Foundations of Flavor: The Noma Guide to Fermentation

by René Redzepi

There are numerous biological processes at work in any given fermentation, but the ones that matter most to us from a taste perspective are those that break down large chains of molecules into their constituent parts.

The idea is basically to give the substance you intend to ferment a boost of beneficial microbes by adding a dose from a previous batch of that same ferment.

Ceramic, glass, and metal containers and utensils can be baked in the oven for 2 hours at 160°C/320°F to ensure that they’re free of contaminants.

At Noma, for large items like crocks and buckets, we disinfect using ethanol diluted with filtered water to 60 percent alcohol by volume (ABV)—40 milliliters water for every 60 milliliters ethanol. (We dilute it because if the percentage of ethanol is too high, it can actually coagulate the proteins that make up the cell walls of many microbes and prevent them from dying.) We put the solution in a spray bottle and spray whatever needs to be sanitized, let it sit for 10 to 15 minutes, then wipe it off with a paper towel.

If a ferment reaches a pH below 5 within the first two days and ends up below 4.6 by the time of completion, it is generally recognized as safe.

Thankfully, lacto-fermentations are also incredibly straightforward to make. The process is simple: Weigh your ingredient, add 2% salt by weight, and wait.

This could be the key point to all lacto ferments.

Every September at the restaurant, at the end of the berry season, we lacto-ferment blueberries, raspberries, mulberries, blackberries, white currants, and pretty much any other soft fruit we can get our hands on. Even though it lacks the crunch of a fermented root vegetable, the finished puree-like mash is a prize in itself—both sweet and savory, with multiple layers of sourness.

Because the berries usually lose their shape and texture when lacto-fermented, we often use a juice press to harvest the juices. Fermented berry juice is incredible—it has body and effervescence, saltiness, sweetness, and acidity. Mix fermented raspberry juice with a spicy olive oil, add a few grinds of floral spice—maybe long or pink peppercorns—and spoon the resulting vinaigrette over thick slices of ripe beefsteak tomatoes. Sprinkle it with sea salt, sugar, and a few torn leaves of marjoram, and it’s the perfect distillation of late summer. And don’t throw away the berry pulp. It will bring nuance and brightness to a bowl of fresh berries, topped with freshly whipped cream.

At Noma, we start our lacto-fermentations with 2% salt. It’s enough to dissuade any malevolent bacteria from taking hold, but not so much that the product becomes unpalatably salty.

Softer fruits will begin to dissolve in brine over the course of a few days, but crunchier vegetables of manageable size (beets, radishes, or young carrots) do extremely well submerged in salted water.

When lacto-fermenting in brine, start off by placing your empty crock or jar on a scale and taring the scale. Next, place your vegetables in the vessel, making sure they fit snugly without being squished. Cover the vegetables with enough water to fully submerge them, and note the total weight of the contents. Calculate 2% of that weight, and measure that much salt into a mixing bowl. Pour the water out of the vessel into the mixing bowl and blend until the salt is completely dissolved, then pour it back into the vessel.

If you’re especially concerned with maintaining pickle crunchiness, adding tannic plant leaves—like grape or horseradish leaves— to your brine or using mineral-rich unrefined sea salts or alum can reinforce the pectin in the plant walls and keep them snappy.

Try replacing 5 to 10 percent of the water in a brine with fruit juice to inject brightness while supplying additional sugar for LAB to ferment.

For spice, add a knob of horseradish or a halved chile.

Onions and turnips lacto-fermented with a fistful of aromatic herbs like lemon thyme or orange blossom can elevate a dish of ceviche with floral notes and a crisp textural contrast.

Overfer-mented fruits or vegetables tend to have a sameness about them, where the original character and flavor of the product is washed away under a sea of sharp acidity.

Gauging when a fermentation is ready is no different from knowing when your pasta is perfectly al dente, or a floret of broccoli is properly blanched. As Thomas Keller once said, “Put it in your mouth and eat it.” The only way to check on the progress of a lacto-fermentation is to taste it.

Weigh the pitted plums and calculate 2% of that weight—this will be the amount of salt you’ll add later. For example, if the weight of your pitted plums is 950 grams, you’ll need 19 grams of salt.

If fermenting in a jar or crock: Cut the plums in half two more times, into 8 pieces each. This will allow the plums to fit more snugly into the fermentation vessel and eliminate air gaps between pieces. Place the fruit in a bowl, add the salt, and mix well. Use a rubber spatula to scrape the plums and salt into your fermentation vessel of choice—make sure to get every bit of juice and salt.

At 28°C/82°F, our plums usually take 5 days to ferment to the ideal flavor. At 21°C/70°F, they might take 6 to 7 days, but ultimately you need to let taste be your guide.

If fermenting in a crock or jar, look out for a wispy white substance that may form on the surface of the liquid and around the edges of your fruit. This is kahm yeast, a topical fungal bloom that can flourish before your fruit has fully fermented and acidified its juices. Kahm yeast is harmless, but it can add an off-flavor if it gets disturbed and mixed into the liquid. When you spot some kahm yeast, carefully spoon it off and discard.

Tasting the fruit every day will help ensure that you don’t let the fruit overferment.

Once the plums have finished fermenting, remove them from the bag or fermentation vessel, and strain the juice through a sieve into a small container or plastic bag. Depending on the ripeness of your plums, you should have about 125 milliliters juice. The juice is an amazing product that’s already halfway to being a fantastic vinaigrette. Store it in the refrigerator for up to a week

To store the lacto plums themselves, place them in a covered container or a resealable bag. They’ll keep in the refrigerator for up to a week without changing character much,

Kombucha is a soured and lightly carbonated fermented beverage, traditionally made from sweetened tea. Its murky origins are believed to lie in Manchuria (what is now northeastern China) around 200 BCE. From there it spread east to Japan, largely through the efforts of a fabled Korean physician named Kombu. Hence, kombucha (cha being Chinese for “tea”).

Almost any liquid with enough sugar can be fermented into kombucha, so while it’s customary to make kombucha from sweetened tea, some of the varieties that we enjoy most are made from tisanes (herbal infusions) or fruit juices, which yield a roundness and depth of flavor not found in tea. We’ve made great kombucha from infusions of chamomile, lemon verbena, elderflower, saffron, and rose, as well as from the juice of apples, cherries, carrots, and asparagus.

We take advantage of the same idea in our own way at Noma. Using a common air pump—the kind you’ll find in the aquarium section of any pet store—we send air through our would-be vinegar, providing AAB with the oxygen they need to work quickly. By treating our bacteria as if they were pet goldfish, we can cut our fermentation time from a few months to a couple of weeks.

Of the twenty amino acids that our bodies require to function, there are nine that we can’t produce on our own. Soybeans are one of the few plant foods on earth that contain all nine of these essential amino acids.