Vietnamese food is nothing without the imprint of fish sauce (nuoc mam). The best Vietnamese fish sauce is delicately flavored and full of umami goodness. Believe it or not, good fish sauce can be enjoyed straight. Seriously! You can make fish sauce from various kind of aquatic animals (shrimp, mackerel, or squid, for example). However, the best Vietnamese fish sauce comes from the island of Phu Quoc, where the waters are full of a particular kind of anchovy called ca com.
What you expect
Like wine in France and olive oil in Italy, fish sauce is the prized staple of Vietnam, where it is used in soups and marinades or diluted into a sauce that accompanies foods from spring rolls to noodles. The Vietnamese have seals on their bottles to indicate quality, the highest being nuoc mam nhi, the first extraction of liquid from fish fermented in salt: extra-virgin fish sauce, if you will.
And the best of the best, as widely agreed among Vietnamese enclaves around the world, comes from Phu Quoc, a tropical island off the nation’s southwest coast. In fact, the Phu Quoc name is so coveted and abused in the fish sauce industry that local producers have been working with the World Trade Organization to protect its appellation of origin.
Curious as to what made Phu Quoc fish sauce so legendary, I made my way to the fabled island this winter to taste it for myself.
Fish sauce factory
Frankly, there isn’t much romantic about the Khai Hoan fish sauce factory I visited there. About 10 feet from the factory entrance, the acrid odor hit me: a dense, stifling smell, almost like rank sweat. Forging onward, I made my way into a tall room with floating rafters, underneath which stood row after row of hulking wooden vats, each with a spigot on the bottom to drain the juices. The giant barrels were filled with the amber-colored liquid, some with a crusty orange film that had settled on top.
At the factory storefront, a worker handed me a bowl of fish sauce and a straw and motioned for me to sip. A few drops filled my mouth with a pungent, robust meatiness. The flavor was rich and complex, like pure essence of cured meat compacted and liquefied.
Making the sauce requires three parts fish to one part salt, a ratio common to most producers in Southeast Asia. Anchovies or other tiny fish usually are used; larger, more expensive fish such as mackerel or sardines can be substituted but result in a costlier, less profitable product.
After about a week, liquid begins seeping from the fish and is drained and circulated back into the vat every day for an entire year — long enough for it to reach concentration, but not long enough for hydrosulfuric acid to appear, which would spoil the taste.
This first extraction is the highest quality, reserved for direct consumption in dips and sauces. Subsequent extractions are produced by running sea water through the vat, which results in a weaker, lower-grade product normally used for cooking.It’s a process that hails from ancient times and is not confined just to Asia. The Romans used a similarly fermented fish liquid they called garum, which appears in nearly 350 recipes in Apicius’s classical Roman cookbook, “De Re Coquinaria.” Pompeii later became famous for its production of the condiment, and even now, a fish sauce called colatura remains a specialty of Cetara, a village on the Amalfi Coast of Italy, where locals toss it with pasta and garlic. In the East, fish sauce is likely to have come from China or Vietnam as a way of preserving fish. Some speculate that the Chinese often mixed in soy beans as filler, and because more of the population in China lived away from the coast, soy beans became more common than fish, eventually leading to the soy sauce now associated with Chinese cuisine.
At the factory in Phu Quoc, the workers lined up the bottles of fish sauce by gradients of color, like tea steeped to varying degrees. The darkest-colored bottle was labeled “43°N/1L” and came from the first extraction of liquid. The others bore decreasingly lower numbers — 40, 30, 20 and 15°N/L — and came from subsequent extractions, after water had been added.
The secret recipe
It took some digging to find someone who could explain those numbers and the science behind them. But after several phone calls, a bit of networking and a flight back to Ho Chi Minh City, I found myself walking into a squat, concrete Soviet-era-style government building, where, in a classroom full of cramped desks and chairs, I finally met my fish sauce guru.
“Good nuoc mam should be transparent. You should be able to see the other side of the bottle,” said Nguyen Quoc-Thiet, a researcher at the Vietnam Academy of Science and Technology who gave me a personal, hour-long lecture with the intensity and expertise of a sommelier.
“It tastes salty at first, but the aftertaste is sweet,” he said.
Nguyen comes from An Thoi island, a cluster of islands on the southern tip of Phu Quoc, where his family has worked in the fish sauce industry for three generations. His grandfather began working at a friend’s factory in the ’40s, and every time he saved enough money, he bought one of the large wooden vats, hoping to some day start his own business.
The vats back then were made from a tree indigenous to Phu Quoc and were believed to impart a special flavor to the liquid, “like oak to wine,” Nguyen explained. Known as boi loi, the tree is found only on Chua, or “God,” Mountain in the Phu Quoc National Park and has become endangered and illegal to cut down. By the time Nguyen’s grandfather died, he had 100 such tanks that he bequeathed to his 10 children.
Pursuing that family legacy, Nguyen wrote his undergraduate thesis on fish sauce and went on to receive his PhD in organic chemistry. When asked about the figures measured in °N/1L on the bottles at the factory, he launched into a dense 15-minute lecture that included hand-scrawled flowcharts and molecular formulas. What the number boils down to, Nguyen explained, is the degrees of nitrogen content per liter, a figure that denotes the concentration of fish protein in each drop. While protein is solid, the process of fermentation breaks down the protein’s amino acid bonds, of which nitrogen is a main component.
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