When it comes to real food feuds, nothing touches the heated — or rather, slow-cooked — debate over barbecue sauce. Simmering across regions and generations, this squabble is like vinegar and, er, ketchup.

"You can carry that metaphor a little too far because it's not as important as religion, but there are these sects and cults," says John Shelton Reed, co-author of "Holy Smoke: The Big Book of North Carolina Barbecue" with his wife, Dale.

The core of the barbecue sauce debate is simple: vinegar-based versus tomato-based.

It's strictly a Southern squabble, the battle line starting with the vinegar crowd in eastern North Carolina. As you move west, tomatoes take over. And the closer you get to Texas, the sweeter and darker red the sauces get.

But for non-Southerners, it's hard to understand the fuss over a sticky substance spread over a chunk of meat.

It has to do with roots.

With origins in colonial times, American barbecue became ingrained in Southern culture in the wake of the Civil War as black pitmasters honed a craft learned during the days of slavery. They became experts at cooking pigs, tweaking the standard vinegar and tomato-based varieties to create region-defining styles.

Uniquely Southern as moonshine, barbecue has become a badge of identity, your sauce preference saying much about where you're from.

"The basis of barbecue is smoke from wood fire, and that seems almost elemental, that it's God-given," says Southern food historian John T. Edge.

"It's the trademark sauce or lack of sauce that a pitmaster adds that becomes their stamp, their place, their tradition, their family. That lends itself to provincial arguments."

The smack talk over which is bet-ter started almost the day German settlers had the audacity to add tomatoes to their sauce, each side acting as if eating the wrong kind is an affront to morality.

Before we get too deep into the sauce, let's be clear about something — tossing a couple T-bones on your rinky-dink hibachi with the wobbly legs and charcoal brickets isn't barbecue.

The manufacturer may call it a BBQ. Your recipe may even call it that. But that's really grilling. And to suggest otherwise might get you grilled by true barbecue aficionados.

Unlike the torch-and-flip of grilling, barbecue is a more laborious process: cooking at low temperatures for hours, turning the meat into a succulent, fall-off-the-bone mouthful of tastiness.

Not surprisingly, the concept goes back centuries.

Homer — the poet, not the cartoon character — refers to a form of barbecue in his epic works, and the term generally is believed to be a derivative of "barbacoa," a West Indian word used to describe slow-cooking meat over hot coals.

Since then, barbecue has morphed into an art form. And the culinary epicenter of this art is in the South, where they've been barbecuing since settlers first wandered into Virginia — and debating sauce styles for nearly as long.

Proponents of the vinegar-based variety claim theirs is the way barbecue was intended, a 200-year-old original not all that different from what Thomas Jefferson ate. A little cider vinegar, some red pepper and a dash salt is all you need.

"We have an old theory that you don't put vinegar on beef and you don't put ketchup on pork," says Wilber Shirley, owner of Wilber's Barbecue, a vinegar-style joint in Goldsboro, N.C., where the specialty is barbecued pork.

"If you get a steak, you put steak sauce or tomato ketchup and this kind of thing. Pork, there's always been a theory that you're not supposed to do that."

This vinegar idolatry, though, doesn't translate very far outside eastern North Carolina.

Starting around the Piedmont region of central North Carolina, barbecue sauce is made with ketchup or tomato paste to add tanginess and color.

The split runs roughly along a line through the Raleigh-Durham area, vinegar-based to the east, tomato-based "Piedmont" or "Lexington" style to the west.

Other than a band of mustard-based sauce around central South Carolina and northern Georgia, the sauces generally get sweeter the farther west you go, places like Memphis and Texas adding molasses or brown sugar to give it a little twang.

Fans of the tomato-based style don't understand how someone could ruin a piece of meat with vinegar, believing a little ketchup makes the barbecue sweeter, prettier, taste better. Save the vinegar for cleaning, they say.

"Everybody has an opinion on what barbecue is supposed to taste like," says Ollie Gates, owner of Gates Bar-B-Q, a tomato-based place in Kansas City, Mo.

"It tastes like what you originally tried in the beginning when somebody told you that was barbecue, so you compare everything to that taste."