Is freshness overrated?

I’ve been making kimchi—the Korean dish of fermented spicy-sour cabbage—for a couple of years, ever since tasting a friend’s homemade batch in early 2016. Lacto-fermentation was trending at the time, and countless gastronauts and chefs were making kimchi and sauerkraut and serving it as a garnish or side dish.

But fermentation hardly stops at cabbage—just about anything edible can be transformed by placing it in a jar with salt or brine and letting molds, yeasts and bacteria do their thing. Kombucha, kefir, yogurt, beer, wine, sourdough and miso are all made by fermentation.

While exploring different kimchi recipes, I noticed something: many called for fermented shrimp paste. Curious about fermenting animal matter, I did some research. I discovered that beyond the trendy world of cultured tea, milk and veggies, there is a less explored, almost morbid, realm where bacteria and enzymes are cultured in flesh, blood and offal, mainly of fish.

Of all the literature on fermented fish, most focused on garum, an umami condiment essential in Asian cuisine and, long ago, prized by ancient Greeks and Romans. According to historical texts, Romans made garum by putting salted fish, guts and all, in clay pots for months to bake in the sun. Eventually, they strained a strong-smelling, honey-hued liquid from the ripened mash.

In these products, wonderful things happen: Enzymes originating in the fish convert fats and proteins into a variety of acids, which help preserve the flesh. The chemical changes, assisted by bacteria, also produce powerful aromatics that people either loathe or love. Canning and freezing have largely made these methods obsolete, but they are seeing a modern revival among gourmands.

I wanted a taste of this wilder world of fermented things, and when my brother and I lucked into a bounty of fresh anchovies (more than 100 pounds), I saw my chance. Following a basic garum recipe, I filled a couple of mason jars with fish heads, gills and innards. I poured in a heavy dose of kosher salt, thoroughly stirred the mixture, and put the jars in my backyard.

Over several weeks, the fish solids settled into a reddish-amber liquid. The transforming sludge, though it was baking in the summer sun, did not smell the least bit foul. Rather, at week four, it was redolent of miso, onion and, well, salted anchovy.

Four months later, I strained the liquid and it was gorgeous—maple-colored and clear of particles. Held to the sunlight, it glowed. However, I had recently read that botulism can grow in environments of less than 10 percent salt. Since I had, for no reason except rookie error, neglected to precisely measure the salt additions, I was uncertain if my fish sauce was safe to consume. Botulism can be treated, but the damage it causes cannot always be reversed, and symptoms of fatigue and shortness of breath can persist for years. I couldn’t be sure that my sauce had enough salt for safety, so I pasteurized it. The heating process ruined the garum, which coagulated and immediately smelled like burned beans and soy sauce. Heartbroken, I dumped it down the drain.

Fortunately, I soon got another chance when my two brothers, my two nephews and I caught enough herring to fill a cooler. I jarred about 17 pounds of innards and heads and carefully calculated a conservative 20 percent salt addition. Eight months later, I strained out the garum. As a dressing and finishing sauce, it is fishy, gamey and umami—fantastic. A spoonful does wonders for a batch of kimchi.

With fermentation, time becomes a tool and age an asset. Neither fresh nor foul, fermented fish occupies a place in between.