adding in yoghurt cultures?
also temperature experimentation to try to select for different types of lacto-bacteria
Notes and Observations
After three days of curing in the renan wheat shio koji, the tofu became completely soft, intensely sour, and quite salty. It is very flavorful, though very overpowering when eaten on its own.
Compared to previous trials, which yielded a profile that was quite cheesy, this batch is much more lactic and sour, which may be a result of the type of koji used, as we’ve observed rice koji tends to produce cheesier shio koji.
- Duration: A shorter cure, perhaps just overnight, would likely yield a more cheesy profile.
- Alternative Method: Fermenting the koji directly alongside the tofu (rather than using a prepared shio koji) might produce a much milder, less sour tofu cheese.
We’ve noticed that when using rice koji, you get a more cheese-like flavor - the fermenting rice koji has a cheddar like sharpness and funk, while the other shio kojis seem to be — not necessarily more neutral — but more of a koji funky acidity — that being said, it’s worthing testing how each of these cures soy curd to form something cheese like
NEW EXPERIMENT
(1) tofu in three shio koji (wheat, sorghum, rice) tofu with rice koji, oat koji, and rye koji overnight tofu with rice koji, yoghurt culture, high temp (same ratios)
50g tofu for each (150g for the last one), and 10g koji, 2.5% salt, enough water to cover (100g), small pinch (.2g) of vegan yoghurt starter) and fermented at 105
control (1) smoked dried hot dried cold dried
(1) parmesan blend, fermented then dried (450g tofu, 50g koji, 2% salt, 50g lacto-ferment brine (in this case from lacto-fermnted wheat) ) half fermented in the fridge, in cheese cloth over a grate to dry half fermented out of fridge, in a container
rice koji overnight has a pleasant loight umaminesss and slight cheesiness, could be done with larger pieces
rye one is just weirdly sour, not super umami, odd
ost one pretty umami, slight odd flavor, like the rice but less neutral
rice shio koji marinated in fridge, less cheesy, more round with less acidity,plesatnbut much more similar (predictably) to something you’d get at like aedan and its in a bento
sorghum one similar with a slgith funk at end
wheat more flavorfulm, maybe slight cheesiness but also a bit plasticy and funky
Research
Why shio-koji tofu can read as cheese-like
The analogy is chemically plausible, but it is closest to a young bloomy-rind cheese rather than a blue cheese. Koji and cheese can arrive at several of the same aroma compounds by different routes, while shio koji’s proteases can turn tofu’s soy protein into peptides and free amino acids in a way that resembles the proteolysis of casein during cheese ripening.
- Mushroom / mold-rind: Sake koji contains the fungal C8 odorants 1-octen-3-one and 1-octen-3-ol. A GC-olfactometry study found both, and found more of them in strongly aromatic koji; 1-octen-3-one was among the highest-impact odorants. The same two compounds are potent odorants in Camembert. This is the clearest direct aroma overlap between koji and bloomy-rind cheese. (Takahashi et al., 2006; Kubíčková and Grosch, 1998)
- Malty / nutty / aged: Koji fermentation can produce the branched aldehydes 2-methylpropanal, 2-methylbutanal, and 3-methylbutanal. The latter two were already present during soy-sauce koji making. Cheese microbes also make branched aldehydes from amino acids; 3-methylbutanal is an established flavor compound in many hard and semi-hard cheeses. (Feng et al., 2013; Afzal et al., 2017)
- Savory / cooked-potato / sulfurous: Koji aroma contains methional, a methionine-derived, cooked-potato-like odorant. Methional is also a key Camembert odorant and occurs among the key odorants of ripened Cheddar. Camembert additionally relies on methanethiol and dimethyl sulfide for sulfurous/garlic character, but their presence should not be assumed in this tofu without analysis. (Takahashi et al., 2006; Wang et al., 2021)
- Butter / cultured dairy: Acetoin and, depending on strain, diacetyl can occur in koji-ripened dairy cheese. Diacetyl is also one of Camembert’s potent odorants. This supports a buttery association, but evidence for either compound specifically in rice shio koji or shio-koji-cured tofu is still indirect. (Tomita et al., 2022; Kubíčková and Grosch, 1998)
- Sharp / sweaty / “cheesy”: Butanoic and isovaleric acids are potent Camembert odorants. Koji systems can contain the same or related short-chain acids, but organism and substrate matter: their detection in a mixed or soybean-koji system does not prove that A. oryzae made them in rice shio koji. In tofu, this part of the aroma could come from the shio koji, secondary salt-tolerant microbes, or lipid breakdown.
What the direct koji-cheese research shows
Tomita and colleagues surface-ripened dairy cheese with five strains of Aspergillus oryzae or A. sojae. Compared with Camembert, Brie, and blue cheese, these koji cheeses had higher amino-acid and acetoin levels, rapid accumulation of glutamate, aspartate, 3-methylbutanal, and 3-methylbutanoic acid, and lower methyl-ketone and volatile-fatty-acid levels. A companion study found similar or greater surface protease activity than Penicillium, but highly strain-dependent lipase activity. (Tomita et al., 2022; Suzuki et al., 2021)
This suggests the most useful model for tofu:
Koji resembles cheese ripening most strongly through protein breakdown and amino-acid-derived flavor, and usually less through the milk-fat chemistry that defines blue and strongly lipolysed cheeses.
Tofu supplies abundant protein but not casein, and its fat differs from milk fat. It can therefore develop softness, savoriness, and aged/malty aromas without reproducing dairy cheese exactly. Classic blue-cheese methyl ketones such as 2-heptanone and 2-nonanone are particularly unlikely to dominate unless a suitable mold and fat substrate are present. Conversely, a very lipolytic A. oryzae strain can release enough volatile fatty acids from dairy curd to cause rancidity, so the result is strongly strain- and substrate-dependent. (Chintagavongse et al., 2024)
Interpretation of this trial
- The complete softening is consistent with continued proteolysis, although salt, acidity, and the tofu’s starting structure could also contribute. Softness alone does not demonstrate a particular cheese-ripening pathway.
- The strong sourness should not automatically be called “lactic” without pH, titratable-acidity, or microbial data. Commercial/traditional shio koji is a salted enzyme preparation with a potentially variable accompanying microbiota; sourness could reflect organic-acid accumulation by secondary microbes rather than A. oryzae itself.
- The hypothesis that a shorter cure tastes cheesier is reasonable as a sensory hypothesis: it may preserve the koji’s mushroom, malty, and nutty top notes before salt, acid, and extensive proteolysis dominate. It is not yet established by the cited literature and should be tested directly.
- Salt changes aroma formation, not merely aroma release. In one salted-koji study, adding salt after amazake digestion did not reproduce the odor of koji salted from the beginning. The individual responsible compounds were not established, so this does not by itself explain the difference between rice and wheat shio koji. (Hasegawa and Funakoshi, 2015)
Next comparison
Run the rice and wheat shio koji side by side on pieces cut from the same tofu block. Keep shio-koji dose, cure temperature, and tofu thickness constant, and taste at 12, 24, 48, and 72 hours. Record pH, saltiness, sourness, mushroom/mold-rind aroma, malty/nutty aroma, buttery aroma, sulfur/funk, bitterness, umami, and softness. An enzyme-inactivated shio-koji control would help distinguish aromas carried in by the condiment from flavors generated by its enzymes during the cure.