On a restaurant’s patio or a friend’s balcony, it is time to enjoy the summer, the sun, the barbecues, with a fresh beer at hand… and no is more fresh than the pilsner.
Born in Bohemia during the 18th century, it was among the first blonde lagers. The family encompass the beers produced by bottom-fermenting. The process involves the fermentation of the mash by Sacharromyces uvarum at around 10°C in wide, shallow vats. The yeasts flocculate at the bottom of the vats, hence the name. The low temperature allows only a relatively low alcohol yield, while the short path of the CO2 bubbles produced in the vats prevents it from “fishing” out the aromatic compounds on its way up.
The resulting golden product was a huge success. Pilsners benefitted from the replacement of metal and clay mugs by clear glasses. For the first time, customers were able to see what they were drinking. Appearances in this case were not deceiving. Pilsner is defined by its crisp and fresh taste, granted by the strong aromas of hops and malt: the perfect bittersweet beer. Sadly, its flavour is as fragile as it is delectable.
Notes of skunk and cardboard can quickly deteriorate the balance of pilsners. How does this phenomenon can take place in a closed bottle? Beer is 95% water, 5-ish% ethanol, the rest being sugars and other various organic compounds creating the aroma and taste of the product. For the pilsner, many of these compounds come from the high amounts of hops added in the brewing. In recent years, it has been shown that at least 40 organic acids and furanones were responsible for the pilsner’s aroma and that a mix of 23 molecules was necessary to approximate it artificially.
Pilsner, with their high hop content are especially prone to develop a skunk odour... but only when they are stored in clear bottles. Light excites the beer’s aromatic compounds, which in turn react with specific isomers of organic acids derived from hop. Add a little sulphur compounds in the mix and the skunky 3-methylbut-2-ene-1-thiol is produced. Pilsner lovers learn quickly to beware of clear bottles and to go for cask or cans.
But the lager’s skunk odour is not the only danger for the pilsner it is also prone to develop during storage a strange “off’ taste. Recently, it has been shown that a class of compound, a-dicarbonyls, are steadily produced by the enolization of carbohydrates. There was no surprise there: Sacharromyces is one of the most creative chemist and new compounds are discovered everyday in alcohols.
Born in Bohemia during the 18th century, it was among the first blonde lagers. The family encompass the beers produced by bottom-fermenting. The process involves the fermentation of the mash by Sacharromyces uvarum at around 10°C in wide, shallow vats. The yeasts flocculate at the bottom of the vats, hence the name. The low temperature allows only a relatively low alcohol yield, while the short path of the CO2 bubbles produced in the vats prevents it from “fishing” out the aromatic compounds on its way up.The resulting golden product was a huge success. Pilsners benefitted from the replacement of metal and clay mugs by clear glasses. For the first time, customers were able to see what they were drinking. Appearances in this case were not deceiving. Pilsner is defined by its crisp and fresh taste, granted by the strong aromas of hops and malt: the perfect bittersweet beer. Sadly, its flavour is as fragile as it is delectable.
Notes of skunk and cardboard can quickly deteriorate the balance of pilsners. How does this phenomenon can take place in a closed bottle? Beer is 95% water, 5-ish% ethanol, the rest being sugars and other various organic compounds creating the aroma and taste of the product. For the pilsner, many of these compounds come from the high amounts of hops added in the brewing. In recent years, it has been shown that at least 40 organic acids and furanones were responsible for the pilsner’s aroma and that a mix of 23 molecules was necessary to approximate it artificially.
Pilsner, with their high hop content are especially prone to develop a skunk odour... but only when they are stored in clear bottles. Light excites the beer’s aromatic compounds, which in turn react with specific isomers of organic acids derived from hop. Add a little sulphur compounds in the mix and the skunky 3-methylbut-2-ene-1-thiol is produced. Pilsner lovers learn quickly to beware of clear bottles and to go for cask or cans.But the lager’s skunk odour is not the only danger for the pilsner it is also prone to develop during storage a strange “off’ taste. Recently, it has been shown that a class of compound, a-dicarbonyls, are steadily produced by the enolization of carbohydrates. There was no surprise there: Sacharromyces is one of the most creative chemist and new compounds are discovered everyday in alcohols.
The real interest came with the realization that the a-dicarbonyls were degraded in aldehydes and enols in a Maillard reaction. These reactions take place usually at high temperatures between a reducing sugar and an amino acid or a peptide, producing tasty, brownish products. We have to thank it for the bread’s crust, caramel and roasted coffee. In a Pilsner bottle though, the Maillard reaction to happen (although quite slowly), and produces... the unwanted flavours of expired beer. The next step for the industry would now consist of inhibiting the final step. Sulphites, by examples have this ability, albeit they are not popular among the public, without real ground... But that would be the subject of another column...
For further reading :
Bravo et al. J. Agric. Food Chem. (2008) 56(11), 4134-44
Fritsch et al. J. Agric. Food Chem. (2005) 53(19), 7544-51
Jaskula et al. J. Agric. Food Chem. (2008) 56(15), 6408-15
For further reading :
Bravo et al. J. Agric. Food Chem. (2008) 56(11), 4134-44
Fritsch et al. J. Agric. Food Chem. (2005) 53(19), 7544-51
Jaskula et al. J. Agric. Food Chem. (2008) 56(15), 6408-15
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