Or peaso, rather – I used locally grown organic peas from Straigiai farm instead of soybean. All instructions and ideas were taken from the Noma’s guide to fermentation, most likely also available here.

Miso is made via double fermentation: first one has to grow a specific mould (Aspergillus oryzae) on grains (usually rice or barley) – the enzymatic activity of the mould converts starches into sugars. Then the mouldy grain (called koji) are mixed with steamed legumes (soy beans, peas, etc.), salt, and lacto-fermented for several months. The mould is quite sensitive to temperature, moisture and possible bacterial contamination.

For instance, growing A. oryzae on steamed barley it is necessary to allow the grains to breathe and avoid moisture pooling at the bottom. I designed a perforated tray that fits inside the incubator in our biolab using boxes.py, then laser-cut it.

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In order to avoid introducing unpleasant flavour to the koji, I lined the tray with foil and stabbed it 256 times. Then I sterilised some cloth in an autoclave, lined the tray with it and added the steamed and cooled grain.

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I had bought Aspergillus oryzae spores from fermentationculture.eu some months ago – they are based in Europe, ship quickly and have a lot of information about growing.

It is best to mix the spores with flour to help it mix evenly. I sterilised some flour in the autoclave – there were some clumps, but I sieved them out.

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Working in the laminar hood, I mixed the spores with flour:

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Then dusted the flour/spore mixture over cooled barley and mixed everything together with gloved hands.

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The mixture went into the incubator, set on 32 C.

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I monitored the temperature of koji using a thermocouple from the electronics lab. As fermentation proceeds, the temperature of the grains rises and can kill the mycelium at 43 C or so.

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In 14 or so hours, the grain started smelling like a warm grapefruit and heating. I could see fine strands of developing mycelium through a microscope:

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In 48 hours the grain started yellowing and I could see conidiophores through a microscope – the mould was getting ready to sporulate.

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At this point I took out the tray out of the incubator and refrigerated it, and proceeded to the second stage of fermentation. I left a handful of the grains in the incubator for a few more days, where it proceeded to sporulate and turned dark green.

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Then I mixed steamed peas, koji and salt, ran the mixture through a meat grinder, packed it into sterilised jars and left it in the kitchen. To be updated in a few months.

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