On the morning of my visit to Rawduck, there has been a small — but rather pungent — explosion. Carbon dioxide produced overnight by the bacteria in a jar of fermenting daikon and ginger built up so much that it forced the liquid surrounding the vegetables to make a rapid escape. A mouldering smell bastes the air.
This is not uncommon at Rawduck, a restaurant in east London that specialises in ferments and pickles. Its three founders, Clare Lattin, Tom Hill and Rory McCoy, are evangelical about fermentation, and this month will open a dedicated “picklery”, which will sell fermented goods by the jar.
“When I wake up in the morning, I crave something from a Kilner jar,” says Lattin. Hill recommends kimchi (a hot fermented cabbage from Korea) on eggs for breakfast.
When Rawduck opened in 2014, the menu’s fermented options were not the most popular. Only James Lowe, the adventurous head chef at Lyle’s in Shoreditch, would order their kombucha, a drink made from fermented tea. Today they sell eight to 10 litres a week of it.
The only other London restaurant dedicated to fermentation is Flat Three, a Japanese-Korean-inspired place in Holland Park. “Other chefs are playing it a bit safe,” says Pavel Kanja, the head chef there.
The process isn’t new. Anything that has undergone a form of chemical breakdown by bacteria, yeast or other microbes — from blue cheese to sourdough bread — is fermented. Traces of alcohol have been found on shards of pottery dating back to 8000BC. But it is foods containing beneficial bacterial cultures that have got chefs excited; and the global market for these “probiotics” is fizzing. According to one report, it was valued at $35bn in 2015 and is expected to exceed $64bn by 2023.
To ferment, a food needs to be put in an airless environment (a sealed jar filled with liquid, for example) in which microbes are encouraged to feed off its natural sugars. The result is an acid that both kills off harmful bacteria and transforms the original food. Put cabbage in brine and the result is soft, tart sauerkraut. Ferment soy beans, as they do at Flat Three, and the result tastes a bit like a raisin.
Experimentation is everywhere. “There are some chefs in the US and Scandinavia, like René Redzepi, who are doing funky stuff with fermented insects, peas, pretty much anything they can get to rot safely — even pork tenderloins,” says the food writer Michael Booth.
In an early trial at Flat Three, Kanja incubated koji, the fungus most widely used to make soy sauce, in an oven for two days. “When we first tried serving it on noodles, people thought it was fertiliser,” he says.
The first ferment to make it on to the menu when they opened in 2015 was fermented cauliflower leaves, which are distilled into a broth to accompany poached sea bass. The result is rather like fragrant seawater. Another success was celery in fermented buttermilk, served last Christmas. One customer kept returning for it, despite the £12 price tag. “She said she had never tasted celery like it,” says Kanja’s wife Claire, the restaurant’s sommelier, who tried 250 wines before finding those “funky” enough to withstand the powerful flavours.
Working through the tasting menu, few dishes fail to raise eyebrows. The initial acidic tingle of roasted white kimchi, fermented at 17C in the wine cellar before being grilled to enhance the umami flavours, develops into a mellow, charred taste. A hopless beer with a sprightly tang of apricots is made of only bergamot and hogweed. The rare sirloin of aged beef is less appetising, perhaps. The night I tried it, it tasted of Stilton rind.
Flavours aside, fermentation has other benefits. It helps to preserve things, speeds up cooking times by “pre-digesting” certain nutrients and, most popular among food bloggers and manufacturers, it is thought to be good for our insides.
Search “fermented food health” online and up pop its immunity-boosting properties, its potential to cure depression — even to alleviate stress. Research suggests that an increase in the diversity of bacteria in our gut can enhance our metabolic activity but nothing is proven. Studies of our microbiome — the two kilos worth of bacteria that we carry around in our colon — are at the embryonic stage.
“We only really discovered that the microbiome existed 20 years ago and the technology to investigate it has only become good enough in the last five,” says Dr Tim Spector, a professor of genetics at King’s College London and author of The Diet Myth. In 2014, Spector helped establish a crowd-funded project to study the gut. As well as fending off pathogens, he says the bacteria in fermented foods trigger the microbes in our digestive system to produce healthy chemicals. “Even if the bacteria don’t stay in your gut, the effect that they have is positive.”
Japan, which has the highest life expectancy in the world at 83.7 years, is a case in point. Booth, who dedicated a chapter of his book, The Meaning of Rice, to the mould koji, calls the Japanese “the kings of fermented foods”. “Miso soup is my go-to hangover cure,” he says. “I am totally convinced of the benefits of naturally fermented foods and I do think it is one of the reasons why the traditional Japanese diet is so good for you.”
‘Casu marzu’, an Italian cheese infested with maggot larvae, is ‘naturally creamy and pungent’
Not everyone is persuaded. Matthew Ciorba, a professor of gastroenterology at Washington University, has said that there is no evidence that people with healthy digestive systems can reap benefits from fermented fare. Even the trio at Rawduck admit that eating too much of it can make them feel more bloated than they’d like.
Certain delicacies are not for the faint-hearted. Roberto Flore, head of culinary research at the Nordic Food Lab, an incubator set up by René Redzepi in 2008, says his favourite fermented food is casu marzu, an Italian cheese that is infested with maggot larvae. It is, apparently, “naturally creamy and pungent”.
Unlike Flat Three, where Kanja appears to delight in the possibilities of fermentation for its own sake, the Food Lab’s aim is to re-educate western tastes. “Too much time is spent just describing fermentation for its health benefits,” says Flore. “We want to take a wider perspective about how it can improve diversity of taste and keep our palate excited and healthy.” After 60-odd years of processed food and what Sandor Katz, whose book The Art of Fermentation is a bible for ferment practitioners, calls the “war on bacteria”, Flore’s concern is that our tastes have become too beige.
Back at Rawduck, I am given a forkful of the exploding daikon and ginger. Florid orange in colour, it has a soft crunch and a gratifyingly warm flavour. Just a mouthful gets the saliva going — one reason that the team recommend pickles as a starter.
Hill pulls open a different pot — another strong whiff. This time it is week-old spring greens fermented with jalapeños and soy. Lattin and McCoy crowd around. “Absolutely gorgeous,” Lattin proclaims. I sniff the proffered fork and try it. Against my nose’s better judgment and my mouth’s initial surprise, I have to say she’s right.
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Photographs: Charlie Bibby
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