London: Researchers claim to have for the first time discovered a way for extending the life of beer so that it stays fresh and tastes good for long, after they identified the substances which contribute to the beverage's bitter taste as it ages.

Beer can develop an unpleasant, bitter aftertaste as it ages. Unlike wine, scotch whiskey, and bourbon, beer tastes best when consumed fresh. Experts estimate that the average beer starts to taste bitter after 6 to 12 months of storage.

Past studies have identified dozens of bitter-tasting substances formed during beer manufacturing -- the ‘prenylated polyketides’ derived from hops. But, until now, there was no solid information about the bitter substances in aged beer.

Now, a team, led by Thomas Hofmann at the Technical University of Munich, has identified the main substances that cause the bitter aftertaste of aged beer, and also suggests ways to prevent the formation of the substances that could help extend its freshness.

The researchers, in fact, have identified some 56 substances that contribute to beer's bitter taste, including five which appear to be largely responsible for its harsh flavour after ageing.

They have based their findings on an analysis of a variety of commercial beers both before and after storage.

The findings have been published in the latest edition of the 'Journal of Agricultural and Food Chemistry'.