteria Staphylococcus and Streptomyces was found.
The second beer, the researchers said, resembled lambic – a beer brewed in the Pajottenland region of Belgium.
‘It was dark, very sour with madeira and nicely fruity off-flavors,’ they wrote.
No bacterial DNA was identified but several types of yeas were.
The third beer was light brown and contained traces of carbon dioxide bubbles.
‘While the beer was oxidized, with typical sweetness and papery off-flavors, it was very slightly bitter and it really appeared as beer,’ the researchers wrote.
This beer contained the DNA of yeast and bacteria and was the only one that tasted like beer of today.
The researchers said that the chemical changes in the first two beers were caused mainly by microbial contamination, whereas the third beer remained largely uncontaminated.
‘The beer C (third beer) enabled us to acquire deeper knowledge about a 100-year-old beer which, due to undamaged sealing cork plug and most probably constant temperature in the cellar, underwent a “natural” aging process unmarred by microbial contamination, which resulted in an unspoiled sensory profile’.
The researchers concluded their study writing ‘One can assume that a century ago our ancestors produced beer from similar raw materials and in a similar way as today’.