Only 10 to 15 restaurants in the South still cook hogs the slow way, over wood, according to John T. Edge, director of the Southern Foodways Alliance, a food group that is on a mission to save the traditional barbecue.

"Barbecue is our great American folk food," he said. "Barbecue at its most intense is more than a food. It's an event at which people gather. It's a totem of identity."

Southerners call the celebratory gathering to eat pork pulled from the carcass a "pig pickin." Quicker cooking methods like gas, electric or coal cookers are ignored in favour of slow roasting.

The Oxford, Mississippi-based Alliance, which was founded in 1999, documents the South's culinary history and traditions. Over the last decade, it has made 35 documentary films and taken almost 700 oral histories about Southern food from barbecue and boudin to Gulf Coast oysters and Mississippi Chinese groceries.

"The American South is certainly the heartland of barbecue in America and yet there are so many expatriate Southerners who are now cooking with wood and cooking well across the country," Edge explained.

"There are other cultures, other peoples who cook something we might recognize as barbecue: jerk chicken from Jamaica or other culturally inspired forms."

ORAL RECIPES

Bernard Herman, professor of American studies at the University of North Carolina at Chapel Hill, described it as a "barbecue diaspora."

"The U.S. as a whole is far more Southern now than it was 50 years ago. Look at music. Look at certain forms of religion," he added.

To document the Southern barbecue tradition, two Alliance researchers travelled to South Carolina and North Carolina on a Southern Barbecue Trail. Food historian Rien Fertel, 32, and photographer Denny Culbert, 27, traversed the Southern states in their Barbecue Bus, complete with a bumper sticker saying "Oink if you love barbecue," to visit restaurants still cooking whole hogs over oak and hickory coals.

"Some are 70 or 80 years old and are still owned by the original families," said Fertel, adding that their cooking methods and sauce recipes have been handed down orally.

Skylight Inn in Ayden, North Carolina, and award-winning Scott's Bar-B-Que in Hemingway, South Carolina were among the restaurants they visited. Rodney Scott, pit master and owner of Scott's, inherited the 40-year-old business from his family.

Like the artisanal wines and cheeses of France that vary from region to region, barbecue methods and sauces differ from county to county in the South, Edge said.

"Drive 50 miles (80.4 kms) and the barbecue changes," he added.

And in some places pork isn't even on the menu.

Barbecue in Texas means beef, said Herman. In western Kentucky, it's mutton and in parts of Mississippi goat is the preferred meat. Some barbecue restaurants also add turkey to their menus.

Louisiana has no barbecue tradition at all, according to Fertel, who was born and lives in Lafayette.

"Barbecue is somewhat exotic to me," he explained.

The rural pit cooking method goes back to American and Caribbean Indians and Southern plantations where pigs were roasted over embers at the bottom of a trench dug in the ground. It was a way to feed a large number of people at one time, according to historians.

"This is a food where much of the expertise resides with African-American cooks," Edge said. "The old pit masters of the South carry on large and proud traditions."

Edge added that they are arguably as talented as cooks preparing food in white tablecloth restaurants, and their stories are heroic in the truest American form.

"These are men and women who, post-emancipation, found their way into the economy and found a way to support their families by digging a hole in the ground, laying in bed springs, topping those bed springs with roofing tin and calling that a pit," Edge said.

"There are still people who dig holes in the ground to cook barbecue," he added, "but now that's more likely to be Mexican-American immigrants cooking barbacoa." (Editing by Patricia Reaney and Kenneth Barry)

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