Kōji (food)

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Kōji (ニホンコウジカビ, 日本麹黴, ‘nihon kōji kabi’) refers to various molds of the genus Aspergillus sp., which are traditionally used in East Asian cuisine for the fermentation of food. In Japanese, kōji refers to both the Aspergillus starter culture and mixtures of Aspergillus with wheat and soybean meal. It can be fried and eaten directly or processed to a sauce.[1]

Characteristics[edit]

Four Aspergillus species in a Petri dish. The bottom two are strains of A. oryzae

Various types of kōji are used, including yellow, black, and white.[2][1] The kōji is stored for two to three days at 30 °C under high humidity to allow A. oryzae to grow.[3] In this process, the starch from cereals such as wheat, buckwheat or barley as well as from sweet potato is split into glucose, creating a sweet taste. Due to the amino acids glutamic acid and to a lesser extent also aspartic acid split off from the proteins during fermentation, a strong umami taste is created on the human tongue when consumed.[4][5] Dried kōji-spores can be stored and transported light-protected at room temperature.

Yellow kōji[edit]

Aspergillus sojae on soybeans

Yellow kōji is used, among other things, for the production of soy sauce,[3][4] miso,[6][7] sake,[8] tsukemono, jiang, makgeolli, meju, tapai, kōji-amazake, rice vinegar,[9] mirin, shio koji[10] and natto. Typically, for the production of soy sauce (shoyu), soybeans and sometimes also wheat are swollen in water, steamed, and possibly mixed with wheat bran roasted at 160–180 °C and ground. The enrichment with kōji creates a moist mash.[3]

There are three Aspergillus species that are used as yellow kōji:

A. oryzae has three α-amylase genes, which allows it to break down starch relatively quickly into glucose.[3] In contrast, A. sojae has only one α-amylase gene under a weak promoter and the CAAT box has a gene expression attenuating mutation (CCAAA instead of CCAAT), but has a higher enzyme activity of endopolygalacturonase and glutaminase.[3] A too rapid release of glucose from starch at the beginning of fermentation inhibits the growth of the microorganisms in the maturation phase.[3] For the breakdown of proteins to amino acids, ‘‘A. oryzae’’ strain RIB40 has 65 endopeptidase genes and 69 exopeptidase genes, and ‘‘A. sojae’’ strain SMF134 has 83 endopeptidase genes and 67 exopeptidase genes.[3] Various mutants of ‘‘A. oryzae’’ with altered properties were generated by irradiation[3] or by the CRISPR/CAS method.[15][16]

Black & white kōji[edit]

Black kōji produces citric acid during fermentation, which inhibits the growth of unwanted microorganisms.[2] It is used for the production of Shochu and Awamori.[2][10]

There are three Aspergillus species that are used as black kōji:[2]

  • Aspergillus luchuensis (synonym Aspergillus awamori, Aspergillus kawachii, Aspergillus inuii, Aspergillus nakazawai and Aspergillus coreanus, クロコウジキン / 黒麹菌 ‘kuro kōji-kin’)
  • Aspergillus niger (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 is an albino variant of Aspergillus luchuensis.[17]

Literature[edit]

  • H. Kitagaki: Medical Application of Substances Derived from Non-Pathogenic Fungi and -Containing. In: Journal of fungi. Band 7, Nummer 4, März 2021, S. , doi:10.3390/jof7040243, PMID 33804991, PMC 8063943.
  • J.E. Smith. Aspergillus. Springer US. pp. 46ff. ISBN 978-1-4615-2411-3.

References[edit]

  1. ^ a b 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. ISBN 978-3-95614-293-2.
  2. ^ a b c d 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, doi:10.1007/s00253-013-5332-9, PMID 24281756 (Review).
  3. ^ a b c d e f g h i 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, doi:10.3390/jof7080658, PMID 34436196, PMC 8399179. (English)
  4. ^ a b c 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, doi:10.1021/acs.jafc.0c04274, PMID 32880168, PMC 7581291. (English)
  5. ^ 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, doi:10.1111/j.1750-3841.2010.01529.x, PMID 20492309.
  6. ^ 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, doi:10.1111/1750-3841.15773, PMID 34056716.
  7. ^ 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, doi:10.3390/jof7070579, PMID 34356958, PMC 8307815.
  8. ^ 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, doi:10.1080/09168451.2019.1625265, PMID 31159661.
  9. ^ Rich Shih, Jeremy Umansky: Koji Alchemy, Chelsea Green 2020. ISBN 978-1-6035-8868-3. p. 13–19.
  10. ^ a b Yoshikatsu Murooka: Japanese Food for Health and Longevity - The Science behind a Great Culinary Tradition. Cambridge Scholars 2020. ISBN 978-1-5275-5043-8. p. 45–65.
  11. ^ 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 doi:10.1186/s40643-021-00408-z, PMID 38650252, PMC 10992763.
  12. ^ a b Martin Weidenbörner (2013). Lexicon of Food Mycology. Springer Berlin Heidelberg. p. 19. ISBN 978-3-642-57058-2.
  13. ^ Keith A. Powell, Annabel Renwick, John F. Peberdy: The Genus Aspergillus: From Taxonomy and Genetics to Industrial Application. Springer, 2013, ISBN 978-1-4899-0981-7, p. 161.
  14. ^ William Shurtleff, Akiko Aoyagi: History of Koji – Grains And/or Soybeans Enrobed with a Mold Culture (300 BCE To 2012). Soyinfo Center, 2012, ISBN 978-1-928914-45-7.
  15. ^ J. I. Maruyama: Genome Editing Technology and Its Application Potentials in the Industrial Filamentous Fungus. In: Journal of fungi. Volume 7, Number 8, August 2021, doi:10.3390/jof7080638, PMID 34436177, PMC 8399504. (English)
  16. ^ 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, doi:10.3389/fmicb.2021.644404, PMID 33708187, PMC 7940364.
  17. ^ T. Futagami: The white koji fungus Aspergillus luchuensis mut. kawachii. In: Bioscience, biotechnology, and biochemistry. Volume 86, Number 5, April 2022, p. 574–584, doi:10.1093/bbb/zbac033, PMID 35238900 (Review).
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