Koji Comparison

Compared Cold Mountain, GEM Cultures, Home made and SakeOne koji for sweetness, texture and appearance.

I have been thinking about how different koji compare with each other. The most meaningful way would be to compare sake made from each. However, I can’t do this at this time so I decided to look at the koji itself. The koji I looked at are: Cold Mountain, GEM Cultures, home made koji from GEM Cultures’ Koji-kin and SakeOne koji.

Both the Cold Mountain and GEM Cultures koji are quite dry and hard. When bit they are a little softer than dry rice but not by much. The home made and SakeOne koji are “fresher” and somewhat soft and chewy.

Cold Mountain and GEM Cultures seem less sweet than SakeOne which much less sweet then the home make koji. Given the minimal fuzz covering of the home made koji, I was surprised it was by far the sweetest. This seems to indicate a healthy amount of enzyme despite the lack of fuzz. To check to see how much the dryness is effecting the sweetness, I soaked some koji from each sample.

After soaking for an hour the water for Cold Mountain and GEM Cultures were a little sweet. The water for the home made koji was almost like syrup. However, the water for SakeOne was the least sweet. As for the koji itself, Cold Mountain was now the sweetest. GEM Cultures koji was noticeably sweeter but has a strong brand taste. Neither the SakeOne nor the home made koji seemed sweet any longer.

Four Kojis: Cold Mountain, GEM Cultures, Home Made, SakeOne
Four Kojis: Cold Mountain, GEM Cultures, Home Made, SakeOne

There is a clear difference in the look between each of these koji. The two lightest are on either end in the picture; the lightest being the SakeOne koji which looks like most of the pictures of what koji is supposed to look like. The Cold Mountain koji is slightly darker and has the smallest granuals.

Cold Mountain Koji
Cold Mountain Koji

The GEM Cultures koji is the darkest of all the koji. It may have been made with brown rice but I don’t know.

GEM Cultures Koji
GEM Cultures Koji

I made the home made koji with GEM Cultures koji-kin. I also tried making koji from Vision Brewings koji-kin but I screwed it up. I used rice milled to 60% for this koji but it is darker than I think it should be and it did not get a full fuzzy covering; a few grains only.

Home Made  Koji from GEM Cultures' koji-kin
Home Made Koji from GEM Cultures' koji-kin

SakeOne’s koji is a beautiful bright white, looking as it is supposed to look.

SakeOne koji made from rice milled to 60%.
SakeOne koji made from rice milled to 60%.

It is interesting that the koji-kin from GEM Cultures and Vision Brewing are different colors: GEM Cultures’ is army green while Vision Brewing’s is bright white.

GEM Cultures' Koji-kin.
GEM Cultures' Koji-kin.
Vision Brewing's Koji-kin.
Vision Brewing's Koji-kin.

I would like to update this article when I get a chance by adding home make koji from Vision Brewings koji-kin.

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7 thoughts on “Koji Comparison”

  1. Taylor made AK is right about the color difference in older kojikin but also some companies in an effort to increase $$$$$ instead of shaking or harvesting the kojikin from the rice kernel they just blend the whole thing up adding the weight of the rice with the kojikin. They figure nobody would know the difference.

  2. Hi Will,

    Great study. Would you be able to answer a question please? I tried the Vision koji on sweet rice (~85F/40hr). It did have a nutty odor but no taste. After fermentation (Farmhouse sake recipe @ 16% alc), it did not have much alcohol. The fermentation was slow for the 10 days and was clearly done at that time. Taste is okay…but there seems to be little alcohol content. Should I assume the koji did not grow? Thanks, Rene

    1. Rene,

      I can’t really tell from this. Clearly the koji was doing something if you get a nutty odor. Did you see the mold covering the rice, completely or in part?

      A good way to test koji is to make amazake with it, or some of it. To do this you can combine freshly steamed rice (140F or so) with koji. and keep warm for about 6 hours. This should produce a very sweet rice porridge; use maybe 1/3 koji to 2/3 rice.

      A couple of articles that might help are: Amazake – it ain’t sake and Making Koji for Sake.

      Keep in touch

  3. Will,
    Thanks so much for the prompt answer!
    I will give Amazake a try! I was not familiar with it, but looked it up on wikipedia. Sounds like it would make a great addition to my morning smoothie, and testing my koji this way seems like a much better idea than my plan to just go ahead with this, my first batch of sake and hope that it works. There is such a dearth of good info on sake brewing on the webs – thanks for your excellent and informative website. I hope that sake homebrewing takes off in this country, and that your online shop takes off!
    Regards,
    Rob

  4. Will,
    I’m at the beginning stage of my first attempt to homebrew sake, and I’m stuck and wonder if you can help me…
    I washed, soaked, steamed, cooled, dusted and incubated 3.5 cups of Koda Farms Sho-Chiku-Bai rice with spores from Vision Brewing as per Bob Taylor’s excellent guide. The temperature in my ice chest stayed in the 90-96 degree range for the full 48 hours, but I never got any sulfur smell like the rotten eggs that Mr. Taylor describes. Nor is every grain covered with white fuzz. In fact, it came out looking very much like your home made koji sample shown above. It does smell nutty and tastes very sweet, so I guess the enzymes are doing their thing? I guess my question is this: Have you had good results with home made koji as shown above?
    Thanks,
    -Rob

    1. Rob,

      No worries. Good koji does not have to have mold that fully covers the rice. In fact, the type of koji used for the highest grade sakes generally only have the rice about half covered. The important thing is that the mold has worked its way deep into the rice. If it makes it half way to the center, you are doing good. Don’t worry about the lack of a sulfur smell.

      If you would like to test the koji, you can use it to make amazake. If the amazake turns out very sweet and a sticky mash the koji is good.

      Bob’s guide is excellent. Some additional koji making information is here.

      Thanks,

  5. The reason for the color difference between the Vision and GEM spores is simple: koji spores lose their color over time. That’s one of the defining characteristics of this particular strain of aspergillus mold. Your GEM spores were harvested more recently than the Vision spores, that’s all.

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