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Bitter Beer Banished By Better Chemistry?

April 14, 2011

Stale bottled beer may soon not be a problem any longer as scientists have identified the chemical reactions that lead to the bitterness of old beer.

Chemicals present in the ingredient hops will break down over time, forming other compounds that result in the unpleasantness, BBC News reports.

Avoiding that breakdown of the hops is the secret to keeping beer fresher for a longer time, researchers report in the Journal of Agricultural and Food Chemistry, by keeping the beer cool during storage and shipping and adjusting the pH balance during manufacturing.

Unlike wine, scotch whiskey, and bourbon, beer tastes best when consumed fresh. Experts estimate that the average beer, depending on the variety, goes bad after 6 to 12 months of storage.

That naturally-present, slightly bitter-tasting compounds being the source of the more bitter and long-lasting flavors of “aged” beer is not a new realization in brewing. However knowing the exact compounds that are responsible and how they react over time has remained elusive until recently.

Researchers at the Technical University of Munich (TUM) have been diligently investigating the particulars of beer chemistry for a number of years. Recently they stored a number of commercially available, pilsner-style beers for as long as 10 years in order to compare the chemistry of aged ales with that of recently brewed examples.

Studies show that the level of pH has a strong effect on the degradation of trans-iso-alpha acids, but the new study indicated that pH in ageing beer was incredibly stable. Researchers asked a commercial brewer to make batches of beer with varying pH levels.

As the brewing became incrementally less acidic, the trans-iso-alpha acid degradation process could be much reduced. It was found, however, that the reactions involved in making stale-tasting beer are accelerated at higher temperatures, so keeping beer cool had the best results in keeping beer fresh.

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