IN HEAT like this, there’s nothing better than an ice cold beer – a crisp, tonsil-chilling, sweat-erasing lager served in a frosty mug.

There’s nothing better unless, of course, you actually prefer to taste your beer. Excessive cold deadens the taste buds and masks much of a good beer’s flavor.

And therein lies the great dichotomy of our favorite adult beverage: Do we drink it for refreshment or flavor?

The conflict is never more pronounced than during a Philadelphia heat wave, when bartenders from Eastwick to Bustleton Avenue turn down the thermostats to near-freezing levels and promise “the coldest beer in town!”

I suppose we should thank them for the humanitarian gesture. Except they’re practically ruining many of their beers, namely ales. These brews, with their subtle malt flavors and fruity ester aromas, damn near die of frostbite.

According to Martin Schuster, president of the Draught Beer Guild, the optimal temperature for most industrial lagers is 38 degrees. “The main reason is, for most lagers, that’s the best temperature range for releasing the most bouquet and flavor… But when you get into serving ales, the temperature range should slide up from there” toward 50 degrees.

“The problem is,” Schuster said, “when you get into the 42-degree range for Bud, Miller, Coorsand a lot of other lagers, the beer doesn’t present itself as well.”

Meanwhile, the flavor of ale – especially hoppy varieties balanced with subtle malts and fermented with ester-producing yeasts – is suppressed at cooler temps.

If you don’t believe it, try knocking down the remains of a 16-ounce can of Milwaukee’s Bestthat’s been sitting around for more than a half-hour. The bouquet is rather like the bottom of your hamper.

Likewise, the flavor of a hearty beer, like Victory Storm King Imperial Stout , is virtually absent under 40 degrees. Let it sit in a glass for even as long as an hour, though, and it explodes with a huge range of roasted, fruity flavors and aromas.

Bruce Bryant, a senior research associate at University City’s Monell Chemical Senses Center, said there’s some basic chemistry at work here.

“When the temperature goes down,” Bryant said, “the flavor is actually decreased because the chemical compounds that give beer its flavor are less volatile at low temperatures… It really makes for a less-flavorful beer.”

At warmer temps, he said, these volatile compounds evaporate and enter the nose through the back of the mouth. That’s where most flavor is detected.

Since a bar would need separate cooling systems to serve ales and lagers at their proper temperatures, guess who loses this battle. Ale-lovers just have to ask for unfrosted glasses and wait for their beers to warm up.

Except, the problem is getting worse.

Lately, big beer-makers have launched a cold war.

Coors Light, notably, urges us to “Taste the cold.” Millerreplies that it’s beer is “cold-filtered.”

Meanwhile, in Canada, Labattis marketing the Cold One, a new insulated beer can designed to slow down heat transfer from your hand. And Molsonthis year introduced its new Sub Zero beer-dispensing tower that serves beer at -2 centigrade. (That’s 28 degrees Fahrenheit, or about 5 degrees warmer than the freezing temperature of most beer.)

Even Guinness Stout, a beer that most experts say should be enjoyed in the high 40s, has dropped its suggested serving temp to 43.

Some skeptics believe the colder temps allow brewers to use cheaper, less flavorful ingredients and adjuncts like rice and corn.

Perhaps, but more importantly the chilling effect is plainly designed to mask bitter flavors that many drinkers – especially younger ones weaned on Coke – just don’t enjoy.

At 32 degrees, Bryant said, beer is cold enough to temporarily shut down the nerves in your tongue, where you’d normally detect bitterness. “It’s essentially anesthetizing your mouth,” Bryant said.

Those who actually savor the complex flavor of a well-made ale may cry heresy. But as Schuster noted, “American beer drinkers are conditioned to colder beer, and that seems to be more important to most customers than how those beers should taste.”

You really can’t blame bartenders for turning down the thermostat. “If you want to sell beer on the beach in August,” Schuster said, “you better be selling darn cold beer.”

How cold should you go?

In the Czech film “My Sweet Little Village,” one character found the optimal temperature on the seventh step down to the cellar.

More specifically, here are the serving temps recommended by brewers:

• Carling Extra Cold, 36.
• Heineken, 38.
• Hoegaarden, 39.
• Budweiser, 40.
• Barney Flats Oatmeal Stout, 40-45.
• Guinness, 43.
• Troegs Mad Elf, 45.
• Lindemans Framboise, 45.
• Allagash Grand Cru, 45-55.
• Weyerbacher Insanity, 45-50.
• Unibroue La Terrible, 52.
• Orval, 55
• Pike Pale Ale, 55
• Samuel Smith Taddy Porter, 55
• Three Philosophers, 50-60

Beer radar

Remember the Samuel Adams’ Beer Drinker’s Bill of Rights I mentioned here last time around? The Boston brewery is facing heat over its declaration that beer should be served in bottles. Oskar Blues Brewery, whose Dale’s Pale Aleis canned, says it’s a myth that cans impart a metallic flavor…

Meanwhile on the topic of proper serving temps, the same Bill of Rights decreed that “beer should be served at 35 degrees to 42 degrees for maximum flavor.” At those temps, Samuel Adams’ own $100-a-bottle Utopias would taste like a $1.75 forty of Colt .45…

The Tippler’s Tour is up and running again this summer on Thursday afternoons. It’s a 90-minute, beer-enhanced walk around Old City’s Colonial drinking spots. Call 215-629-5801 for details…

Congrats to Iron Hill brewpub for its decisive win at the Royal Stumble, the annual beer showdown at Nodding Head Brewery. This year’s event featured brewers dressed as comic book heroes pouring mass quantities of craft beers. Iron Hill  Belgian Witwas the first keg to kick…

Destiny Brewing, a new brewpub in Phoenixville, is set to open officially on Aug. 20 in the home of a former Moose lodge that was conveniently outfitted with a bomb shelter…

Minnesota’s Summit Brewing is sending its beers the Philly way. In addition to its well-regarded Great Northern Porter, look for its pilsner, hefeweizen, pale ale and extra pale ale in stubby bottles. Also new on area shelves: Brok  beerfrom Poland, Middle Ages 10th Anniversary Aleand Legacy Hedonism Alefrom Reading.

Beer calendar

Thursday: Beer and cheese dinner at General Lafayette Inn & Brewery (6461 Germantown Pike, Lafayette Hill). An eight-course dinner matching artisanal cheese and craft beer. 7 p.m., $64.95, 610-941-060l.

Thursday: Victory Brewing beer and BBQ at Coleman Restaurant (Normandy Farms, Route 202 and Morris Road, Blue Bell). 6:30 p.m., $24.95, 215-616-8500.

July 29 and 30: Summer brews dinner at the Farmhouse (1449 Chestnut St., Emmaus). John Hansell, editor of the Malt Advocate, hosts the event, pairing a five-course seasonal menu with a variety of beers. 7 p.m., $75, 610-967-6225.

 Joe Sixpack, by Staff Writer Don Russell, was written this week with a glass of Hacker Pschorr Alt.

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