October 6, 2011

Microbes in your nukadoko/ぬか床の中の微生物たち

When you keep your nukadoko, it is very important to keep in mind the characteristics of the microbes you want to grow in it, as well as those of the ones you don't want to.

Here is a summary.

1. Vegetable lactic acid bacteria
Facultative anaerobic, meaning that they like an environment with a little oxygen.
Can survive in high salt concentration, unlike animal lactic acid bacteria.
Eat sugar to produce lactic acid and amino acid.

2. Yeast
Facultative anaerobic, meaning that it likes an environment with a little oxygen.
Eats sugar to produce alcohol, among others.
Ester is produced from alcohol, giving aroma to nukazuke.

3. Butyric acid bacteria
Obligate anaerobic, meaning that they absolutely hate oxygen.
Unwanted but harmless (used in some antiflatulents).
If you fail to mix your nukadoko regularly, butyric acid bacteria will start growing at the bottom of your nukadoko, giving off the smell of damp socks.

4. Film yeast
Obligate aerobic, meaning that it absolutely likes oxygen.
Unwanted but harmless (used in the production of sherry)
If you fail to mix your nukadoko regularly, film yeast will start growing on the surface of your nukadoko, producing ethyl acetate (thereby giving off a smell like paint thinner).
When mixed inside your nukakodo, it will start alcohol fermentation.

5. Other unwanted bacteria and fungi
Most of them are obligate anaerobic, meaning that they absolutely hate oxygen.
If you fail to mix your nukadoko regularly, you may let butyric acid bacteria to grow, possibly enabling other unwanted bacteria and fungi to grow. If this happens, it will be difficult to recover your nukadoko.



1. 植物性乳酸菌

2. 酵母

3. 酪酸菌

4. 産膜酵母

5. 他の雑菌、かび

(Japanese only)


muskratbyte said...

Very Helpful! Thank you!

Hiroyuki said...

muskrat: Are you ready to start?

I recommend not adding yogurt, bread, or other "contaminants".

Yogurt contains animal lactic acid bacteria, which are not resistant to salt.
And, I found this paper last night:
Bread has no favorable effect on nukadoko.

muskratbyte said...

Yes, I'm on vacation next week... the last time I made nukadoko, I didn't use bread, beer, yogurt or any of the other commonly recommended 'starters'. I just toasted the nuka, added dried peppers, garlic, kombu, a little bonito, and some well cooked, ground eggshell. Any suggestions on these ingredients?

Hiroyuki said...

muskrat: I think that roasted rice bran, water, and salt are the only indispensable ingredients for nukadoko. Red peppers and kombu are well-tried ingredients, so I added them to my nukadoko.

I personaly refrain from adding anything of animal origin, such as dried bonito shavings. Don't ask me why; I just don't want to add them.

Eggshell is often used to recover overly fermented, sour nukadoko, because the calcium in the eggshell will neutralize the acidity (karashi (Japanese mustard) powder is also often used), but I don't think it's used to start nukadoko.

muskratbyte said...

Thanks - I'd read that the egg shells add calcium to the pickle.

Sissi said...

Thank you for such an informative and detailed post. Your blog becomes a nukadoko bible :-)

Hiroyuki said...

Siss: Thanks for your compliment.

I updated a previous post on nukadoko:

I refrained from posting about the carrot nukazuke because that would be quite redundant. The carrot nukazuke was tasty enough, so was the daikon nukazuke. My nukadoko is in good condition.