What to look for in koji

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Making koji for specific purpose - What to look for in koji

Commercially available rice koji might look all same in appearance, but the enzyme balance in them could be very different depending on how they were grown in their 48 hours growing cycle. And this is what it matters most in traditional Japanese fermentation. And this also is the very reason why the quality of koji is regarded as the utmost important factor because the balance and volume of the enzymes determine the taste and flavour of the final ferments. If you have chance to visit Japanese breweries, you would be surprised to find that the final state of koji in sake breweries (very spotty) and those in miso breweries (very fluffy) are very different because of the difference in temperature and humidity control.

I find it fascinating that our Japanese ancestors mastered the skill of making optimum koji for specific purpose (sake, miso, soy sauce etc) long before the modern age. They had no objective means to measure the subtle change in temperature and humidity as no thermometers nor hygrometers were available. They didn’t know the microbes exist, let alone what they are and what they do. I believe our just felt the presence of something awe and respected and humbly communicated with this “something” by deploying all the senses they have. These sincere observations have led to the development of many fine fermentation systems, such as Kimoto.  Kimoto is a sake brewing method accomplished about 400 years ago and is regarded as the finest controlling system of extremely complicated microbial activity, even in the light of current standard. It is truely amazing these were possible without the aid of modern technologies. Our Japanese culture owe them so much.

Making koji for sake

    I am making koji for sake here. The picture above was taken just before the completion.

    Koji doesn’t necessarily look fluffy. Neither it has to form dense mat. Koji tends to become fluffy when the humidity in chamber is high (because they try to grow their mycelium around the grain). Although koji requires certain level of humidity to grow, moisture level higher than necessary would attracts some unwanted microbes, including yeast and lactic acid bacteria, which make the fermentation later on too complicated and difficult to control. I intentionally made chamber drier because I wanted koji to be dominant so that the taste of my sake will be clean.

    There is another reason why I made the humidity low. I wanted to encourage the growth inside the grain. Inner rice is more starch-oriented and when mycelium grow here, it produces much-needed amylase in sake application. I am chuffed that the entire cross-section of rice is mat white, meaning mycelium well grew inside.
Can’t wait brewing doburoku with this koji.

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