Barley
Barley is a hardy cereal, domesticated in the Middle East over 10,000 years ago, eaten whole, pearled or milled, malted for brewing, and grown with koji mold for barley miso.
Modern adaptation
Barley koji
Nordic Food Lab barley koji
Steamed pearled barley grown into a white koji cake with Aspergillus oryzae over about 36 hours in a 30 °C chamber, turned three times under a damp cloth.
Growing koji on barley
Koji is a grain grown with an Aspergillus oryzae culture. The Nordic Food Lab grew it on pearled barley, its mainstay substrate. The barley is soaked overnight, steamed for 90 minutes, cooled and inoculated at 35 °C with powdered spores, then incubated at 30 °C for about 36 hours.
The grain is turned and furrowed at 18, 24 and 30 hours to shed heat and let air in. The lab's cake is ready when the mycelium binds the grain into a spongy white mass. Its yield is about 1,450 g from 1 kg of dry barley.
Sources for this section
Heat, spores and what goes wrong
The lab set the grain between 25 and 30 °C after the first turn and treated anything above 38 °C as fatal to the mould. Overheated koji smells of ammonia and sour bananas and is discarded. BCCDC gives 40 °C as the commercial ceiling for enzyme production.
Spores should be bought for each batch. BCCDC advises against saving spores from a koji, because wild Aspergillus strains can make aflatoxin. The sources give about 20 g of spores per kilogram of cooked barley in the method and about 30 g in the lab's equipment list.
Sources for this section
Equipment
The lab's chamber was a switched-off upright fridge fitted with a heating mat and a probe on a PID controller. This is the documented route. A proofer or a controlled cabinet is an adaptation. The electrical arrangement is a historical research-kitchen build and is not a specification.
Sources for this section
History
The Nordic Food Lab published this method in 2013, with its own chamber. The history of barley koji is not researched beyond the lab post.
Ingredients
Yield 1450 g · Scaling: source batch only
Pearled barley, drySoak overnight, then steam for 90 minutes.
1 kg
Koji spores (koji-kin / tane-koji), powderedBlitz to a fine powder.
20 g
About 20 g per kg of cooked barley. The lab's equipment list gives about 30 g.WaterFor soaking and steaming.
Amount not stated
Method
Risks and precautions · Standard risk
Overheating and Bacillus subtilis takeover
Sticky koji that smells of ammonia and sour bananas means the mould died from excess heat and B. subtilis took over. Discard it.
Hazard sourceAflatoxin risk from home-propagated spores
The lab post describes letting koji sporulate to save spores. BCCDC advises against back-slopping, because wild Aspergillus strains can make aflatoxin.
Hazard sourceProbe the grain; turn and furrow it to shed heat.
Control sourceBuy commercial spores for each batch.
Control sourceDiscard koji that turns sticky and ammoniated.
The lab's fridge, mat and controller are a historical research-kitchen build. Use enclosed, rated equipment.
- Soak the pearled barley overnight.
- The next morning, switch the chamber on at 30 °C.
- Steam the barley at 100 °C for 90 minutes in a perforated tray.
- While it cools, grind the spores to a fine powder.
- With sanitised hands and gloves, break up the barley and spread it about 2 cm deep in trays.
- Prepare a warm, damp, wrung-out cloth.
- When the barley reaches 35 °C, sprinkle on the spores, mix to coat every grain, smooth the surface and cover it with the cloth.
- Put the tray in the chamber (time zero), on the top shelf with the probe in the barley. Keep the grain near 30 °C.
- At 18 hours, turn and mix the koji, re-dampen the cloth and return it. For the next 18 hours keep the grain at 25 to 30 °C and never above 38 °C, which the lab treats as fatal to the mould.
- At 24 hours, turn again and plough two deep lengthwise furrows. Re-dampen the cloth and leave the chamber door open a crack.
- At 30 hours, turn and furrow again, lightly re-dampen the cloth, and leave the door ajar.
- At about 36 hours the mycelium binds the grain into a spongy white cake. Use it while it is still white.
Conditions
Yield1450 g
Fermentation36 h
Temperature25–30°C
Places
Denmark
Modern adaptation · Country evidenceThe Nordic Food Lab research kitchen, where barley was the mainstay substrate.
Related
Made from
Yellow-koji starter
Yellow-koji starter is the spore inoculum of the yellow koji mold — Aspergillus oryzae and the related A. sojae — sold by specialist tane-kōji houses to grow koji for sake, miso and soy sauce.
What to make with it
Barley miso (mugi miso)
A Japanese soybean paste fermented with barley koji and salt, made mostly in Kyushu, Shikoku and western Japan. It is sweet, savoury and grainy.
Variants
Rice koji
Rice koji is steamed white rice through which koji mold has grown. It carries the enzymes that turn rice starch into sugar, and it is the starting point of sake, sweet miso, amazake and shio koji.
Equipment
Plug-in temperature controller
A plug-in controller reads a wired probe and switches compatible heating or cooling appliances around a setpoint. It adds feedback; it is not itself a heater, cooler or validated food process.
Plug-in temperature controller on an appliance
An appliance plugged into an external controller so a probe, rather than the appliance's own dial, decides when it heats or cools.
Seedling heat mat
A thin electric mat warms a propagation tray from below; some models use a separate thermostat and probe. One Vivosun manual also gives generic fermentation-heater instructions, but does not validate a particular fermented food or process.
Shallow breathable koji tray
A koji-buta is a shallow wooden tray for spreading grain as it grows into koji. Japanese sources document a traditional form, while modern methods also use cloth-lined or steel trays; size and construction vary.
Warm cabinet with an internal food container
Any warm box, proofer, dehydrator cabinet or adapted fridge whose conditions reach the food through a separate container chosen for that culture.
Pairs with
Mame-koji
Japanese soybean koji: steamed soybeans, loose or formed into balls, grown over with Aspergillus mould to make the enzymes for mame-miso, tamari and regional soybean condiments.
Read more
Fermentation cabinets: proofers, dehydrators and converted fridges
A proofer, a dehydrator with its trays out or an old fridge on a controller can keep cultures at a steady temperature. Whether it works depends on what sits inside: a lidded jar, a vented bag, a shallow tray or a crock.
More from Denmark
Barley and oat porridge (Viking Age)
Crushed or milled barley cooked in water until the starch softens and the mixture thickens, the plainest way a northern household turned stored grain into a meal, here with apple and hazelnut.
Broad-bean mash (modern reconstruction)
Cooked broad beans crushed to a thick paste with garlic and salt, a museum preparation built on the one European pulse that was already old when the Viking Age began.
Dried fruit and berries (Viking Age, reconstructed)
Apple slices dried until most of their water has gone, shrinking and concentrating into leathery or crisp rings, with the modern controls that a plausible old technique turns out to need.
Fish and onion soup (modern reconstruction)
Trout or salmon poached at the end of a simmered broth of onion and root vegetables, a present-day reconstruction of coastal cooking built on excavated fish bones and a boiling pot.
Lamb, barley and cabbage pottage (modern reconstruction)
Lamb shoulder simmered with pearl barley, turnip and leafy cabbage in one pot, a present-day reconstruction built from the animals, grains and vegetables of northern European farming.
Mushroom garum (koji garum)
Mushroom garum is a savoury, smoked sauce made by crushing mushrooms with salt and rice koji and letting the mixture brew for months, a modern use of the garum method without fish.
Remoulade (Danish)
Danish remoulade is a thick, yellow, mayonnaise-based sauce flecked with finely chopped pickled vegetables. Arla’s quick home version stirs piccalilli remoulade purée with mayonnaise, crème fraîche, diced apple and capers.
Rugbrød
This Danish sourdough loaf combines wheat flour and kernels with rye flour and cracked rye, then rises in three tins before a long, low finishing bake.
Related in the family
Ama-koji
A thick, naturally sweet rice-and-koji preparation used to add body and sweetness to marinades, dressings and sauces. This method follows a published Marukome home recipe and is an enzyme-conversion hold, not a way to grow koji mould.
Jiuniang (sweet fermented glutinous rice)
Chinese sweet fermented glutinous rice: steamed rice and a mixed jiuqu starter, where mould enzymes release sugar and yeast makes a little alcohol, eaten with its sweet liquid.
Marcha
An ethnographic record of marcha (murcha), a dry starter cake used in Eastern Himalayan cereal fermentations. This page documents source-specific community knowledge and is not a recipe for making or storing starter.
Rice-koji amazake
Cooked rice, rice koji and water are held warm for hours so koji enzymes turn the rice starch to sugars, giving a naturally sweet Japanese drink with no added sugar and no second fermentation.
Shio koji, rice-koji salt seasoning
A Japanese seasoning of rice koji, salt and water, left at room temperature until the koji's enzymes and its microbes turn it into a savoury, salty paste for marinades and dressings.
Shio-koji
Shio-koji is a Japanese seasoning of rice koji, salt and water, left at room temperature until the grains soften and turn sweet and the mixture thickens.
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Sources
Nordic Food LabMethod · Equipment · History
Koji – history and processfull method and timings
chamber description
yield 1,450 g
troubleshooting
Cited in: Growing koji on barley; Heat, spores and what goes wrong; Equipment
BC Centre for Disease Control, Fermented Foods Working GroupSafety
Fermented Foods Guideline – Section 3.10 Koji and Misono back-slopping; commercial spores
40 °C commercial ceiling
storage
Cited in: Heat, spores and what goes wrong