Kōji (, also written as the

kokuji In Japanese, or are kanji created in Japan rather than borrowed from China. Like most Chinese characters, they are primarily formed by combining existing characters - though using combinations that are not used in Chinese. Since kokuji ar ...

) is a filamentous fungus, most commonly ''

Aspergillus oryzae ''Aspergillus oryzae'', also known as , is a mold used in East Asia to saccharify rice, sweet potato, and barley in the making of alcoholic beverages such as '' sake'' and '' shōchū'', and also to ferment soybeans for making soy sauce and '' ...

'', which are traditionally used in Japanese cuisine for the

fermentation Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...

food Food is any substance consumed by an organism for Nutrient, nutritional support. Food is usually of plant, animal, or Fungus, fungal origin and contains essential nutrients such as carbohydrates, fats, protein (nutrient), proteins, vitamins, ...

, or a mixture of such a culture with wheat and soybean meal. The latter can be fried and eaten directly or processed to a

sauce In cooking, a sauce is a liquid, cream, or semi- solid food, served on or used in preparing other foods. Most sauces are not normally consumed by themselves; they add flavour, texture, and visual appeal to a dish. ''Sauce'' is a French wor ...

. René Redzepi, David Zilber: ''The Noma Handbook Fermentation - How to make Koji, Kombucha, Shoyu, Miso, Vinegar, Garum, lacto-fermented and black fruits and vegetables and cook with them.'' 5th edition, A. Kunstmann, 2019. . The term ''kōji'' in English refers specifically to the Japanese types of starter cultures. The same

Chinese character Chinese characters are logographs used to write the Chinese languages and others from regions historically influenced by Chinese culture. Of the four independently invented writing systems accepted by scholars, they represent the only on ...

(, more commonly written as the homophonic in simplified Chinese texts) is used in Chinese to refer to Chinese starter cultures; see

jiuqu ''Jiuqu'', also simply known as ''qu'', is a type of dried fermentation starter used in the production of traditional Chinese alcoholic beverages. The word ''jiuqu'' specifically refers to a type of yeast () used to make alcohol () such as ''huan ...

. In Japanese, the genus ''Aspergillus'' is known with the common name of , though the term is not fully limited to the genus (for example, ''

Monascus purpureus ''Monascus purpureus'' (syn. ''M. albidus'', ''M. anka'', ''M. araneosus'', ''M. major'', ''M. rubiginosus'', and ''M. vini''; zh, s= 红曲霉, t=紅麴黴, p=hóng qū méi, lit. "red yeast") is a species of mold that is purplish-red in colo ...

'' is called "red kōji mold").

Characteristics

Four 3-day old Aspergillus colonies on a Petri dish

Various types of kōji are used, including yellow, black, and white.S. B. Hong, O. Yamada, R. A. Samson: ''Taxonomic re-evaluation of black koji molds.'' In: '' Applied Microbiology and Biotechnology''. Volume 98, Number 2, January 2014, p. 555–561, , PMID 24281756 (Review). The kōji is stored for two to three days at 30 °C under high humidity to allow ''A. oryzae'' to grow. In this process, the

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...

from cereals such as

wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

buckwheat Buckwheat (''Fagopyrum esculentum'') or common buckwheat is a flowering plant in the knotweed family Polygonaceae cultivated for its grain-like seeds and as a cover crop. Buckwheat originated around the 6th millennium BCE in the region of what ...

barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...

as well as from

sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledonous plant in the morning glory family, Convolvulaceae. Its sizeable, starchy, sweet-tasting tuberous roots are used as a root vegetable, which is a staple food in parts of ...

is split into

glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...

, creating a sweet taste. Due to the

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...

glutamic acid Glutamic acid (symbol Glu or E; known as glutamate in its anionic form) is an α- amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can ...

and to a lesser extent also

aspartic acid Aspartic acid (symbol Asp or D; the ionic form is known as aspartate), is an α-amino acid that is used in the biosynthesis of proteins. The L-isomer of aspartic acid is one of the 22 proteinogenic amino acids, i.e., the building blocks of protei ...

split off from the

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, re ...

during fermentation, resulting in a strong

umami Umami ( from ), or savoriness, is one of the five basic tastes. It is characteristic of broths and cooked meats. People taste umami through taste receptors that typically respond to glutamates and nucleotides, which are widely present in me ...

taste.C. Diez-Simon, C. Eichelsheim, R. Mumm, R. D. Hall: ''Chemical and Sensory Characteristics of Soy Sauce: A Review.'' In: ''Journal of agricultural and food chemistry.'' Volume 68, Number 42, October 2020, p. 11612–11630, , PMID 32880168, . (English)H. N. Lioe, J. Selamat, M. Yasuda: ''Soy sauce and its umami taste: a link from the past to current situation.'' In: ''Journal of food science.'' Volume 75, Number 3, April 2010, p. R71–R76, , PMID 20492309. Depending on the Aspergillus used, culture substrate and culture conditions (temperature, pH value, salt content, humidity), different products are created in terms of composition, flavour and odour.T. Futagami: ''The white koji fungus Aspergillus luchuensis mut. kawachii.'' In: ''Bioscience, biotechnology, and biochemistry.'' Volume 86, Issue 5, April 2022, p. 574–584, , PMID 35238900. Kōji can be freeze-dried and crushed to produce spores.N. Chintagavongse, T. Yoneda, C. Ming-Hsuan, T. Hayakawa, J. I. Wakamatsu, K. Tamano, H. Kumura: ''Adjunctive application of solid-state culture products and its freeze-dried powder from Aspergillus sojae for semi-hard cheese.'' In: ''Journal of the science of food and agriculture.'' Volume 100, Issue 13, Oktober 2020, p. 4834–4839, , PMID 32476132. Dried kōji-

spores In biology, a spore is a unit of sexual (in fungi) or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plant ...

can be stored and transported light-protected at room temperature.

Yellow kōji

Yellow kōji is used, among other things, for the production of

soy sauce Soy sauce (sometimes called soya sauce in British English) is a liquid condiment of China, Chinese origin, traditionally made from a fermentation (food), fermented paste of soybeans, roasted cereal, grain, brine, and ''Aspergillus oryzae'' or ''A ...

miso is a traditional Japanese seasoning. It is a thick paste produced by fermenting soybeans with salt and kōji (the fungus ''Aspergillus oryzae''), and sometimes rice, barley, seaweed, or other ingredients. It is used for sauces and spreads; p ...

,J. G. Allwood, L. T. Wakeling, D. C. Bean: ''Fermentation and the microbial community of Japanese koji and miso: A review.'' In: ''Journal of food science.'' Volume 86, Number 6, June 2021, p. 2194–2207, , PMID 34056716.K. I. Kusumoto, Y. Yamagata, R. Tazawa, M. Kitagawa, T. Kato, K. Isobe, Y. Kashiwagi: ''Japanese Traditional and Making.'' In: ''Journal of fungi.'' Volume 7, Number 7, July 2021, , PMID 34356958, .

sake Sake, , or saki, also referred to as Japanese rice wine, is an alcoholic beverage of Japanese origin made by fermenting rice that has been polished to remove the bran. Despite the name ''Japanese rice wine'', sake, and indeed any East Asi ...

,K. Gomi: ''Regulatory mechanisms for amylolytic gene expression in the koji mold.'' In: ''Bioscience, biotechnology, and biochemistry.'' Volume 83, Number 8, August 2019, p. 1385–1401, , PMID 31159661.

tsukemono are Japanese preserved vegetables (usually pickled in salt, brine, or a bed of rice bran). They are served with rice as an '' okazu'' (side dish), with drinks as an '' otsumami'' (snack), as an accompaniment to or garnish for meals, and a ...

, jiang,

makgeolli ''Makgeolli'' (), sometimes anglicized to makkoli (, ), is a Korean alcoholic drinks, Korean alcoholic drink. It is a milky, off-white, and lightly sparkling rice wine that has a slight viscosity, and tastes slightly sweet, tangy, bitter, and astr ...

meju ''Meju'' () is a brick of dried fermented soybeans. While not consumed on its own, it serves as the basis of several Korean condiments, such as '' doenjang'' (soybean paste), '' ganjang'' (soy sauce), and gochujang (chili paste). ''Meju'' is prod ...

tapai ''Tapai'' (also ''tapay'' or ''tape'') is a traditional fermented preparation of rice or other starchy foods, and is found throughout much of Southeast Asia, especially in Austronesian cultures, and parts of East Asia. It refers to both th ...

, kōji-

amazake is a traditional sweet, low-alcohol or non-alcoholic Japanese drink made from fermented rice. ''Amazake'' dates from the Kofun period, and it is mentioned in the Nihon Shoki. It is part of the family of traditional Japanese foods made using ...

rice vinegar Rice vinegar is a vinegar made from rice wine in East Asia (China, Japan and Korea), as well as in Vietnam in Southeast Asia. It is used as a seasoning, dressing, and dipping in many dishes, including sushi, jiaozi, and banchans. Some of its varia ...

,Rich Shih, Jeremy Umansky: ''Koji Alchemy'', Chelsea Green 2020. . p. 13–19.

mirin is a type of rice wine and a common ingredient in Japanese cuisine, Japanese cooking. It is similar to sake but with a lower alcohol (drug), alcohol content and higher sugar content. The sugar content is a complex carbohydrate that forms natur ...

, shio kojiYoshikatsu Murooka: ''Japanese Food for Health and Longevity - The Science behind a Great Culinary Tradition.'' Cambridge Scholars 2020. . p. 45–65. and natto. Typically, for the production of soy sauce (''shoyu''),

soybeans The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source of f ...

and sometimes also wheat are swollen in water,

steamed Steaming is a method of cooking using steam. This is often done with a food steamer, a kitchen appliance made specifically to cook food with steam, but food can also be steamed in a wok. In the American Southwest, steam pits used for cooking ha ...

, and possibly mixed with wheat bran roasted at 160–180 °C and ground. The enrichment with kōji creates a moist mash.K. Ito, A. Matsuyama: ''Koji Molds for Japanese Soy Sauce Brewing: Characteristics and Key Enzymes.'' In: ''Journal of fungi.'' Volume 7, Number 8, August 2021, , PMID 34436196, . There are three Aspergillus species that are used as yellow kōji: * '' Aspergillus flavus var. oryzae''Ghoson M. Daba, Faten A. Mostafa, Waill A. Elkhateeb: ''The ancient koji mold (Aspergillus oryzae) as a modern biotechnological tool.'' In: ''Bioresources and bioprocessing.'' 2021, Volume 8, Number 1 , PMID 38650252, . (キコウジキン / 黄麹菌 ‘ki kōji-kin’). The growth range of this species includes pH values from below 2 to above 8, a temperature optimum of 32 – 36 °C, a temperature minimum of 7 – 9 °C and a temperature maximum of 45 – 47 °C. The colony color is initially yellow-green, later more or less brown. * '' Aspergillus sojae'' (醤油麹菌 ‘shōyu-kōji-kin’) * '' Aspergillus tamarii'' ''A. oryzae'' has three α-

amylase An amylase () is an enzyme that catalysis, catalyses the hydrolysis of starch (Latin ') into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large ...

genes, which allows it to break down starch relatively quickly into glucose. In contrast, ''A. sojae'' has only one α-amylase gene under a weak promoter and the

CAAT box In molecular biology, a CCAAT box (also sometimes abbreviated a CAAT box or CAT box) is a distinct pattern of nucleotides with GGCCAATCT consensus sequence that occur upstream by 60–100 bases to the initial transcription site. The CAAT box sig ...

has a gene expression attenuating mutation (CCAAA instead of CCAAT), but has a higher

enzyme activity Enzyme assays are laboratory methods for measuring enzyme, enzymatic activity. They are vital for the study of enzyme kinetics and enzyme inhibitor, enzyme inhibition. Enzyme units The quantity or concentration of an enzyme can be expressed in Mo ...

of endopolygalacturonase and

glutaminase Glutaminase (, ''glutaminase I'', ''L-glutaminase'', ''glutamine aminohydrolase'') is an amidohydrolase enzyme that generates glutamate from glutamine. Glutaminase has tissue-specific isoenzymes. Glutaminase has an important role in glial cell ...

. A too rapid release of glucose from starch at the beginning of fermentation inhibits the growth of the microorganisms in the maturation phase. For the breakdown of proteins to amino acids, ''A. oryzae'' strain RIB40 has 65

endopeptidase Endopeptidase or endoproteinase are proteolytic peptidases that break peptide bonds of nonterminal amino acids (i.e. within the molecule), in contrast to exopeptidases, which break peptide bonds from end-pieces of terminal amino acids. For this r ...

genes and 69

exopeptidase An exopeptidase is any peptidase that catalyzes the cleavage of the terminal (or the penultimate) peptide bond; the process releases a single amino acid, dipeptide or a tripeptide from the peptide chain. Depending on whether the amino acid is r ...

genes, and ''A. sojae'' strain SMF134 has 83 endopeptidase genes and 67 exopeptidase genes. Similarly, starch-degrading enzymes (glucosidases) are more strongly expressed and protein-degrading enzymes (proteases) less strongly expressed in ''A. oryzae'', and the odour profiles differ significantly.J. Li, B. Liu, X. Feng, M. Zhang, T. Ding, Y. Zhao, C. Wang: ''Comparative proteome and volatile metabolome analysis of Aspergillus oryzae 3.042 and Aspergillus sojae 3.495 during koji fermentation.'' In: ''Food research international.'' Band 165, März 2023, S. 112527, , PMID 36869527. ''A. sojae'' has 10 glutaminase genes.K. Ito, Y. Hanya, Y. Koyama: ''Purification and characterization of a glutaminase enzyme accounting for the majority of glutaminase activity in Aspergillus sojae under solid-state culture.'' In: '' Applied Microbiology and Biotechnology.'' Band 97, Nummer 19, Oktober 2013, S. 8581–8590, , PMID 23339014. Various

mutant In biology, and especially in genetics, a mutant is an organism or a new genetic character arising or resulting from an instance of mutation, which is generally an alteration of the DNA sequence of the genome or chromosome of an organism. It i ...

s of ''A. oryzae'' with altered properties were generated by

irradiation Irradiation is the process by which an object is exposed to radiation. An irradiator is a device used to expose an object to radiation, most often gamma radiation, for a variety of purposes. Irradiators may be used for sterilizing medical and p ...

or by the CRISPR/CAS method.J. I. Maruyama: ''Genome Editing Technology and Its Application Potentials in the Industrial Filamentous Fungus.'' In: ''Journal of fungi.'' Volume 7, Issue 8, August 2021, S. , , PMID 34436177, .F. J. Jin, S. Hu, B. T. Wang, L. Jin: ''Advances in Genetic Engineering Technology and Its Application in the Industrial Fungus.'' In: ''Frontiers in Microbiology.'' Volume 12, 2021, p. 644404, , PMID 33708187, .T. Katayama, J. I. Maruyama: ''CRISPR/Cpf1-mediated mutagenesis and gene deletion in industrial filamentous fungi Aspergillus oryzae and Aspergillus sojae.'' In: ''Journal of bioscience and bioengineering.'' Volume 133, Issue 4, April 2022, p. 353–361, , PMID 35101371. Similarly, mutants of ''A. sojae'' with altered properties were generated by a variant of the CRISPR/Cas method or chemical mutagenesis.J. Lim, Y. H. Choi, B. S. Hurh, I. Lee: ''Strain improvement of for increased l-leucine aminopeptidase and protease production.'' In: ''Food science and biotechnology.'' Volume 28, Issue 1, February 2019, p. 121–128, , PMID 30815302, .

Black & white kōji

Black kōji produces

citric acid Citric acid is an organic compound with the formula . It is a Transparency and translucency, colorless Weak acid, weak organic acid. It occurs naturally in Citrus, citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, ...

during fermentation, which inhibits the growth of unwanted microorganisms. It is typically used for the production of

awamori ''Awamori'' (, Okinawan: , ) is an alcoholic beverage indigenous and unique to Okinawa, Japan. It is made from long grain indica rice, and is not a direct product of brewing (like ''sake'') but of distillation (like ''shōchū''). The majorit ...

. There are three Aspergillus species that are used as black kōji: * ''

Aspergillus luchuensis ''Aspergillus luchuensis'' (previous names ''A. foetidus'' and ''A. acidus'') is a species of fungus in the genus ''Aspergillus''. It belongs to the group of black ''Aspergilli'' which are important industrial workhorses. The fungus has been used ...

'' (synonym ''Aspergillus awamori'', ''Aspergillus inuii'', ''Aspergillus nakazawai'' and ''Aspergillus coreanus'', クロコウジキン / 黒麹菌 ‘kuro kōji-kin’) * ''

Aspergillus niger ''Aspergillus niger'' is a mold classified within the ''Nigri'' section of the ''Aspergillus'' genus. The ''Aspergillus'' genus consists of common molds found throughout the environment within soil and water, on vegetation, in fecal matter, on de ...

'' (synonym ''Aspergillus batatae'', ''Aspergillus aureus'' or ''Aspergillus foetidus'', ''Aspergillus miyakoensis'' and ''Aspergillus usamii'' including ''A. usamii mut. shirousamii'') * '' Aspergillus tubingensis'' (synonym ''Aspergillus saitoi'' and ''A. saitoi var. kagoshimaensis'') White kōji (''Aspergillus kawachii'') is an

albino Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and reddish pink or blue eyes. Individuals with the condition are referred to as albinos. Varied use and interpretation of ...

variant of ''Aspergillus luchuensis''. It is typically used in the production of

shōchū is a Japanese distilled beverage. It is typically distilled from rice, barley, sweet potatoes, buckwheat, or brown sugar, though it is sometimes produced from other ingredients such as chestnut, sesame seeds, potatoes, or even carrots. Typ ...

History

''麹'' (Chinese ''qū'', Japanese ''kōji'') which means mold used in fermented foods, was first mentioned in the ''Zhouli'' ( Rites of the Zhou dynasty) in China in 300 BCE. Its development is a milestone in Chinese food technology, for it provides the conceptual framework for three major fermented soy foods:

, '' jiang''/''

'', and ''

douchi ''Douchi'' is a type of fermented and salted black soybean most popular in the cuisine of China, where they are most widely used for making black bean sauce dishes. Shurtleff, W.; Aoyagi, Abr>History of Fermented Black Soybeans (165 B.C. to ...

'', not to mention grain-based wines (including Japanese ''

'' and Chinese ''

huangjiu ''Huangjiu'' () is a type of Chinese rice wine (''mijiu'') most popular in the Jiangnan area. ''Huangjiu'' is brewed by mixing steamed grains including rice, glutinous rice or millet with ''qū'' as starter culture, followed by saccharifica ...

'') and ''li'' (the Chinese forerunner of Japanese ''

''). The process of making rice wine and fermented bean paste using molds was first documented in the 4th century B.C. In 725 AD the Japanese book ''Harima no Kuni Fudoki'' ('Geography and Culture of the Harima Province') first mentioned kōji outside of China and described that the Japanese produced kōji with fungal spores from the air. Around the 10th century, the kōji production method underwent a change and moved from the natural sowing system in rice to the so-called ''tomodane''. This involved cultivating kōji until spores were released and using the spores to start a new batch of production. In the Meiji era, the integration of new microbiological techniques made it possible to isolate and propagate kōji in pure cultures for the first time. These advances facilitated the improvement of mushroom culture quality and the selection of desirable characteristics. It later became known that Kōji comprises different species of Aspergillus. ''Aspergillus oryzae'' was first described in 1878 as ''Eurotium oryzae'' Ahlb. and in 1883 as ''Aspergillus oryzae'' (Ahlb.) Cohn.Index Fungorum
''Names Record A. oryzae''
accessed 15. Mai 2024. ''Aspergillus luchuensis'' was first described in 1901 by Tamaki Inui at the University of Tokyo. Genichiro Kawachi isolated a colourless mutant of ''A. luchuensis'' (black Kōji) in 1918 and named it ''Aspergillus kawachii'' (white Kōji). ''Aspergillus sojae'' was first described as a distinct species in Kōji in 1944.Katsumi Yuasa, Kazuya Hayashi, Takeji Mizunuma: ''A new criterion by which to distinguish Aspergillus sojae, a Kōji-mold, from related taxa producing echinulate conidia.'' In: ''Agricultural and biological chemistry.'' 1982, Volume 46, Nummer 6, p. 1683–1686 .Index Fungorum
''Names Record A. sojae''
accessed 15. Mai 2024. Initially, ''Aspergillus sojae'' was considered a variety of ''

Aspergillus parasiticus ''Aspergillus'' () is a genus consisting of several hundred mold species found in various climates worldwide. ''Aspergillus'' was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli. Viewing the fungi under a microsc ...

'' because, unlike the other fungi of Kōji, it had never been isolated from the soil.Perng‐Kuang Chang, Kei Matsushima, Tadashi Takahashi, Jiujiang Yu, Keietsu Abe, Deepak Bhatnagar, Gwo Fang Yuan, Yasuji Koyama, Thomas E. Cleveland: ''Understanding nonaflatoxigenicity of Aspergillus sojae: a windfall of aflatoxin biosynthesis research.'' In: '' Applied Microbiology and Biotechnology.'' 2007, Volume 76, Nummer 5, p. 977–984 .

Traditional Uses

Koji is widely used in traditional fermentation processes to create staple foods and condiments: *

Miso is a traditional Japanese seasoning. It is a thick paste produced by fermenting soybeans with salt and kōji (the fungus ''Aspergillus oryzae''), and sometimes rice, barley, seaweed, or other ingredients. It is used for sauces and spreads; p ...

: A fermented soybean paste that is a cornerstone of Japanese cuisine. Its production involves combining koji (usually rice-based) with cooked soybeans and salt, followed by fermentation for weeks or even years.

Enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

s in the koji break down complex proteins and carbohydrates in the soybeans, creating miso's rich and nuanced flavor. The

time, type of koji, and additional ingredients all contribute to a wide variety of miso types, from sweet white miso to robust red miso. Miso adds depth and complexity to dishes such as soups, stews, marinades, and sauces. *

Sake Sake, , or saki, also referred to as Japanese rice wine, is an alcoholic beverage of Japanese origin made by fermenting rice that has been polished to remove the bran. Despite the name ''Japanese rice wine'', sake, and indeed any East Asi ...

: In sake production, koji converts rice starch into fermentable sugars. Unlike beer brewing, where saccharification and fermentation occur sequentially, sake brewing integrates these stages in a parallel fermentation environment. This dynamic interplay contributes to sake’s unique flavor profile. Koji not only facilitates starch conversion but also develops nuanced aromas and flavors in the final product. *

Soy Sauce Soy sauce (sometimes called soya sauce in British English) is a liquid condiment of China, Chinese origin, traditionally made from a fermentation (food), fermented paste of soybeans, roasted cereal, grain, brine, and ''Aspergillus oryzae'' or ''A ...

: A fermented condiment derived from soybeans and wheat, with koji initiating enzymatic breakdown. Koji is cultivated on roasted wheat and soybeans and then mixed with salt water to create a brine called moromi, which ferments for months. Koji enzymes break down proteins and starches, contributing to soy sauce's

flavor. After fermentation, the moromi is pressed, pasteurized, filtered, and bottled.

Modern Applications

Recent advancements in food technology have expanded the applications of koji beyond traditional uses.

Meat Alternatives

Most meat substitutes on the market today are derived from legumes such as soybeans and peas. While these proteins can effectively replicate the taste and texture of meat, they present challenges including high agricultural land and water use, allergenic concerns, and distinct flavors that may not appeal to all consumers. To address these issues, scientists are exploring microbial fermentation as a more sustainable protein source. There are two main methods for producing protein from microorganisms:

precision fermentation Industrial fermentation is the intentional use of fermentation in manufacturing processes. In addition to the mass production of fermented foods and drinks, industrial fermentation has widespread applications in chemical industry. Commodity chem ...

, which involves engineering microbes to produce specific proteins, and biomass fermentation, where fungi or other microbes are cultivated as whole-food protein sources. A particularly promising organism in this space is mycelium—the protein-rich, fibrous root structure of fungi. Among microbial sources, koji (''

'') is at the forefront of this innovation due to its long-standing use in food and established regulatory approvals. It is recognized as Generally Recognized as Safe (GRAS) by the U.S. FDA and classified as non-novel by the European Food Safety Authority (EFSA), facilitating commercialization. Companies like Prime Roots, based in California, are leveraging koji to create meat alternatives with a fibrous texture similar to animal meat. Koji is cultivated in fermentation vats where it forms long, muscle-like strands. These strands are then combined with plant-based fats and natural flavors to create realistic meat substitutes. Berlin-based Nosh.bio is advancing single-ingredient koji-based meat products. In collaboration with Zur Mühlen, a leading European sausage producer, Nosh.bio is commercializing its Koji Protein as a sustainable meat alternative. Koji’s minimal processing, allergen-friendly nature, and regulatory status make it a sustainable and scalable option for the future of alternative proteins.

Flavor Enhancement

In addition to its use in protein innovation, koji is gaining popularity among chefs and food technologists for its powerful enzymatic properties that enhance flavor. Modern culinary applications of koji include:https://onimapantry.com/blogs/blog/koji-how-fermentation-unlocks-depth-umami-and-flavor * Dry-aging meats: Applying koji spores to meat breaks down proteins, accelerating the aging process and resulting in more tender, flavorful cuts. * Fermenting vegetables: Koji is used to ferment vegetables like cabbage, carrots, and beets, producing umami-rich flavors while preserving crisp textures. * Vegan condiments: Koji enables the production of soy-free, plant-based sauces that deliver deep, savory flavors without the use of animal products. These culinary innovations highlight koji's versatility beyond traditional Japanese cuisine and demonstrate its growing role in sustainable and creative cooking worldwide.

Nutritional and Health Benefits

Koji provides a range of nutrients and bioactive compounds that contribute to its potential health-promoting properties. It is a source of B-vitamins, including B1, B2, B3, B6, B12, biotin (vitamin H), folic acid, and iron.https://www.ichizen-japan-restaurant.ch/post/_koji The fermentation process enhances its nutritional profile by generating enzymes, amino acids, and minerals that support physiological functions. Additionally, koji is considered a low glycemic index (GI) food, which may contribute to improved blood sugar regulation. Fermentation also enhances nutrient bioavailability and introduces beneficial compounds such as bioactive peptides, polysaccharides, and glycosylceramide. Glycosylceramide, notably, resists digestion but interacts with gut microbiota in ways that may promote gut health.https://pmc.ncbi.nlm.nih.gov/articles/PMC4980852/

Digestive and Gut Health

Like other fermented foods, koji may support digestive health due to its enzyme and probiotic content. Enzymes aid in the breakdown of macronutrients, improving digestion and nutrient absorption.https://cookingwithyoshiko.com/the-japanese-food-that-will-revolutionise-your-health/ Koji also acts as a prebiotic, promoting the growth of beneficial intestinal bacteria such as ''Blautia coccoides''. This bacterium is associated with various health benefits and may play a role in the observed connection between traditional Japanese diets, gut microbiota, and longevity. Regular consumption of koji-fermented foods may help maintain microbiome diversity, which is increasingly recognized as important for overall health.

Metabolic Health

Due to its low glycemic index, koji may help stabilize blood sugar levels and support energy regulation. Sustained energy release and improved satiety may aid in weight management. Some studies suggest koji-fermented soy products may contribute to improved cholesterol profiles, although further research is needed to confirm the mechanisms. Fermentation products and dietary fiber in koji-based foods may also contribute to cardiovascular health through metabolic regulation.

Skin Health

Koji has been traditionally used for its potential skin health benefits. Nutrients such as biotin, vitamins, and amino acids may support skin elasticity, brightness, and hydration. Antioxidants in koji may protect skin from oxidative damage and environmental stressors, potentially slowing visible signs of aging. Furthermore, the gut-skin axis suggests that gut microbiota modulation through koji consumption may indirectly benefit skin health.

Immune Function

Koji may support immune regulation through gut-immune interactions fostered by its probiotic and prebiotic effects. A healthy gut microbiome has been associated with reduced inflammation and enhanced immune response. The antioxidants present in koji may also contribute to cellular protection by neutralizing free radicals, potentially lowering the risk of chronic diseases and slowing aging processes.

Literature

* H. Kitagaki: ''Medical Application of Substances Derived from Non-Pathogenic Fungi and -Containing.'' In: ''Journal of fungi.'' Band 7, Nummer 4, März 2021, S. , , PMID 33804991, . * {{cite book, author=J. E. Smith, title=Aspergillus, date=6 December 2012 , url=https://books.google.com/books?id=S6LfBwAAQBAJ&pg=PA, publisher=Springer US , isbn=978-1-4615-2411-3, pages=46ff

References

Foods Japanese cuisine Fermentation in food processing