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date: 18 April 2024

Living Fermented Foods and Drinksfree

Living Fermented Foods and Drinksfree

  • James ReadJames ReadIndependent Scholar

Summary

Fermentation is the process by which microbes transform ingredients into a palatable product or ferment. Its customary uses are food preservation (as in sauerkraut) and alcohol production (as in wine or beer), though it is also highly regarded for flavor enhancement and health benefits. Research into fermentation is multidisciplinary, covering fields ranging from history and anthropology to microbiology and nutrition.

Fermentation has been intentionally employed as a preparation technique through which microbes and humans have domesticated each other for at least 13,000 years, across cultures spanning from Japan (miso) to Mexico (tepache). It is central to many foods and drinks, but when referring to “ferments” in a culinary context, most people do not mean bread, beer, or olives but, rather, the likes of kimchi, kombucha, and kefir. These could broadly be termed as “living ferments,” as they have at least the potential to contain live and active microbes when they arrive on our plate. This quality of vitality is not only merely useful for classification but also for indication of how they are made (such that there is no inherent pasteurization or dehydration to create the final product).

To categorize ferments further, they can be grouped as vegetables (such as kimchi, sauerkraut, pao cai, and gundruk), no/low-alcohol drinks (such as tepache, tejuino, atole agrio, kombucha, and juniper beer), dairy (such as yogurt, kefir, dahi, amasi, and tätmjölk), and soybeans (miso, soy sauce, douchi, koji, doubanjiang, gochujang, tempeh, natto, and meju).

Ferments can be made either by inoculation with a starter culture or by spontaneous (or wild) fermentation. In either case, competition and collaboration within the microbial community results in different species occupying their own niches, some of which are crafted for them through fermentation techniques and some of which the microbes develop for themselves. This adaptation is mirrored on a coevolutionary scale, as humans and microbes have made homes for and of each other.

Subjects

  • Food History and Anthropology
  • Food Science

Introduction

Fermentation is a fundamental food processing technique by which microbes render ingredients more palatable, nutritious, and long-lasting. While fermentation’s customary uses are food preservation and alcohol production, it is also highly regarded for flavor enhancement and health benefits. Research into fermentation is multidisciplinary, and this article aims to provide an overview to the topic, in particular, covering studies in the fields of history, anthropology, microbiology, and nutrition.

Archaeological evidence for intentionally conducted fermentation has been found dating back 13,000 years to the Late Epipaleolithic Natufian culture,1 and it remains central to contemporary foodways ranging from China (soy sauce) to Mexico (tepache). While these earliest extant remains of fermentation are relics of alcoholic production, food fermentation is corroborated not long after, with a large-scale fish fermenting site discovered in Scandinavia from 9,000 years ago,2 and evidence of fermented dairy in the form of cheese from 8,000 years ago.3

Long before humans gained the knowledge to intentionally ferment food, and, in fact, before they were humans, our primate ancestors were seeking it out. A couple of genetic adaptations which are thought to indicate increased fermented food consumption can be traced back to around ten million years ago. The first (the ADH4 gene), allowed for increased alcohol tolerance,4 and the second (HCA3) is a receptor activated specifically by metabolites resulting from lactic acid bacteria, thus allowing for digestion.5 These adaptations allowed for the consumption of overripe, alcoholic fruit, and lacto-fermented foods, implying they were significant within our ancestors’ diet.

Carrigan posits that the reason for this increased consumption of fermented foods is that these adaptations coincide with our ancestors descending from the trees and wandering the forest floor, where fermented windfall would have been found.6 Building on this hypothesis, Katherine Amato and colleagues suggest that this was more than simply scavenging but may have been a targeted approach to use fermentation as a method for predigestion, with the last common ancestor seeking out fermented specimens of otherwise impenetrably tough or toxic fruit, as fermentation typically renders fruit softer and can break down its defenses.7 This may have been the beginning of the journey along which humans and fermentative microbes have domesticated each other—as Eva Rosenstock, Julia Ebert, and Alisa Scheibner note, “dairy Lactobacilli, Lactococci, and Streptococci may be as much domesticates as domestic plants and animals but have not yet been perceived as such in archaeology.”8

Various fermentation techniques create preferential environments for differing microbial communities and consequent end products, which can be termed “ferments.” These can be broadly categorized by the primary biochemical process which acts to preserve them—and indeed, this is primarily the method suggested by Keith Steinkraus—breaking them down into lactic acid fermentation (e.g., sauerkraut), acetic acid fermentation (e.g., vinegar), alkaline fermentation (e.g., natto), and alcoholic fermentation (e.g., beer).9 Steinkraus adds three additional categories which are descriptive of the end product, for “textured vegetable protein meat substitutes” (e.g., tempeh), “high salt/meat-flavored amino acid/peptide sauce and paste fermentations” (e.g., soy sauce), and “leavened breads.” However, in reality, some ferments are created by combinations of these processes that can include an orchestra of different microbes, sometimes working simultaneously and sometimes in sequence, as one strain creates conditions which are more suitable for another and each finds its niche.10 These processes, deployed singly and in combination to act on myriad ingredients, result in a wide variety of fermented foods and drinks. Amongst them are a number which involve fermentation incidentally but where it is not their primary preparation method—coffee, for example, may be processed using fermentation to remove pulp from the cherries—and, indeed, there are fermented foods and drinks that have become so fundamental as to have created their own categories (such as cheese).11 Thus, when one refers to “ferments” within a culinary context, it is generally accepted that one does not mean things such as bread, beer, or brie but, rather, the likes of kimchi, kombucha, and kefir. These could broadly be termed as “living ferments,” as they have at least the potential to contain live and active microbes when they arrive on one’s plate.12 This quality of vitality is useful not merely for classifying but also for indicating how they are made (such that there is no inherent pasteurization or dehydration to create the final product).

While it is helpful to understand the processes underlying ferments, outside of microbiology, it is not always as immediately useful as knowing the food group, flavor, and origin, so instead John Leech and colleagues organize them by substrate—a classification which gives primacy to the food rather than the microbes in the relationship.13 As such, these scientists divide ferments into “brine,” “dairy,” “soy,” and “sugar” use a similar, though more granular, substrate-structured approach).14 These substrate categories largely map onto the processes anyway, as vegetables and dairy are generally processed by lactic acid fermentation, soy by alkaline fermentation, and vinegar exclusively by acetic acid fermentation. This article will follow the substrate categorization (though terms like “brine” will be referred to as “vegetables” and “sugar” as “drinks”), as although the range of ferments is diverse in origin and ingredients, the methods are often relatively similar within each group—for example, tepache (from Mexico) and piwo jałowcowe (from Poland) both being drinks commonly made by adding sugars and flavorings to water and allowing them to steep together, before straining out the flavorings and bottling. For reference, all living ferments referenced have been ordered by their substrate, also noting fermentation type and origin (where known; Table 1).

With more than 3,500 fermented foods being described by Geoffrey Campbell-Platt, it would be impossible to cover all of them here, but the intention is to give an overview of the most prominent and discussed ferments and to highlight recent research.15

Table 1. Living Ferments

Common Name(s)

Origin

Substrate(s)

Fermentation Type

Kimchi

Korea

Vegetable (Napa cabbage)

Lactic acid

Sauerkraut

Germany

Vegetable (Cabbage)

Lactic acid

Pao cai

China

Vegetable (various)

Lactic acid

Suan cai

China

Vegetable (Napa cabbage/Chinese mustard)

Lactic acid

Gundruk

Nepal

Vegetable (Mustard/radish plant leaves)

Lactic acid

Sinki

Nepal

Vegetable (Mustard plant root)

Lactic acid

Khalpi

Nepal

Vegetable (Cucumber)

Lactic acid

Curtido

El Salvador

Vegetable (Cabbage)

Lactic acid

Agbelima

Ivory Coast/Ghana

Vegetable (Cassava)

Lactic acid

Fufu

West Africa

Vegetable (Cassava)

Lactic acid

Lafun

West Africa

Vegetable (Cassava)

Lactic acid

Attiéké

Ivory Coast

Vegetable (Cassava)

Lactic acid

Gari/garri

West and Central Africa

Vegetable (Cassava)

Lactic acid

Tepache

Mexico

Drink (Sugar/pineapple/fruit)

Lactic acid/Acetic acid

Juniper beer/Piwo jałowcowe

Poland

Drink (Sugar/juniper)

Lactic acid/Acetic acid

Ginger beer

England

Drink (Sugar/ginger)

Lactic acid/Acetic acid

Water kefir/tibicos

Unknown (possibly Mexico)

Drink (Sugar/fruit)

Lactic acid/Acetic acid

Tejuino

Mexico

Drink (Sugar/maize)

Lactic acid/Acetic acid

Atole agrio

Mexico

Drink (Maize)

Lactic acid/Acetic acid

Kombucha

Unknown

Drink (Sugar/tea)

Lactic acid/Acetic acid

Kvass

Russia

Drink (Sugar/rye bread)

Lactic acid/Acetic acid

Amasi

South Africa

Milk

Lactic acid/Acetic acid

Yogurt

Unknown

Milk

Lactic acid

Tätmjölk

Sweden

Milk

Lactic acid

Kefir

North Caucasus

Milk

Lactic acid

Dahi

India

Milk

Lactic acid

Madila

Botswana

Milk

Lactic acid

Lben/leben

East Central and North Africa

Milk

Lactic acid

Soy sauce/shoyu

China/Japan

Soybean

Lactic acid/Aspergillus

Douchi

China

Soybean

Alkaline/Aspergillus

Miso

Japan

Soybean

Alkaline/Aspergillus

Tempeh

Japan

Soybean

Alkaline/Rhizopus

Natto

Japan

Soybean

Alkaline/Bacillus

Thua nao

Thailand

Soybean

Alkaline/Bacillus

Kinema

India

Soybean

Alkaline/Bacillus

Cheonggukjang

Korea

Soybean

Alkaline/Bacillus

Gochujang

Korea

Chili/soybean

Bacillus

Doubanjiang

Korea

Broad bean

Aspergillus/bacillus

Koji

China/Japan

Soybean

Aspergillus

Meju

Korea

Soybean

Aspergillus/bacillus

Source: Table generated by the author.

Fermented Vegetables

Vegetables account for an enormous amount of fermented food. The majority are lacto-fermented, and for these, the essential method is typically the same—salt is added to vegetables (typically at a ratio of 2 to 5 percent of the weight of vegetables), they are placed in a container, and they are then weighed down to keep them submerged under brine (either added as salted water or created after salting the dry vegetables as they exude water). Then the container is sealed until fermentation is complete.16 Vegetable ferments are very commonly spontaneously (or “wild”) fermented, meaning the microbes required to begin lactic acid fermentation are naturally present on the vegetables, and, thus, no starter culture is added.

The most ubiquitous and recognizable vegetable ferments are sauerkraut and kimchi. Each of these ferments are emblematic of the cuisines of their home countries—in Germany, sauerkraut was eaten “three to four times a day” since at least the end of the Middle Ages, according to surgeon and polymath Walter Ryff.17 The origins of sauerkraut have not been extensively studied, and though a prevailing theory mentions China as a possible source,18 spread to Europe by the mid-13th-century Mongol invasion, the evidence is acknowledged by Pederson as “meager.” Similarly, using textual referencing we can trace kimchi back to a 13th-century poem by Korean scholar Yi Gyubo, who refers to radish as “Pickled in jang, perfect for summer / Pickled using salt, ideal for long winter,” which, in the former case, likely means a soy pickle but in the latter a type of dongchimi (radish kimchi), according to Ilgwon Kim.19 In both cases, it is very likely the ferments had long been in regular use before they appeared in literature. The issue, of course, with tracing food origins by earliest mention is that their names can be inconstant, and this is a particular issue in the case of kimchi, as it refers to a group of different vegetable ferments rather than a single dish.20

Most varieties of sauerkraut conform to simplicity, being made with only cabbage and salt, though, occasionally, juniper berries or caraway seeds are added. Behind these elementary ingredients hides the potential for substantial disparity though. As Satora et al. demonstrated, different cultivars of cabbage vary substantially in sugars, and the consequent sauerkraut in chemical characteristics such as lactic acid (which doubles between cultivars) and volatile compounds, as well sensorially in pungency and perceived sourness (though this interestingly does not correlate directly to actual acidity, as other compounds have an influence).21 Despite this, the microbial community of sauerkraut, though somewhat variable due to being spontaneously fermented, is rapidly established and similar to other lacto-ferments, with Leuconostoc and Lactobacillus species dominating.22

Kimchi, by contrast, varies enormously in ingredients. There are over 200 different recognized types, ranging from stuffed eggplant to cabbage with dried persimmon, though the most widely recognized is Chinese leaf or napa cabbage (baechu) kimchi, made with chili flakes (gochugaru), preserved fermented fish (jeotgal), garlic, ginger, and spring onion.23 In tandem with the diversity of types of kimchi, one mini-review highlights the microbial heterogeneity of the ferment.24 Incorporating novel multiomics approaches (genomics, metagenomics, metabolomics), scholars now have a much more comprehensive understanding of the many microbes involved in kimchi and responsible for the resultant taste, quality, and potential health benefits. Working at the World Institute of Kimchi, Se Lee and colleagues have also developed an Omics Database of Fermentative Microbes, which is freely accessible online. Hye Song and their coauthors went on to explore the relationships between the various fermentative microbes indigenous to the raw ingredients of kimchi and the assemblage of the final microbial community.25 They did this by selectively sterilizing four primary ingredients (Chinese leaf cabbage, garlic, ginger, and red pepper). They discovered that the Chinese leaf and garlic were the sources of fermentation—this confirmed earlier research that showed that garlic was plentiful in major lactic acid bacteria for early stage fermentation.26

Looking at other vegetable lacto-ferments, Sichuanese pao cai (or paocai) is a Chinese vegetable pickle similarly made with cabbage (and other firm vegetables such as green beans, carrots, and daikon radish) flavored with chili, garlic, ginger, and Sichuan pepper. Research into pao cai has enumerated the microbial communities typically found in it (and compared them to two other traditional Chinese lacto-ferments—Jiangxi yancai and Dongbei suancai).27 It is commonly seen as quite different from kimchi—typically having a higher salt concentration of 6 to 8 percent w/w,28 though pao cai from provinces other than Sichuan, such as Guizhou and Yunnan, are typically much less salty.29 In fact, it has been shown that that the yeast Pichia is inhibited at higher salinities, which is advantageous, as it otherwise negatively impacts texture.30 However, China has previously asserted that kimchi is pao cai (as the term literally means “pickled vegetables”), which, as Eunju Hwang and Jin Suk Park have explored, has escalated a “kimchi war” between the two countries.31 They describe the cultural dispute as fueled by a series of incidents. With reports from the International Trade Centre’s TradeMap stating that 98 percent of kimchi consumed in Korea in 2014 was imported from China (where it is cheaper), they argue that there was an identity conflict, resulting in the Korean government legislating that restaurants should declare the origin of their ingredients. This feud was furthered when China registered pao cai through the International Organization for Standardization in 2020, and Chinese media reported that kimchi was within scope of this definition (though the ISO standard specifically asserts that “this document does not apply to kimchi”). Hwang and Park argue this follows Foucault’s systems of exclusion by recognition of China as the “authentic” home of kimchi. They go on to show that this was not the first foreign claim on kimchi—Japan proposed “kimuchi” as an official food for the 1996 Olympics and 1998 World Cup, and the Korean government responded by listing kimchi on the United Nations’ Codex Alimentarius in 1996 and opening a number of kimchi museums and the World Institute of Kimchi in 2010. This co-option of fermented foods to “actively appropriate cultures and invent traditions” on a national scale can be used to “create national unity” and lead to “economic benefits through tourism and nation branding.”32

There are key stages which are common to the techniques for making many diverse vegetable lacto-ferments, as they encourage the desired microbes to take hold, while excluding others. The addition of salt is one of the factors which helps to create a “selective environment” which precludes any pathogenic bacteria from taking hold,33 as while many microbes cannot survive in saline conditions, lactic acid bacteria (LAB) are halotolerant and thus have reduced competition for resources in such an environment.34 The presence of salt also pulls water and sugars from vegetables, which pushes out any air pockets in the fermenting vessel and thus reduces oxygen. The limitation of oxygen within the fermenting environment is another feature contributing to the creation of a selective environment favoring the growth of LAB. Many species of LAB are anaerobic or facultatively anaerobic (able to survive in the absence of oxygen). Thus, by submerging vegetables in liquid, species such as Leuconostoc mesenteroides and Lactobacillus plantarum (two of the most common fermentative bacteria in sauerkraut and kimchi) are selected for, and other microbes (such as pathogens) are excluded. Furthermore, as fermentation progresses, the LAB reduce the potential hydrogen (pH) of the ferment, and since they can tolerate acidic conditions, they are able to outcompete non-desirable bacteria which cannot. All of this means that “over the first 48 hours of fermentation, the microbial community of sauerkraut experienced a precipitous drop in the number of bacterial taxa present, likely due to the strong selective pressures of high salinity and acidity in the fermentation environment.”35 Similarly, the microbiome of kimchi becomes far less diverse than that of its ingredients as it ferments. Baechu kimchi adapted to overseas markets is often vegan, and as Zabat et al. discovered, even though the substitution of fish products for miso as a fermented ingredient results in a lower initial microbial diversity, by the end of fermentation, microbial diversities are similar (and similarly low—as the desirable fermentative microbes outcompete others) in both.36

Some select vegetable ferments are made without salt, including Himalayan gundruk, sinki, and khalpi. Gundruk is composed of the leaves of mustard, radish, and other vegetables, which are shredded, wilted, and pressed into an airtight container and then left to spontaneously ferment before being sun dried. Sinki is made similarly, using the taproots (rather than leaves) of the mustard plant, and for khalpi, the process is followed using cucumber. All three of these ferments have broadly similar LAB microbial communities to other lacto-ferments.37

Cassava lacto-ferments are a major group and staple within many African foodways, including agbelima, fufu, lafun, attiéké, and gari. However, they are routinely cooked as part of preparation, as cassava can otherwise be cyanogenic (though it has been noted that fermentation can reduce cyanide content.38 As they are not “living ferments,” they are out of scope for this article, but they have been the subject of limited study so far.39

Nonalcoholic and Low-Alcohol Fermented Drinks

Clearly, the most prevalent of all fermented drinks are alcoholic, yet as the appetite for alcohol alternatives increases, fermentation can readily provide these too. As the International Wines and Spirits Record (UK) commented in their research, “the market value [across ten key markets] of no/low-alcohol products in 2022 surpassed $11 billion, up from $8 billion in 2018.” There are a great many nonalcoholic and low-alcohol fermented drinks (NLAFDs) from an array of food cultures, ranging from fermented fruit juices to tea, cereals, and, occasionally, vegetables. Historically, they have been valued for their nourishment, as well as their ability to provide food security by preserving ingredients.40 Their methods of production are varied, and while many fermented drinks employ a starter culture (such as ginger beer or water kefir), others are spontaneously or “wild” fermented (such as tepache and sometimes kvass). The reason for the propensity toward using starters is likely to counterbalance the removal of salt from the “selective environment” arsenal (as salty drinks are neither typically palatable nor renally salutary), and so, alongside dairy, NLAFDs can broadly be contrasted with vegetable and soybean ferments in this regard.

Kombucha is one of the most popular fermented drinks in the world, with the global market estimated to reach $3.5 to 5 billion by 2025.41 It is made by adding a symbiotic culture of bacteria and yeasts (or SCOBY) to cooled, sweetened tea and allowing it to ferment aerobically for seven to ten days before removing the SCOBY, optionally adding flavorings and bottling for a shorter period of secondary fermentation to allow for carbonation.42 Acetic acid bacteria (AAB) and yeasts are the most common microbes in kombucha, and though they note that no specific species of yeast is characteristic, they observe that Brettanomyces seem particularly well-suited to the substrate, though Komagataeibacter xylinus is most characteristic, as it is likely responsible for the production of the iconic cellulose pellicle (often colloquially referred to as the SCOBY, though, in fact, it is only an expression of it). They go on to explore the health benefits consequent to this microbial community, noting that “the probiotic potential of kombucha seems to be rather limited, as the consumption of living yeast or AAB cells is not commonly associated with health benefits.”43 Countering this, however, Swastik Sen and Thomas Mansell point out that the yeast Saccharomyces boulardii (a strain of Saccharomyces cerevisiae which has been used therapeutically since the 1980s) “has been shown to be useful in fighting various GI tract infections in rat models as well as human beings.”44 However, in the specific case of kombucha, Julie Kapp conducted a thorough meta-analysis of 310 articles on the beverage to investigate empirical health benefits in human subjects and did not find any controlled studies, though one uncontrolled study did show that regular kombucha consumption was associated with normalized blood sugar in type 2 diabetes patients.45 Another (though less extensive) review has come to similar conclusions regarding the ongoing need for human clinical trials to ascertain health benefits.46

Mexico is home to a great many fermented drinks, and they form an important part of the country’s culinary identity, but few of them have been written about extensively. There are over 200 fermented foods and drinks in the country, but only twelve of them have been studied (and where they have been, the literature is often only available in Spanish).47 Looking at some of the NLAFDs within Mexican foodways, there is tepache, tuba fresca, atole agrio, pozol, and tejuino. César Ojeda-Linares and colleagues have conducted a thorough review of these and many other drinks (termed “traditional Mexican fermented beverages” or TMFBs), in which they identified that research is lacking. They note that in particular, further study is needed into the cultural and technological aspects of Mexico’s intangible biocultural heritage. They observe that TMFBs knowledge and production methods are particularly fragile as they are often communicated indirectly, as they are “embedded as part of the daily lives of many people, including those currently marginalized rural or Indigenous groups” and that the paucity of research has left an “outstanding reservoir of genetic resources” hidden within these TMFBs as an untapped resource for secondary products.48

One of the more studied drinks is tepache. Though the name derives from the Náhuatl word tepitl, meaning “corn drink,” it is very commonly now made with fruit.49 Depending on the region it may include apple, orange, or guava. Typically, however, it is made using pineapple peel fermented with piloncillo sugar, water, and, occasionally, a starter culture—though typically, it is left to spontaneously ferment in a wooden cask called a tepachera. One in vitro study discovered that “three yeasts were able to survive under conditions that simulate the gastrointestinal tract . . . [and] can be considered as microorganisms with probiotic potential.”50 One of these yeasts had not been previously reported in tepache, demonstrating the potential for further study in this vein. Tepache is also conspicuous as a ferment made using food by-products, which is an area where fermentation holds further potential. Another study explored the potential of new beverages using food waste, such as kvass made from rye and oat flour combined with apple, carrot, and pumpkin by-product flour, and consider issues such as standardization of raw materials and production process optimization. However, tepache shows that traditional fermented drinks can be not only an inspiration but provide ready-made solutions.51

Kati Väkeväinen et al. have investigated atole agrio—a drink with variable production methods using short (hours rather than days) spontaneous fermentation with the maize in either liquid or solid state. They identified and characterized the LAB microbiota and evaluated the species to explore if any could be used as starters to standardize and streamline production, electing six strains for future study in this regard.52

Tejuino is another maize-based fermented drink that has been reviewed.53 The drink has ceremonial use in the ethnic groups of Tepehuanes, Yaquis, Pimas, Tarahumaras, and Huichol, and its production descended from that of an alcoholic drink—tesgüino. The authors observed that, according to Huichol custom, it must be made only by women who are separated from men and have not washed their hands with soap, which could infer than the skin microbiome is intuited as a source for microbes, though this is not discussed. When made commercially, the maize is nixtamalized instead of being germinated, and fermentation lasts only twelve to twenty-four hours. The authors highlight other studies that have reported that the germination of maize and fermentation process in traditional (as opposed to commercial) tejuino could increase its nutritional value, as well as flavor.54

Conservation efforts to revive traditional no/low-alcohol drinks can bear fruit, as Tomasz Madej et al. describe in Poland.55 Juniper beer (piwo jałowcowe) was a common fermented drink in much of northern Poland until the beginning of the 20th century,56 when reports of its consumption began to decline (and continued to do so until a revival of the tradition in the Kurpie region). The Kurpie people were once relatively isolated forest dwellers and made use of fermentation to process a number of wild plant species for food, including fermented lime tree leaf bud soup and lacto-fermented birch sap. Juniper was a prominent plant (Adam Chętnik dedicates an article to it in his study of the Kurpie) and among many uses, was fermented with sugar or honey and water to make a nonalcoholic drink. From anthropological interviews, “revival of the beer can likely be traced to one folklore event, designed for tourists in the 1990s when one of our respondents made the beverage . . . [and] noticed that the beer was received favorably by tourists.”57

Fermented Dairy

Due to its short shelf life, dairy is a good candidate for fermentation as a means of preservation, and, thus, fermented dairy has had a long history among milk-drinking societies. Fermentation also has a particular additional benefit in the context of dairy, as it can drastically reduce the lactose content of milk (by converting it to lactic acid). This is useful because many populations cannot digest lactose, and, until sometime around 10,000 years ago, no one could process it beyond infancy.58 Rosenstock, Ebert, and Scheibner note that until the genetic emergence of lactase persistence, dairy would most likely have been consumed in a fermented state (or it would have been an intestinally uncomfortable experience) and, therefore, the ability to ferment milk would likely have been discovered around the same time as animal milk use was adopted (thought to be around 9000–6500 BCE). They acknowledge it is difficult to find concrete evidence for this dating though, even with access to a range of data on prehistoric milk and dairy consumption, including protein analysis on calcified dental plaque and ceramic vessels. They argue that in order to more precisely understand prehistoric fermentation, a new approach of “ethno- and archaeo-microbiology” is needed to isolate and examine (for example) any remnant starter culture on pottery shards for “ancient biomolecules.”59

By far the most ubiquitous form of fermented dairy is yogurt. Although the name is Turkish in origin (from the root yoğ, meaning “thicken”), it is only recorded as far back as 1070, when it is mentioned twice in medieval Turkish literature.60 Yogurt is predated though by a number of other, similar-sounding foods such as oxygala, an ancient Greek fermented dairy product, and dahi, also referred to as “curd,” from the Indian subcontinent.61 This soured milk is first described in the sacred Hindu text, the Rigveda, placing its origins in the Vedic era (1500–600 BC). The method recounted there is to either use backslopping (retaining a portion of a previous batch as a starter culture) or by adding vegetal matter, such as “greens from the putika creeper, the bark from palasha plant or the fruit of the kuvala,” suggesting that these plants were sources of microbes necessary for fermenting milk.62 Similarly, tätmjölk—a thick fermented milk drink found in Scandinavia—is usually made using a starter culture, but can also be made by immersing leaves of the butterwort plant (Pinguicula vulgaris) in milk. This process has been recorded since the 18th century.63 This assertion is supported by other analyses, such as pulsed-field gel electrophoresis which indicated a plant-associated origin for dairy starter strains.64 This transference has parallels in other ferments, such as tempeh (as discussed in the section on fermented soybeans).

Yogurt has a long history through the Levant and Eastern Europe but only became popular in Western Europe after the Russian immunologist Élie Metchnikoff began researching it at the Pasteur Institute in the early 20th century and was impressed by “the number of centenarians to be found in Bulgaria,”65 after reading the work of Stamen Grigorov (who had recently discovered one of the primary bacterial strains for fermenting yogurt, and naming it Lactobacillus bulgaricus after his home country). By suggesting that yogurt could stave off aging by repopulating the intestines with certain bacteria, he propelled it to immense popularity. As Luba Vikhanski remarks in her biography, “the modern yogurt industry was arguably born in the lecture hall of the Society of French Agriculturalists in Paris on June 8, 1904 [when Metchnikoff delivered a lecture on old age, which he described as a disease which could be countered by yogurt].”66

Perin Gurel notes that, in order to construct an exotic yet palatably white image for yogurt, the Turkish migrant founder of US brand Chobani was among the first to market strained yogurt as “Greek.”67 She argues that its salutary fetishization as a health food has also isolated yogurt from its origins: “in the case of yogurt’s popularization in the United States, feminization as a ‘diet’ food has been a significant part of its cultural neutering.”68 She draws on Najla Said’s memoirs to illustrate the sharp contrast between the “gentle femininity” of the sweetened, fruit-augmented, single-serving yogurt Najla’s American high school classmates eat, with the large tubs of “plain” yogurt her Palestinian-Lebanese family cook with at home. The amount of added sugar in sweetened yogurts can be as high as seventeen grams per hundred grams, with only two out of 101 children’s yogurt products surveyed being categorized as low sugar (less than five grams per hundred grams), as a British Medical Journal report noted.69 Analyzing newspaper and magazine references 1990 to 2012, Gurel finds that “low-fat” is overwhelmingly the most popular adjective associated with yogurt, occurring over twenty-eight times more regularly than the next, “Greek-style.” The shift in nutritional focus in the marketing of yogurt from a food to prolong life to one that helps with weight loss is, of course, decidedly gendered and particularly incongruous with the modern Turkish depictions that Gurel references of yogurt in advertising as something that families eat together and which men need to provide.70

This adaptation of fermented dairy to local markets isn’t unique to yogurt—in the case of kefir, Muir, Tamime, and Wszołek found from their research comparing “traditional” (cultured with SCOBY grains) with “modified” (cultured using a defined blend of microorganisms and lightly carbonated) kefir, they found that the latter was “likely to be more acceptable to the consumer in Western Europe.”71 One review ascribes to kefir “a myriad of bioactive properties to include anticancer, antimicrobial, anti-inflammatory, hypocholesterolemic, wound healing, antioxidant and gastrointestinal aiding properties” but acknowledges that these effects have largely only been observed in vitro and “need to be substantiated by studies in animals and humans.”72 Looking more broadly at health benefits, yogurt and other fermented milk products are among the most thoroughly explored ferments, with one article finding “decades of research [suggesting] that consumption of . . . fermented milk products is associated with improved health outcomes.”73 They highlight evidence for a reduced risk of breast and colorectal cancer and type 2 diabetes, improved weight maintenance, and improved cardiovascular, bone, and gastrointestinal health, as well as improved lactose digestion and a reduction in symptoms of lactose intolerance.

Some research has been carried out on the South African fermented milk drink amasi, which is summarized in a review.74 It is traditionally fermented in a calabash, which is posited as the microbial carrier which inoculates fresh batches. It is unusual among fermented milk products in that the authors highlight a lack of research into its health benefits. A more wide-ranging review into African fermented dairy products (AFDPs) highlights twenty-three other examples from across the continent, which they categorize as predominantly yogurt or yogurt-like, spontaneously fermented, and made at a domestic level (excepting amasi and Botswanan madila).75 The authors acknowledge that some of the products bear regional generic names for “fermented milk product” (such as lben in Algeria and leben across North Africa) and thus may not in fact be distinct. Helpfully, they categorize the AFDPs by production methods and collate their documented microbial communities. There is significant scope for further study of these products to better establish their history, microbial community, and potential health benefits.

Fermented Soybeans

Soybeans are a very common substrate for fermentation across East and Southeast Asia, responsible for ferments as diverse as soy sauce and tempeh. Although soybeans are one of the most heavily farmed crops in the world, they contain trypsin inhibitors, which render them indigestible by humans unless processed—and fermentation can reduce these by 89 to 99 percent.76

The earliest soy ferment was likely salted, fermented soy beans (douchi or shih)—this is suggested by Hsing-Tsung Huang in his brilliant and comprehensive exploration of fermentation in China.77 On the basis of first references appearing in ancient literature, he posits that it was developed between the end of the Qin dynasty (209 BC) and late Western Han (a period ending in 9 AD). His assertion is supported by archaeological evidence from the Mawangdui tomb site, where douchi were found buried with the body of the noblewoman Xin Zhui.78

Many Japanese soy-based ferments (including douchi, soy sauce, and miso) are created with the fungus Aspergillus oryzae—both the fungus itself and A. oryzae-cultured soybean substrate are referred to within Japanese food culture as koji (though koji can contain other microbes). Koji is able to produce the enzymes amylase and protease which break down proteins and starches, respectively, into sugars and amino acids.79 Koji most likely originated in China, where A. oryzae had been used in food and drink production for 2,000 to 3,000 years.80 In China, the filamentous fermentative fungi are generally referred to as jiuqu or qu—a term that encompasses a broader range of fermentations involving a greater diversity of substrates and microbial species, and a similar starter called meju is used for many foods and drinks in Korea.81

Tempeh is an Indonesian ferment that takes the form of a solid cake. It is unique in that, as Huang asserts, it is the “only major processed soyfood that did not originate in China or Japan.”82 The first mention of it is noted by Shurtleff and Aoyagi as being in the Javanese text Serat Centhini, which was published in 1815 but documents the 17th century.83 One study also cites evidence of 18th-century tempeh consumption but asserts that it is regarded as a “low social value food” and thus one could suppose that its inclusion in the literature may have been prejudiced against it.84 However, it has taken on a new image as “a global emergence of initiatives to rebrand tempeh as an affordable, sustainable, and healthy plant-based product.”85

The theory that tempeh was developed entirely independently of imported koji or qu raises the question of the origins of the Rhizopus oryzae culture needed to ferment it. Ogawa et al. hypothesize that they may have come from hibiscus leaves, on the basis that, in small-scale production, these leaves are used to transfer the desired mold from finished tempeh to new batches—their analysis found that 95 percent of Hibiscus tiliaceus samples did indeed include R. oryzae, confirming the plant as a possible progenitor for the tempeh mold.86

Looking further beyond A. oryzae, many ferments are also made using Bacillus species. The best-known are Japanese natto, Thai thua nao, Indian kinema, and Korean cheonggukjang. All of these ferments, while varying in production method, are similarly alkaline, sticky, and formed of whole soybeans, and thus Tamang proposes that they can be arranged into a “Kinema-Natto-Thua nao triangle” (or “KNT-triangle”).87 They observe that while analogous ferments exist in Cambodia, Laos, Vietnam, Myanmar, southern China, and northeast India, there are none observed outside of the “KNT-triangle.” Furthermore, while ascertaining whether kinema or another of these ferments came first is unknown, it is likely that the origin was somewhere within this triangle. Tamang is also an excellent source for other Himalayan ferments, investigating gundruk, sinki, goyang, and many others, as noted in the fermented vegetables section.88 Not all Bacillus soybeans ferments are slimy and alkaline, however—the Korean dried fermented soybean starter meju is somewhat similar to koji but spontaneously fermented instead of inoculated. It is used to create ganjang (Korean soy sauce), doenjang (similar to miso paste), and the chili paste gochujang89— Seo-Jung Jang et al. showed that 96 percent of gochujang’s bacterial community is typically Bacillus.90

Mary Astuti et al. note that tempeh takes many forms in Indonesia other than soybean, including sword beans, velvet beans, and pigeon peas.91 Similarly, in both China and Japan, A. oryzae (as well as other associated filamentous fungi, such as R. oryzae) is used on a number of other substrates apart from soybean, such as rice (to make products such as amazake, sake, shōchū, huangjiu, and rice vinegars) and broad beans (doubanjiang).

In 1884, Japanese chemist Jokichi Takamine took koji to America and adapted its fermentation process for whisky manufacturing, extracting amylase enzymes from bran by growing the fungi on it.92 This realization that koji could be faster and cheaper than the traditional malting process at creating enzymes to break down starch was revelatory, and Takamine’s discovery has been described as “where East meets West in fermenting technology.”93

This use of novel substrates has expanded rapidly through the 2010s, and chief among the champions of miso innovation is the work of the restauratnt noma in Copenhagen. Regarding the extensive fermenting experimentation that noma founder Rene Redzepi and David Zilber (head of noma’s fermentation lab) carried out to “construct a flavor that could define our restaurant and possibly our entire region,” they declare that “[the] Nordic version of miso is perhaps the most successful attempt.94 Their best-known iteration is yellow pea miso, or “peaso,” but they demonstrated that miso can be made with everything from rye bread to hazelnuts. The noma team carried out many other experiments with miso, including Joshua Evans’s work comparing the microbial ecology of various misos made in Copenhagen with those made similarly in Tokyo to investigate the concept of a geographical terroir—he found that the method mattered more than the location.95 This reflects the extensive review into sourdough bread cultures, which found that the “immediate environment, such as local air quality and other products being stored [nearby]” had more of an impact than the wider location.96 Similar findings have also been demonstrated in lacto-ferments, in a study comparing kimchi produced in Italy with that from Korea, which found “microbial populations and dynamics that greatly overlapped.”97 Evans’s work is also corroborated by Rei Peraza and Gabriel G. Perron, who employed a DNA-sequencing approach to study a number of lacto-ferments created in their lab (including jalapeño, radish, and pine needles) and found that “each fermented food group harbored microbial communities similar to those previously described in the literature” (though they also noted that ferments made with foraged ingredients such as pine needles had the most microbial diversity).98

The Future

There is substantial further research to be done into fermentation, across many fields. The most promising of these are health, nutrition, innovation, and novel products, though there is also great potential for further ethnobiological, anthropological, and historical work, especially on the ferments of Africa and Latin America. As has been shown in the case of Mexico’s fermented food landscape, the limited research has illuminated the benefits of further study.99

While there are a large number of fermented foods and drinks that vary in their techniques, ingredients, and microbial communities, one can draw broad parallels among them by substrate. These categories also often indicate the reason that they were traditionally fermented, whether it be to increase durability (in the case of dairy) or reduce toxicity (in the case of soy). However, they are often sought out for a singular reason—health benefits. With this in mind, it is critical that more research is done to better understand the complexities of the human microbiome and how fermented food interacts with it. Historically, many of the posited benefits of fermented food have been based on in vitro studies, which are good indicators but not sufficient in themselves. However, excellent human trials are emerging, such as one study that showed that increased consumption of fermented foods lead to decreases in inflammatory markers and increases in gut microbiota diversity. The study showed though, that of the new microbes found in the subjects, only a small percentage (~5 percent) were in common with those found in the fermented foods consumed, leading to the question as to where the new microbes originated.100

There is also ample opportunity to further explore the utility of fermentation for creating novel foods, especially at targeting problems such as sustainability. With the fruit and vegetable sector creating the largest proportion of food waste, and the attendant environmental and economic issues that it brings, the potential to cycle these byproducts back into the food chain using fermentation is enormous, and some restaurants (such as Silo in London) are beginning to harness this.101

Ferments also have the capability to teach us about complex communities—the microbial interactions in sauerkraut, cheese rinds, and kombucha take place in reproducible, manipulable communities with “tractable complexity,” which are simple enough to be understood yet elaborate enough to be “biologically interesting.” This makes them excellent candidates to act as a model for understanding other, more intricate microbial systems, such as those in the human body.102

The origins of fermentation and the way in which it has co-evolved with humanity still bears further exploration. Humans have steered the evolution of many fermentative microbes, nurturing them and transferring them to radically new environments (such as from plants to dairy). As Erik Hom and Alexandra Penn observe,“many culturally codified practices evolved to reliably produce fermented products,” such as songs and dances to precisely time certain processes and specifically constructed niches built to coddle microbes (and those environments may themselves become reservoirs for inocula).103 This domestication leads to the question of whether we are ourselves being shaped by the microbes. They have apparently caused in us physiological changes on an evolutionary scale, as well as behavioral changes on a cultural scale, and with further understanding of their influence on our gut microbiome, researchers will hopefully be able to establish the causative links that fermented food consumption has on individual bodies.104

Further Reading

  • Bryant, Katherine L., Christi Hansen, and Erin E. Hecht. “Fermentation Technology as a Driver of Human Brain Expansion.” Communications Biology 6, no. 1 (2023): 1190.
  • Brice, Jeremy. “Killing in More-than-Human Spaces: Pasteurisation, Fungi, and the Metabolic Lives of Wine.” Environmental Humanities 4, no. 1 (2014): 171–194.
  • El-Sayed, Sara, and Christy Spackman. “Follow the Ferments.” Gastronomica 22, no. 1 (2022): 20–33.
  • Hui, Y. H. Handbook of Food and Beverage Fermentation Technology. New York: Marcel Dekker, 2004.
  • Katz, Sandor Ellix. Wild Fermentation: The Flavor, Nutrition, and Craft of Live-Culture Foods. White River Junction, VT: Chelsea Green Publishing, 2016.
  • Kim, Kwangok. Humanistic Understanding of Kimchi and Kimjang Culture. Gwangju: World Institute of Kimchi, 2014.
  • Morrow, Oona. “Ball Jars, Bacteria, and Labor: Co-Producing Nature through Cooperative Enterprise.” Food and Foodways 29, no. 3 (2021): 264–280.
  • “No- and Low-Alcohol Category Value Surpasses $11bn in 2022.” IWSR. 2022.
  • Owens, J. D., ed. Indigenous Fermented Foods of Southeast Asia. Boca Raton, FL: CRC Press, 2014.
  • Satora, Paweł. “Yeast Microbiota during Sauerkraut Fermentation and Its Characteristics.” International Journal of Molecular Sciences 21, no. 24 (2020): 9699.
  • Shurtleff, William, and Akiko Aoyagi. History of Tempeh and Tempeh Products (1815–2020): Extensively Annotated Bibliography and Sourcebook. Lafayette, CA: Soyinfo Center, 2020.
  • Tamang, Jyoti P., ed. Ethnic Fermented Foods and Alcoholic Beverages of Asia. New Delhi: Springer India, 2016.
  • Xiao, Muyan, et al. “Correlation between microbiota and flavours in fermentation of Chinese Sichuan Paocai.” Food Research International 114 (2018): 123–132.
  • Zabat, Michelle A., et al. “The Impact of Vegan Production on the Kimchi Microbiome.” Food Microbiology 74 (2018): 171–178.

Notes

  • 1. Li Liu et al., “Fermented Beverage and Food Storage in 13,000 Year-Old Stone Mortars at Raqefet Cave, Israel: Investigating Natufian Ritual Feasting,” Journal of Archaeological Science: Reports 21 (2018): 783–793.

  • 2. Adam Boethius, “Something Rotten in Scandinavia: The World’s Earliest Evidence of Fermentation,” Journal of Archaeological Science 66 (2016): 169–180.

  • 3. Mélanie Salque et al., “Earliest Evidence for Cheese Making in the Sixth Millennium BC in Northern Europe,” Nature 493, no. 7433 (2013): 522–525.

  • 4. Matthew A. Carrigan et al., “Hominids Adapted to Metabolize Ethanol Long before Human-Directed Fermentation,” Proceedings of the National Academy of Sciences of the USA 112, no. 2 (2015): 458–463.

  • 5. Anna Peters et al., “Metabolites of Lactic Acid Bacteria Present in Fermented Foods Are Highly Potent Agonists of Human Hydroxycarboxylic Acid Receptor 3,” PLoS Genetics 15, no. 5 (2019): e1008145.

  • 6. Carrigan et al. “Hominids Adapted to Metabolize Ethanol.”

  • 7. Katherine R. Amato, Elizabeth K. Mallott, Paula D’Almeida Maia, and Maria Luisa Savo Sardaro, 2021, “Predigestion as an Evolutionary Impetus for Human Use of Fermented Food,” Current Anthropology 62, no. S24, (October 2021): S207–S219.

  • 8. Eva Rosenstock, Julia Ebert, and Alisa Scheibner, “Cultured Milk Fermented Dairy Foods along the Southwest Asian–European Neolithic Trajectory,” Current Anthropology 62, no. S24 (2021): S269.

  • 9. Keith H. Steinkraus, “Classification of Fermented Foods: Worldwide Review of Household Fermentation Techniques,” Food Control 8, no. 5–6 (1997): 311–317.

  • 10. Soichi Furukawa, Taisuke Watanabe, Hirohide Toyama, and Yasushi Morinaga, “Significance of Microbial Symbiotic Coexistence in Traditional Fermentation,” Journal of Bioscience and Bioengineering 116, no. 5 (2013): 533–539; and Anna Y. Alekseeva, Anneloes E. Groenenboom, Eddy J. Smid, and Sijmen E. Schoustra, “Eco-Evolutionary Dynamics in Microbial Communities from Spontaneous Fermented Foods,” International Journal of Environmental Research and Public Health 18, no. 9 (2021): 10093.

  • 11. R. J. Clarke, “Green Coffee Processing,” in Coffee: Volume 2: Technology (Dordrecht, The Netherlands: Springer, 2011), 1–34.

  • 12. James Read, Of Cabbages and Kimchi: A Practical Guide to the World of Fermented Food (London: Particular Books, 2023), 12.

  • 13. John Leech et al., “Fermented-Food Metagenomics Reveals Substrate-Associated Differences in Taxonomy and Health-Associated and Antibiotic Resistance Determinants,” mSystems 5, no. 6 (December 2020): e00522-20.

  • 14. Mohamed Mannaa, Gil Han, Young-Su Seo, and Inmyoung Park, “Evolution of Food Fermentation Processes and the Use of Multi-Omics in Deciphering the Roles of the Microbiota,” Foods 10, no. 11 (2021): 2861.

  • 15. Geoffrey Campbell-Platt, Fermented Foods of the World: A Dictionary and Guide (London: Butterworths, 1987).

  • 16. Keith H. Steinkraus, ed., Handbook of Indigenous Fermented Foods (New York: Marcel Dekker, 1995); Mike Battcock and Sue Azam-Ali, Fermented Fruits and Vegetables: A Global Perspective (Rome: Food and Agriculture Organization of the United Nations, 1998); and Julia Skinner, Our Fermented Lives: A History of How Fermented Foods Have Shaped Cultures & Communities (North Adams, MA: Storey Publishing, LLC, 2022).

  • 17. Melitta W. Adamson, ed., Regional Cuisines of Medieval Europe: A Book of Essays (New York, NY: Routledge, 2002), 163.

  • 18. Carl Severin Pederson, Microbiology of Food Fermentations (Westport, CT: AVI, 1971); and Steinkraus, Handbook of Indigenous Fermented Foods.

  • 19. Ilgwon Kim, “Review on Uniqueness of the Origin of Kimchi Based on the Process of Development,” The Humanistic Understanding of Kimchi 2 (2015): 96.

  • 20. Kim, “Review on Uniqueness of the Origin of Kimchi.”

  • 21. Paweł Satora et al., “Chemical Composition and Sensory Quality of Sauerkraut Produced from Different Cabbage Varieties,” LWT 136, no. 1 (2021): 110325.

  • 22. Michelle A. Zabat et al., “Microbial Community Analysis of Sauerkraut Fermentation Reveals a Stable and Rapidly Established Community,” Foods 7, no. 5 (May 2018): 77.

  • 23. Hong S. Cho, “Food and Nationalism: Kimchi and Korean National Identity,” The Korean Journal of International Studies 4, no. 1 (2006); and Michelle A. Zabat et al., “Microbial Community Analysis of Sauerkraut Fermentation Reveals a Stable and Rapidly Established Community,” Foods 7, no. 5 (May 2018): 77.

  • 24. Se H. Lee, Tae W. Whon, Seong W. Roh, and Che O. Jeon, “Unraveling Microbial Fermentation Features in Kimchi: From Classical to Meta-Omics Approaches,” Applied Microbiology and Biotechnology 104, no. 18 (2020): 7731–7744.

  • 25. Hye S. Song et al., “Microbial Niches in Raw Ingredients Determine Microbial Community Assembly during Kimchi Fermentation,” Food Chemistry 318 (2020): 126481.

  • 26. Sae B. Lim et al., “Garlic Is a Source of Major Lactic Acid Bacteria for Early-Stage Fermentation of Cabbage-Kimchi,” Food Science and Biotechnology 24 (2015): 1437–1441.

  • 27. Yangsheng Xiao et al., “The Microbial Communities and Flavour Compounds of Jiangxi Yancai, Sichuan Paocai and Dongbei Suancai: Three Major Types of Traditional Chinese Fermented Vegetables,” LWT—Food Science and Technology 121 (March 2020): 108865.

  • 28. Linjun Jiang Jiang et al., “Metagenomic Study on Chinese Homemade Paocai: The Effects of Raw Materials and Fermentation Periods on the Microbial Ecology and Volatile Components,” Foods 11, no. 1 (December 2021); and Zimeng Zheng et al., “Effects of Assorted Radishes on the Flavor Development and Bacterial Community Succession of Radish Paocai during Fermentation,” LWT 187 (September 2023): 115377.

  • 29. Zhanggen Liu et al., “Comparison of Bacterial Diversity in Traditionally Homemade Paocai and Chinese Spicy Cabbage,” Food Microbiology 83 (2019): 141–149.

  • 30. Ting Mi et al.,. “Effects of Salt Concentration on the Quality and Microbial Diversity of Spontaneously Fermented Radish Paocai,” Food Research International 160 (2022): 111622.

  • 31. Eunju Hwang, and Jin Suk Park, “Nationality of Food: Cultural Politics on the UNESCO List of Intangible Cultural Heritage and Food Museums,” Telos: Critical Theory of the Contemporary 2023, no. 202 (2023): 21–41.

  • 32. Hwang and Park, “Nationality of Food,” 40.

  • 33. Sandor E. Katz, The Art of Fermentation: An In-Depth Exploration of Essential Concepts and Processes from Around the World (White River Junction, VT: Chelsea Green, 2012).

  • 34. Michelle A. Zabat et al., “The Impact of Vegan Production on the Kimchi Microbiome,” Food Microbiology 74 (2018): 171–178.

  • 35. Zabat et al., “Microbial Community Analysis,” 5.

  • 36. Zabat et al., “Impact of Vegan Production,” 171–178.

  • 37. Jyoti P. Tamang, Himalayan Fermented Foods: Microbiology, Nutrition, and Ethnic Values (Boca Raton, FL: CRC Press, 2010), 25–36.

  • 38. Clifford N. Obi, Onyemaechi Okezie, and T. Ukaegbu, “Fermentation Reduces Cyanide Content during the Production of Cassava Flours from Sweet and Bitter Cassava Tuber Varieties,” Asian Food Science Journal 11, no. 1 (2019): 1–10.

  • 39. Oluwafemi A. Adebo et al., eds., Indigenous Fermented Foods for the Tropics (San Diego, CA: Elsevier Science, 2023); and Niguse H. Halake and Bhaskarrao Chinthapalli, “Fermentation of Traditional African Cassava Based Foods: Microorganisms Role in Nutritional and Safety Value,” Journal of Experimental Agriculture International 42, no. 9 (2020): 56–65.

  • 40. Aristea Baschali et al., “Traditional Low-Alcoholic and Non-Alcoholic Fermented Beverages Consumed in European Countries: A Neglected Food Group,” Nutrition Research Reviews 30, no. 1 (2017): 1–24.

  • 41. Patrícia Batista, Maria R. Penas, Manuela Pintado, and Patrícia Oliveira-Silva, “Kombucha: Perceptions and Future Prospects,” Foods 11, no. 3 (2022).

  • 42. Katz, Art of Fermentation.

  • 43. David Laureys, Scott J. Britton, and Jessika De Clippeleer, “Kombucha Tea Fermentation: A Review,” Journal of the American Society of Brewing Chemists 78, no. 3 (2020): 171.

  • 44. Swastik Sen and Thomas J. Mansell, “Yeasts as Probiotics: Mechanisms, Outcomes, and Future Potential,” Fungal Genetics and Biology 137 (2020): 103333.

  • 45. Julie M. Kapp, “Kombucha: A Systematic Review of the Empirical Evidence of Human Health Benefit,” Annals of Epidemiology 30 (February 2019): 66–70.

  • 46. Haruthairat Kitwetcharoen et al., “Kombucha Healthy Drink—Recent Advances in Production, Chemical Composition and Health Benefits,” Fermentation 9, no. 1 (2023): 48.

  • 47. Patricia L. Oliveras, Pía Herrera, and Rubén M. Terrazas, “Poco estudiados, los fermentados indígenas,” Gaceta UNAM 3655 (2003): 12–13.

  • 48. César Ojeda-Linares et al., “Traditional Fermented Beverages of Mexico: A Biocultural Unseen Foodscape,” Foods 10, no. 10 (2021): 2390.

  • 49. Ojeda-Linares et al., “Traditional Fermented Beverages of Mexico.”

  • 50. Haydee E. Romero-Luna, Audry Peredo-Lovillo, and Gloria Dávila-Ortiz, “Tepache: A Pre-Hispanic Fermented Beverage as a Potential Source of Probiotic Yeasts,” in Hispanic Foods: Chemistry of Fermented Foods, ed. Michael Tunick and Elvira Gonzalez de Mejia (Washington, DC: American Chemical Society, 2022), 135–147.

  • 51. Elisabete M. Alexandre, Nuno F. Aguiar, Glenise B. Voss, and Manuela E. Pintado, “Properties of Fermented Beverages from Food Wastes/By-Products,” Beverages 9, no. 2 (2023): 45.

  • 52. Kati Väkeväinen et al., “Characterization of Lactic Acid Bacteria Recovered from Atole Agrio, a Traditional Mexican Fermented Beverage,” LWT - Food Science and Technology 88 (2017): 109–118.

  • 53. Ángel E. Rubio-Castillo et al., “Traditional Non-Distilled Fermented Beverages from Mexico to Based on Maize: An Approach to Tejuino Beverage,” International Journal of Gastronomy and Food Science 23 (2021): 100283.

  • 54. Narpinder Singh, Sandeep Singh, and Khetan Shevkani, “Maize: Composition, Bioactive Constituents, and Unleavened Bread,” in Flour and Breads and Their Fortification in Health and Disease Prevention, ed. Victor R. Preedy, Ronald R. Watson, and Vinood B. Patel (Amsterdam: Elsevier Science, 2011), 88–99; and Pasjanant Hiran, Orapin Kerdchoechuen, and Natta Laohakunjit, “Combined Effects of Fermentation and Germination on Nutritional Compositions, Functional Properties and Volatiles of Maize Seeds,” Journal of Cereal Science 71 (2016): 207–216.

  • 55. Tomasz Madej, Ewa Pirożnikow, Jarosław Dumanowski, and Łukasz Łuczaj, “Juniper Beer in Poland: The Story of the Revival of a Traditional Beverage,” Journal of Ethnobiology 34, no. 1 (2014): 84–103.

  • 56. Adam Chętnik, Pożywienie Kurpiów: jadło i napoje zwykłe, obrzędowe i głodowe (Kraków, Poland: Polish Academy of Arts and Sciences, 1936).

  • 57. Madej et al., “Juniper Beer in Poland,” 93.

  • 58. Laure Ségurel and Céline Bon, “On the Evolution of Lactase Persistence in Humans,” Annual Review of Genomics and Human Genetics 18 18, no. 1 (2017): 297–319.

  • 59. Rosenstock, Ebert, and Scheibner, “Cultured Milk Fermented Dairy Foods,” S269.

  • 60. Fatih Yildiz, ed., Development and Manufacture of Yogurt and Other Functional Dairy Products (Boca Raton, FL: CRC Press, 2010).

  • 61. Jessica Hendy, Matthäus Rest, and Christina Warinner, “The Ancient History of Yoghurt,” in The Book of Fermentology (Raleigh: NC State University Libraries, 2022); and Joan P. Alcock, Food in the Ancient World (Westport, CT: Greenwood Press, 2006).

  • 62. Ramesh C. Chandan and Arun Kilara, eds., Manufacturing Yogurt and Fermented Milks (Oxford: Wiley, 2013), 395.

  • 63. Rangne Fondén, Kaarle Leporanta, and U. Svensson, “Nordic/Scandinavian Fermented Milk Products,” in Fermented Milks, ed. Adnan Y. Tamime (Oxford: Blackwell Science, 2006), 156–173.

  • 64. William J. Kelly, Lawrence J. Ward, and Sinead C. Leahy, “Chromosomal Diversity in Lactococcus lactis and the Origin of Dairy Starter Cultures,” Genome Biology and Evolution 2 (2010): 729–744; and Daniel Cavanagh, Gerald F. Fitzgerald, and Olivia McAuliffe, “From Field to Fermentation: The Origins of Lactococcus lactis and Its Domestication to the Dairy Environment,” Food Microbiology 47 (2015): 45–61.

  • 65. Élie Metchnikoff, The Prolongation of Life: Optimistic Studies (London: William Heinemann, 1907), 175.

  • 66. Luba Vikhanski, Immunity: How Elie Metchnikoff Changed the Course of Modern Medicine (Chicago: Chicago Review Press, 2016), 168.

  • 67. Perin Gurel, “Live and Active Cultures: Gender, Ethnicity, and ‘Greek’ Yogurt in America,” Gastronomica 16 (2016): 66–77.

  • 68. Perin Gurel, “Live and Active Cultures: Gender, Ethnicity, and “Greek” Yogurt in America,” Gastronomica 16 (2016): 67.

  • 69. Moore, J Bernadette, Annabelle Horti, and Barbara A Fielding, “Evaluation of the nutrient content of yogurts: a comprehensive survey of yogurt products in the major UK supermarkets,” BMJ Open 8, no. 8 (2018): e021387.

  • 70. Gurel, “Live and Active Cultures,” 67.

  • 71. Donald D. Muir, Adnan Y. Tamime, and Monika Wszołek, “Comparison of the Sensory Profiles of Kefir, Buttermilk and Yogurt,” International Journal of Dairy Technology 52, no. 4 (1999): 129–134.

  • 72. Mohamed A. Farag, Suzan A. Jomaa, Aida Abd El-Wahed, and Hesham R. El-Seedi, “The Many Faces of Kefir Fermented Dairy Products: Quality Characteristics, Flavour Chemistry, Nutritional Value, Health Benefits, and Safety,” Nutrients 12, no. 2 (2020), 11, 16.

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