Hishiroku Kyoto: Japan's Oldest Koji Merchant
Not too long ago, a friend gave me a packet of a product I hadn’t seen before, Hishiroku koji rice powder. It has the consistency of fine rice flour but packs the transformative power of koji. I tried using it in various cooking and baking experiments (pancakes, marinades, pickled vegetables, hamburg steak and tomato sauce) and found that in addition to aiding in fermentation, it added texture and umami to foods.
The term “koji” can refer to the mold-inoculated rice that transforms rice starch into fermentable sugars in the sake-making process. It’s also used to refer to the mold itself. But koji-kin is the more specific term for the invisible, long-armed Aspergillus oryzae spores that have been used for millennia in Asia to brew sake and other drinks.
Koji merchants cultivate pure, stabilized strains of dozens of different type of seed koji by propagating them on a substrate of rice or barley. In addition to sake brewers, they sell their products to makers of fermented products ranging from soy sauce, mirin, and shochu to the Okinawan drink awamori.
Our book research led to visits with several companies that cultivate koji-kin. They are a hidden yet fascinating part of sake culture, so I’m looking forward to sharing that information with you when our book comes out next spring.
I knew that Hishiroku is the oldest of the six or so commercial koji merchants still doing business in Japan today, and has been in business for more than 300 years. But to learn more about the company, which is located in the Higashiyama district of Kyoto, I reached out to president Akihiko Sukeno.
He told me that he can trace his lineage back to his great-great grandfather, but beyond that records are murky. Family lore has it that the roots of the business stretch back to the Saikyo koji-za guild, which was housed on the grounds of Kyoto’s more than 1,000-year-old Kitano Tenmangu Temple.
We know from written records that in Japan the commercial cultivation of koji mold dates back to at least the eighth century. In the middle ages the temple-affiliated koji-za guild held the exclusive right to cultivate koji spores. For the ruling shogunate, controlling the guild was a way of controlling and maximizing tax revenues from alcohol sales. But enterprising sake brewers began to think they could do better, and started growing their own in-house molds. Competing commercial breeders also arrived on the scene.
The situation was ripe for a clash, which is exactly what happened in the mid-1400s when worked-up sake makers faced off again the guild, resulting in a giant fire at Kyoto’s Tenmangu shrine—the same one that Hishiroku traces its roots back to—and the deaths of dozens of people.
Some of the many different koji-kin strains Hishiroku customers can order. Photo courtesy of Hishiroku.
Today Hishiroku serves about 2,000 client companies, and offers roughly 50 different strains of koji-kin. You can also buy retail products at the Hishiroku office in Higashiyama. The strain of koji-kin that a brewer opts for in a sake depends on the profile that he or she is going for; each results in a different combination and ratio of aroma-producing enzymes. Selecting the right strain can be compared to selecting different strains of mold used to inoculate surface-ripened cheeses like Camembert or Comté in order to produce the desired tastes and aromas.
Although he can’t talk much about the ancient history of the company, Sukeno does know that during World War II, when food shortages threatened the lives of millions of Japanese, the business struggled. The government had seized control of the nation’s rice supplies, which were directed to the military first before they could be made available to food sellers. Ordinary citizens lived on the verge of starvation and white rice became such a scarce and valued commodity it became known as “silver” rice. I remember one of my relatives describing to me how during the war starving citizens would go into the mountains to forage for whatever foodstuff they could find.
It was under these harsh conditions that Sukeno’s grandmother was arrested during the war. Since Hishiroku used rice as a raw material for cultivating koji-kin, Sukeno explains, “It seems she was arrested and put in jail on suspicion of diverting it to be sold on the black market for food.” Koji-kin was still needed because certain sake makers were allowed to continue to brew sake despite the rice shortages. The reason: soldiers needed their sake, though the wartime version was so notoriously diluted that it became derisively known among the troops as “goldfish water.”
I wondered if the western craze for fermented foods, and making everything from sourdough bread to kombucha was a thing in Japan. Sukeno did tell me that the second most popular product he sells after the koji-kin itself is koji rice. Sometimes described in English as “malted rice,” it’s actually dried koji-inoculated rice that you can use to make the versatile condiment shio-koji or the sweet drink amazake. He adds, “There’s been a boom in the use of shio-koji and amazake, so sales may have increased a bit, but if so, only slightly.”
As for the koji rice powder that initially brought me to him, Sukeno says that it has been available for sale since 2017. Sales do not extend to North America, though I did see it advertised on eBay for 25 USD per pack, quite a mark-up from 500 yen (under 5 USD) list price. The most popular use of koji rice powder among home cooks is as an additive to shokupan, the beloved white milk bread of Japan. The koji powder helps make it moist and fluffy. Sukeno himself likes to add the koji rice powder to miso soup and dashiyaki tamago (dashi-flavored rolled egg omelet) batter. In the former, he explains, it aids in digestion, and in the latter, it helps make the texture of the egg roll firmer. I’m going to try adding it to those next!
Please let me know if you have tried koji rice powder or dried koji rice and some of your favorite ways to use them.
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