PUBLISHED: 29 MARCH 2016!| ARTICLE NUMBER: 16039 | DOI: 10.1038/NMICROBIOL.2016.39 feature Artisanal food microbiology Arielle J. Johnson Because of their ability to biochemically transform their growing environments, microorganisms are playing a new creative role as a culinary tool, enabling both professional and amateur cooks to create entirely new flavours from existing ingredients. he use of fermentation — loosely defned as the transformation of Tfood by microorganisms — as a means of preserving food goes back thousands of years, if not further. Carefully controlled fermentation processes are key to elaborate well-known delicacies whose culinary absence would be sorely felt, such as cheese, chocolate, miso, wine, cofee, bread, soy sauce, yogurt, beer and pickles. Fermentation and cuisine have a long, well-cemented relationship all over the world (Box 1), but for the most part, these processes have been confned to specialized workshops, such as at a soy sauce producer or vinegar houses, rather than the day-to-day workings of the restaurant kitchen. While it’s increasingly common for restaurants to ofer high-quality bread, made in-house from a purposefully cultivated sourdough starter, the same has not been true of other fermented products that appear on the menu. ARIELLE JOHNSON Tat is, until recently, when cooks around Figure 1 | Arielle Johnson in a soy sauce factory in Saitama, Japan. the world have begun to discover (or, more accurately, to rediscover, drawing from history and other cultures) the possibilities organisms — what one might call ‘culinary kitchen, practically the only time you make of using fermentation processes in the microorganisms’ — are bacteria and fungi. new favour molecules while cooking is kitchen. Call it a revival, a natural outgrowth Lactic acid bacteria (LAB) of the genii through the breakdown and caramelization of the ‘do-it-yourself’ mentality, or artisanal Lactobacillus, Leuconostoc, Pediococcus of sugars by heat, or through the similarly food microbiology; a new appreciation and Lactococcus, produce lactic acid from heat-driven Maillard reaction. Tis process for old techniques and a reinterpretation sugars in products like sauerkraut, kimchi, creates the favours of baked bread and of their uses is transforming the human– yogurt, cheese and miso. Acetic acid roasted meat through the reduction of microorganism–substrate relationship into bacteria (AAB), obligate anaerobes in the sugars and free amino acids. Meat may be a new cooking tool, every bit as essential as family Acetobacteraceae, are responsible aged to develop new favours by allowing a paring knife or frying pan. It is giving chefs for the creation of vinegar. Te yeast endogenous proteases in the animal’s cells new methods for working in concert with Saccharomyces cerevisiae metabolizes to slowly break down proteins and release bacteria and fungi to transform ingredients sugar into ethyl alcohol and carbon in amino acids. Generally, however, the and create new favours. wine, beer and bread, and the salt-tolerant creation of favour molecules occurs at the Microorganisms live in or on their food Zygosaccharomyces rouxii contributes farm, during the process of growing and source, and biochemically transform it to to the toasty, malty favour of soy sauce rearing plants and animals. In the kitchen, extract energy, producing metabolites in (Fig. 1). Useful moulds include Aspergillus the work becomes the preservation, the process. In general, a pool of larger- oryzae, whose amylolytic and proteolytic capture, and rearrangement of these molecular-weight, and usually less favour- activities on grains constitute the building favours through the controlled application active molecules —like starches, sugars, blocks for sake, miso, and soy sauce; and of heat, and generally avoids microbial proteins, and alcohol — are transformed Penicillium roqueforti, which creates the processes, which would commonly be into a more diverse group of tastier, smaller blue-green veins (and pungent favour) of considered to be spoilage. Fermenting for molecules, such as amino acids, organic blue cheeses. favour has not traditionally been an area acids, esters, sugars, alcohols, and aromatic When you ferment something, you of interest for cooks, but adding microbial compounds. Te most commonly used create favour. In a traditional Western transformation to their repertoire can give NATURE MICROBIOLOGY | VOL 1 | APRIL 2016 | www.nature.com/naturemicrobiology 1 ǟ ƐƎƏƖ !,(++- 4 +(2'#12 (,(3#"ƥ ++ 1(%'32 1#2#15#"ƥ ɥ ɥ ɥ ɥ ɥ ɥ ɥ feature Other established restaurants have Box 1 | Cuisinology. also drawn inspiration for their cuisine from working with microorganisms. Katsuobushi. Smoked, dried, fermented Kosho. Short for yuzukosho, a fermented Sean Brock’s restaurant, Husk, takes a tuna that is shaved and steeped with kelp mixture of yuzu citrus peel, chilli peppers similar geographic approach to creative to make dashi, one of the basic broths of and salt, a specialty of the Kyushu region limitation, using only ingredients Japanese cuisine. of Japan. from south of the Mason–Dixon line. Tis means that to put olive oil on his Kefr. A LAB–yeast mixed culture dairy Kvass. A beet- or rye-bread-based menu, he had to fnd a grower in Texas. fermentation originating in the Caucasus fermented beverage popular in Baltic and Combined with childhood inspiration mountain region. Slavic cultures. from Brock’s grandmother, who would ferment sauerkraut, sour corn and Koji. Aspergillus oryzae mould inoculated Miso. A two-stage fermentation technique wines, it also lead to collard greens and grown on grains or legumes, from Japan; the frst stage traditionally uses fermented in the style of sauerkraut, traditionally rice, barley or soybeans. rice, barley, or soybean koji. In the second fermented peppers and a ‘vinegar pantry’ Koji is the Japanese name; the process stage, salt and soybeans are added and with vinegars made from strawberries, originated in the Neolithic period in China secondary lactic fermentation takes place, sorghum and, infamously, Mountain where it was called qu or chhü. Koji is rich yielding a rich, sweet, tangy, salty, and Dew. Likewise, the New York restaurant in amylases and proteases, which makes umami-favoured paste. group Momofuku has a lab devoted to it useful as a catalyst for making other developing new food techniques, and fermented products like miso, soy sauce Tempeh. A cake-like soybean fermentation has devised fermentations inspired by and sake. from Indonesia made using moulds in the Japanese miso and katsuobushi, but made genus Rhizopus. with locally-sourced pork, spelt and Kombucha. An acidic liquid or beverage chickpeas. Bar Tartine in San Francisco, made from fermenting sweetened tea Tsukemono. Japanese term for pickles. helmed by chefs Nicolaus Balla and with a mixed culture of yeasts and acetic Styles include kasuzuke, (pickling with Cortney Burns, features a regular rotation bacteria that form a pellicle or zoogloeal kasu, lefover sake lees); misozuke of lacto-fermented vegetables on its menu, mat. Te origin of kombucha is unclear, (pickling in miso); nukazuke (pickling in with koji ofen making an appearance though Russia, China, Japan and Korea are a bed of nuka, rice bran); and shiozuke, along with a spectrum of fermented all contenders. (pickling in salt). beverages including dairy and water kefr and kvass, all of which are produced in-house. Restaurants have not limited them a new dimension of control over for exactly the species of yeast, bacteria and their creative use of microorganisms to favour, and new avenues for expressing the moulds that we use to make misos, vinegars, fermentation alone — many algae strains, potential of their ingredients. lactic fermentations, kombuchas and other known for their oceanic favours — have As a favour chemist, for the last products (see Box 1). In-house fermented been featured in dishes at Number 9 Park several years I’ve worked on collaborative products play a role in nearly every dish in Boston and Aponiente in Spain, and research with kitchens and restaurants to at noma. Fermentation has become vital better understand the inter-relationship to the menu (as well as to those of many of food and science. In my job as head of other restaurants), because of its ability to research at MAD (a food culture nonproft transform and create favours. Consider and symposium with a close relationship acidity — you might add this to a dish in to restaurant noma in Copenhagen) I the form of lemon juice, or perhaps wine have a broad mandate to use a variety of vinegar, but rule out citrus and grapes, approaches and tools to help all cooks better neither of which thrive in a Scandinavian understand food. Te cuisine of noma climate, and your options are fairly limited. is based around geographical limitation: Turning to the world of microorganisms, ingredients must come (mostly) from the several types of bacteria produce acids Nordic region. As with many limitations, as their primary metabolite, chiefy LAB this has led to a blossoming of gastronomic and AAB. Lars Williams, noma’s head of creativity in the search for favours, with R&D and my lab partner, has spent much fermentation at its heart. My job there is of the last decade developing, exploring to distil technical and scholarly knowledge and iterating these techniques, ‘dialling- from many diferent felds into practical in’ subtle diferences in the quality of knowledge that any cook can use. their acidity and its balance with other Most of our lab is dedicated to favours from the substrate or from fermentation, both development and parallel fermentation products. A dish at production. Inside modifed shipping noma might get its acidity from a favour containers, which we retroftted ourselves, palette that includes fruity and foral wild are seven rooms that function as climate- chamomile kombucha, earthy and tangy AND NOMA ARIELLE JOHNSON controlled incubators, able to hold lacto-fermented mushrooms, a caramelized temperatures between –30°C and 60°C, and and robust reduction of rye miso, and clean Figure 2 | A conceptual recipe for ‘squid garum’, humidity levels of up to 99%.