The science behind beer nuts

WHY DO bars serve nuts?

I'd always assumed it was to make you thirsty so you'd drink more beer. But that's only half right, as the taste and smell experts from University City's Monell Chemical Senses Center proved to me on a recent afternoon of sudsy experimentation.

The center's researchers were gearing up for the Philadelphia Science Festival, the citywide nerd expo that runs through Sunday. Beer drinkers in particular will want to dip into Monell's fun presentation tomorrow at Yards Brewery, where they'll explain the chemistry behind beer-and-food pairings.

Beer and peanuts, of course, is the classic pairing. But according to Marcia Pelchat, a Monell associate member who specializes in the mechanics of food cravings, that's not because nuts make you thirsty.

Instead, Pelchat said, peanuts make beer easier to swallow.

First, remember that beer is not soda or juice - it's an adult beverage with complex, often-challenging flavors.

One of those flavors is bitterness, a product of the hops that are added to balance the sweetness of your beer's malt.

Human beings detect bitterness as an unpleasant sensation, a genetic protection against swallowing dangerous toxins.

For reasons that aren't completely clear, Pelchat said, the taste of bitterness is countered by sodium chloride - good, ol' table salt. Somehow salt blocks the molecules that create bitterness.

Don't believe me? Next time you're picking at the salad bar, grab a hunk of raw radicchio, that red-streaked leafy stuff you thought was there only for decorative purposes. It's crazy bitter - unless you salt it. Then it tastes spicy, like pepper.

But it takes more than just the salt for beer to go down easy, for there's another ingredient that challenges the mouth: tannic acid.

Tannins are a by-product of the brewing process, but they have no real flavor. Rather, tannic acid creates the sensation of astringency by binding the lubricating proteins in saliva and drying the surface of the mouth. That astringency enhances other flavors in beer.

And what counteracts astringency? Fat. It relubricates the mouth.

Give it a try: Grab a Flemish red ale such as Rodenbach or Duchesse de Bourgogne. Neither are particularly bitter, but they are quite astringent, thanks to tannic acid. You can't help but pucker up.

Take a bite of cheese. The astringency disappears and the beer flows past the tonsils with ease.

These experiments may not work for you, but don't blame it on your sense of flavor. Blame it on your nose.

Our sense of aroma is 10,000 times greater than our sense of taste, Pelchat said, and our sensitivity to certain aromas varies.

For example, I'm particularly sensitive to diacetyl, another by-product of the brewing process. It smells like the fake butter in microwave popcorn, and it's especially noticeable in British pale ales. Others may not notice it at all.

Now, we could sit around all night, munching radicchio and analyzing flavor and aroma, but this is America, darn it.

When we belly up to the bar, we are not reaching for Wheat Thins spread with Brie. When we sling back, it's with a mug of brew in one hand and a fistful of fat and salt in the other.

Ah, nuts!

The Philadelphia Science Festival presents Beer Chemistry at 7 p.m. tomorrow at Yards Brewery (901 N. Delaware Ave.). The event features Yards' master brewers and Monell's scientists in an exploration of the science behind beer flavors, and - in Pelchat's words - "What makes pork belly taste so good with Tavern Spruce Ale?"

There's an open bar with food from Fette Sau, Little Baby's Ice Cream, Han Dynasty and others.

Tickets are $55, available at PhilaScienceFestival.org.