Skip to main content
Support

Browse by category

All categories
Home

Meat from International

Koji-cured and koji-aged meats

Koji-aged meat is meat coated in koji, rice grown with the mould Aspergillus oryzae, so that the mould's proteases tenderise it and build savoury flavour. In one study, koji powder hydrated into a paste was rubbed on Angus beef at 2 % of its weight and held at 2–4 °C for 72 h. It is a modern chef technique, not a traditional ferment.

Fully documentedMeat7.1 days – 7.2 days

Recipe

Amounts from a sourceAmounts from one university study on Angus beef (Filip et al. 2026). Chef practice varies.
Koji powder2 g per 100 g of meat (2 % w/w)Grown on cooked, cooled rice, dried to 3–5 % moisture and ground[filip2026]
Water1.5 parts water to 1 part koji powder (w/w)To hydrate the powder into a paste[filip2026]
Fine non-iodised salt25 % of the koji powder massFor the shio-koji version only[filip2026]
Beef cutsNeck (chuck) and round of Aberdeen Angus in the study[filip2026]
Starterkoji (Aspergillus oryzae grown on rice)

Total time across the recorded steps: 7.1 days – 7.2 days

Start
Drag the bar or press Play
shapes, not to countAspergillus oryzae25–33 °C

What changes: Koji mould spreads through cooked rice, which is then dried and ground

Step 1 of 5
Grow and dry the koji
Time
4 days
Reported
Temperature
25–33 °C
Reported
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Aspergillus oryzae
Moulds

The koji is then dried to 3–5 % moisture and finely ground.

Flavour
Not documented
Texture
Not documented
Colour
Not documented

Microbes at work in this step

Aspergillus oryzae grows through the rice and makes proteases and amylases

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

At a glance

Koji-aged meat is meat coated in koji, rice grown with the mould Aspergillus oryzae, so that the mould's proteases tenderise it and build savoury flavour. In one study, koji powder hydrated into a paste was rubbed on Angus beef at 2 % of its weight and held at 2–4 °C for 72 h. It is a modern chef technique, not a traditional ferment. Made in 5 steps over 7.1 days – 7.2 days. The longest step, grow and dry the koji, takes 4 days (Filip C 2026) and runs at 25–33 °C (Filip C 2026). Aspergillus oryzae, applied as koji; its proteases (about 800 U/g, as specified by the supplier of the study's powder) break down muscle proteins does most of the fermenting.

Key numbers
Main step4 daysReported[filip2026]Grow and dry the koji
Temperature25–33 °CReported[filip2026]Grow and dry the koji

What makes this one different

Koji ageing borrows the mould of miso and sake and puts its enzymes to work on meat within days. The mould is grown first on rice, and the meat itself is not fermented by bacteria.

Related ferments

Variants

  • Shio-koji marinadeKoji with 25 % salt (of the koji mass), hydrated into a paste and rinsed off after ageing. In a lab test, proteases from commercial shio-koji broke down bovine myofibrils, and did so less at 4 °C than at 37 °C.
  • Koji-shiitake mix70 % koji powder and 30 % shiitake powder.

Safety

The study aged the beef under refrigeration at 2–4 °C for 72 h, and cooked it before the tasting.

History and sources

Every number is labelled with how it is known. How this atlas is made

Koji Alchemy (2020) by Rich Shih and Jeremy Umansky is one of the English-language koji resources for professional settings. Hey and Michael (2025) quote it calling koji a "powerhouse of enzymes" and cite koji-aged charcuterie as one of koji's new uses outside Japanese cooking.

  1. [filip2026] Filip C., Nyulas V.A., Czinege M., Puscas A., Tero-Vescan A. et al. 2026, The effect of Aspergillus oryzae (koji) on the physicochemical and sensory characteristics and satiating capacity of Angus beef, Foods 15(8):1296paper
  2. [hey2025] Hey M., Michael E. 2025, "A whole new world of possibilities", koji uses and ambiguities on the global marketplace, Food, Culture & Society 28(2):365paper
  3. [miyaguchi2026] Miyaguchi Y., Suzuki M., Tohyama K., Yamamoto E. 2026, Effect of proteases in fraction in commercial shio-koji on the proteolysis of bovine myofibrils, Animal Science Journal 97, e70188 (abstract)paper