Lots of things go well with beer: pizza, nuts, chips . . . .

But watch out for those alpha-dicarbonyls.

These chemicals are carbohydrate derivatives in beer past its prime, according to Venezuelan scientists. And neutralizing them could keep beer fresh longer.

The alpha-dicarbonyls don't taste bad, but they can degrade or react with other compounds to create undesirable flavors, the scientists reported in the current Journal of Agricultural and Food Chemistry.

These include cardboard, caramel and rose scents. That combination upsets the flavor balance, says lead author Adriana Bravo, a chemist at Caracas-based food and beverage giant Empresas Polar.

"The fresh flavor of a beer is a very delicate equilibrium," she says.

When the scientists added yet another chemical to block alpha-dicarbonyl reactions, they reduced the creation of unwanted odors.

That added chemical is toxic, so it could not be used in the actual beer-making process. But the work helps researchers understand the aging process so they can look for other ways to stop it, she says.

Tim Wadkins, quality assurance director at Victory Brewing Co. in Downingtown, said the industry has previously tried to combat staleness by reducing oxygen levels while brewing and bottling.

But this approach has been only partly successful. So the new findings may lead to better options, he says.

You may someday credit science for giving beer a longer shelf life. Then again, you could just drink it more quickly.

- Tom Avril