Vietnamese island guards a national treasure: Fish Sauce
The pungent, fermented nuoc mam sauce from Phu Quoc
is a staple of the country's cuisine.

FINAL TOUCH: Nguyen Thi Le fills bottles with fermented fish sauce on Phu Quoc Island. SIMON MONTLAKE

PHU QUOC, VIETNAM - Nguyen Thi Tinh draws a sample of her 2006 vintage from a wooden vat, inhales deeply, and dips her finger into the golden-brown liquid. The verdict? A sharp nose. Nice warm hues. And the taste is, well, sour, salty, and unmistakably fishy.What cognac is to France, so the pungent, fermented fish sauce in Ms. Tinh's vats is to Vietnam: A national treasure that shouldn't be produced anywhere else. And everyone agrees that the best fish sauce, or nuoc mam, comes from the island of Phu Quoc. The islanders use only top-grade black anchovies, natural inputs, and traditional storage methods to make their sauce, as they have done for a century or more.

Wherever you travel in Vietnam, you're never too far from a bottle of fish sauce. It's a protein-rich staple of the cuisine, and a constant companion to any savory dish. Other Southeast Asian countries like Thailand and Cambodia produce their own sauces, but nobody does it quite like the Vietnamese.

"Every morsel that people put in their mouths is either cooked in fish sauce or dipped in it," says Ashok Mittal, vice- president of Unilever Vietnam's food division, which sells fish sauce from Phu Quoc under its German subsidiary, Knorr.

But Phu Quoc is changing, and so is the fish-sauce industry. Until the 1980s, when Vietnam began to tinker with its socialist economy, producers sold their sauce to the government at a fixed price. Private traders then took over. As demand increased, more families entered the business. Today, there are more than 80 producers on the island.

Producers began to complain, though, that traders on the mainland were diluting their premium product with low-grade fish sauce and passing off the result as Phu Quoc sauce. Eventually, Vietnam's government took notice. In 2001, it ruled that only sauce produced and bottled on Phu Quoc could use the island's name, giving it the kind of territorial copyright that European wines and cheeses enjoy.

Enter Mr. Mittal's Unilever, an Anglo-Dutch consumer-brand company. Unilever built a $1 million bottling plant on Phu Quoc in 2002 and began selling Knorr-branded fish sauce in Vietnam. The move upset some traditionalists who asked why a multinational was marketing a national treasure, but producers saw a way to get better returns from their sauce.

"Knorr is the first attempt to brand a commodity that's like salt and sugar in Vietnam. It's so integral to daily life," says Mittal.

Today, about one-third of the island's top-grade sauce, or 2,500 tons, is sold under the Knorr brand in Vietnam. But the government hasn't kept up its end of the bargain, says Mittal, as companies that buy in bulk and bottle on the mainland continue to use the Phu Quoc name.

The industry also faces the issue of sustainability. Fishermen are finding it harder to catch the prized black anchovies in the waters around Phu Quoc and are forced to sail further afield. "We have so many fish- sauce manufacturers. I think in future it will be hard to find enough supply" of fish, says Pham Huynh Quoc, who inherited a medium-sized sauce business from his mother.

But there's a new game in town: tourism. In recent years, as newly affluent Vietnamese take more vacations, beachfront property on Phu Quoc is being turned into resorts. The island is abuzz with rumors of foreign investors snapping up land, and local officials are promoting Phu Quoc as the next big destination for holidaymakers in Southeast Asia.

Both Mr. Quoc and Tinh have joined the rush by opening their own hotels, where guests can also buy bottles of private-brand sauce. Both hotels are close to the beach – and far from the pungent vats of fermenting fish.

Inside the open-air warehouse where the sauce is prepared, dozens of tall wooden vats march along the concrete floor. The handmade vats are 10-ft in diameter and can hold several tons of tiny, briny anchovies, which the boats haul in from in the waters off Phu Quoc. For every three tons of fish, a ton of sea salt is added, before the container is sealed at the top. After one year of fermentation, the first extract is sampled – a process that is akin to the first pressing of olive oil.

Traditionally, this is women's work. "Every housewife here knows how to make fish sauce. The husband would go out to fish, and the women would stay home and make the sauce," Tinh says.