New Koji Spores
Akita Konno: Roots 36
The following is a translation of an article published by the Akita Konno Shoten Co., Ltd, Production Technology Department Laboratory. Akita Konno has been producing Tane-Koji as starter of Aspergillus since 1910. This article details the results of an extensive research project to produce a koji spore that can generate more glucoamylase and less acid carboxypeptidase in a relatively short amount of time (40hrs) rather than the conventional 48 or 50 hrs.
At the end of the article we’ll provide a translation of a table showing enzyme titer data of other spores they offer so you can compare and contrast what will work for you.
Akita Konno typically works with commercial breweries and koji makers because they only sell large quantities of spores and don’t have a “home brew” equivalent. Ultimately, you might end up spending more money than you would if you purchase spores on some of the more convenient websites, but it will be worth every penny if you know basics of koji growing and can achieve reproducible results.
My Professional Experience using Roots 36
I have recently had an opportunity to work with these spores in a professional setting. The spores seemed to have a slower growth initially, but once the koji started generating heat it was a fast climb. Between naka-shigoto and shimai-shigoto was only 2-3 hours. The standard aldehyde aroma appeared during mori as koji was moved from the mountain into boxes, and by shimai-shigoto the aroma was rounding out to a definitive but subtle chestnut.
Speaking with Dr. Hiroshi Konno (President of Akita Konno) after the fact, I suggested the description of the flavor as “mellow”, in addition to the attributes that he accurately described, matching my own experience, and he emphatically agreed with that term. The gentle sweetness, low acidity, and quick growing time give it great promise for Ginjo and Daiginjo applications.
Enzyme analysis results were send to us and yielded incredible figures (U/g Koji・Dry matter):
Our results: GA: 429, αA: 947, P: 1660, AP: 1645, G/α: 0.453
Standard: GA: 350, αA: 873, P: 1672, AP: 3580, G/α: 0.40
My Hope for spores like Roots 36
While the greater sake brewing world will be positively impacted by new spores like Roots 36, my real hope for this engineering marvel is the effect it may have on brewers who cannot access polished rice as easily. All of Europe currently is without a specialized rice polisher for sake and they are not alone. Canada, Mexico, and South America are all home to sake breweries that don’t have easy or affordable access to polished rice.
I believe that with these spores we could see a more refined flavor from minimally polished rice and that could highly benefit the aforementioned brewers in addition to the many home brewers who are just starting out or who have 10 years experience but just can’t refine the flavor any further with the resources they have.
Here you can see a 90% polish sake produced with Roots 36:
Dewa Tsuru Naturally Cultivated Rice Prepared Sasanishiki Kaze no Oto Nama Genshu
The raw rice is T-FARM, grown by Kohei Taguchi, Sasanishiki, which is grown naturally without using fertilizers and pesticides, and is 90% polished, acidity 1.9, amino acids 1.0, sake content -2, alcohol 16.1%. - Hiroshi Akimoto
While we are covering Roots 36 in this article, please also consider the Oriza 1061 which was also release recently. These is a presentation from a recent symposium (in Japanese) that details the differences between these and some of the challenges with releasing a new spore type. In short, it can be quite dangerous because it is possible to accidentally produce a spore which creates aflatoxins, which would be poisonous.
Exciting times ahead! Please read on to hear about the study and the data collected from growing koji and making small ginjo batches to compare flavor and aroma.
Akita Konno Article Translation:
This is the beginning of the Akita Konno document translation.
Original Article (print only):
令和4年度 第68回清酒麹鑑評会
温古知新 (60):2023 p.79-84
The 68th Sake Koji Appraisal Meeting in Reiwa 4
文古知新 (60):2023 p.79-84
The 68th Sake Koji Appraisal Meeting - 2022
Akita Konno Shoten Co., Ltd.
Production Technology Department Labratory
Purpose
At the 68th Sake Kanpeikai in 2022 we conducted a Koji Production Test using our new spores and a small brewing test for ginjo sake using this koji. Roots 36 is Aspergillus Oryzae isolated from made with rice of a sake making grade in Iwate Prefecture by the Iwate Prefectural Industrial Tech Center and is an innovative product that has both “high glucoamylase activity” and “low acid carboxypeptidases (ACP) activity”. Good balance of enzyme titer and a short growing time. Since the GA ration is relatively high it is expected to be used for ginjo sake and daiginjo sake.
At this evaluation meeting we asked participants to evaluate koji made in 35, 40, and 50 hrs in order to see the differences in appearance, aroma, taste, etc. Due to differences in koji making time. We also sampled a batch of ginjo sake produced using koji made under the same conditions and difference in the ratio of koji used with different koji times as well as the balance with the final water ratio of the batch. We received comments regarding the effects of these changes, so we will report them with the details of the test.
Koji Making Test
2-1 Relationship between soaking water absorption rate and retained moisture (moisture content) of polished rice.
Based on our experience, we believe that the standard moisture content of polished rice after soaking for good quality steamed rice is approx. 31.5% for koji rice and 30.5% for kakemai. It has also been confirmed that “raw steaming” occurs when moisture content of polished rice drops below 28.5% after soaking. Therefore, it is necessary to measure the moisture content of polished rice to be used in advance and calculate the appropriate soaking water absorption rate to produce good quality steamed rice. The relationship between immersion water absorption rate , the moisture content of the polished rice, and the moisture content of polished rice after soaking is shown below:
The moisture content of polished rice used in this koji test was 8.2% so in order to ensure an appropriate level of moisture in the polished rice after soaking, the target soaking water absorption rate was set at 34%. The average value of the actually measured immersion water absorption rate was 32.9%
2-2 Roots 36 Koji Making Test
The koji making conditions of the exhibited koji (Table 1), the temperature course during koji making (FIg 1-3), the enzyme titer in the week after making the koji (Table 2), and the comments on the koji immediately after making the koji (Table 3). Enzyme titer was measured according to the National Institute of Alcohol Beverage Standard analytical method (prescribed analytical method by the National Tax Agency) and expressed as a dry matter equivalent value (U/g Koji ・dry matter)
Roots 36 is a koji spore that can obtain sufficient enzyme titer even in a short time, and browning tends to be suppressed if the koji making time is short. In addition, it is a koji spore that is relatively unlikely to produce high amounts of ACP even if the koji making time is extended. As the koji progressed , the temperature of the koji rose to around 40°C from around 35 hours in the koji making period, so the production of glucoamylase and a-amylase tended to increase between 35 and 40 hours. In addition, the ACP was around 3,000 (U/g koji ・dry matter) even after 50 hours, which is low compared to other spores.
In terms of temperature growth, Aspergillus Oryzae is quick and has a high ability to maintain product temperature beyond the maximum temp; It’s easy to ensure sufficient enzyme titer even when making koji for a short period of time.
Comments on the koji in this review show that as the koji making time increases, the quality of the koji improves, but after 35 hours, the koji were evaluated as being young due to the hardness of the koji and the lack of sweetness. Comments after 40 hours were, the taste was well balanced and sweet, and after 50 hours, the aroma was strong and seemed a little too advanced, but it did not feel aged.
Small Ginjo Brew Test
In the small brewery test, we used koji prepared in advance under the same conditions as the exhibited Koji (Table 4). The enzyme titers usd in the Small Brewing Example are shown in table (Table 4). Preparation conditions for the ginjo recipe are shown in tables 5 and 6. Regarding the brewed sake, the most popular comments are summarized in Table 7. Before brewing the target components were set at 15.6% ABV and -3.0 SMV.
(1) As a results of a 15% koji ration, when using 40hr koji, the final water ration is 150%, and when using koji made in 50 hrs the water ration was 165%, comments of the quality of sake made with 40 hr koji was “Beautiful and light in taste”, but “remains bitter”, while the quality of 50-hr koji is “heavy aftertaste” and “slightly acidic”.
(2) Results of preparation with a 20% koji ratio: 40hrs @ 155% water ration, 50hr @ 168% water ration are as follows: In terms of sake comments, the quality of sake made with koji for 40 hours is “strong and full-bodied”, “the taste is crisp and well-balanced”, and the quality of sake made with 50hr koji is “a little heavy in taste”, “bitter and astringent”. Some other comments include, “it leaves a bad taste”
(3) For small batches using 35 hr koji, the koji ratio was set high for 40%, for 40 hrs 20%, and 50 hrs, 15%. The respective water ratios were: 150%, 15%, and 165%.
Comments on the pressed sake indicate the quality of ginjo sake made w/ 35 hr koji is “full flavor” and “good balance between sweetness and acidity” and “beautiful aftertaste”. Ginjo sake made with 50 hr koji included “good balance of sweetness and sourness”, “a bit heavy aftertaste” and “bitterness remains”.
Summary
Roots 36 is suitable for short-time koji making. Looking at the comments, we concluded that the 35hr koji was too young. 40hr koji received good reviews for its firmness, sweetness, and chestnut flavor. In addition, the koji made in 50 hours was evaluated as having a slightly rough texture, but had a strong flavor and a chestnut aroma. Here are comments regarding the small brewing test of ginjo sake using the above mentioned koji:
Small brewing test percentage and quality of sake
As for the 35 hr koji, even if the koji percentage is set to 40% of the total rice, there were negative comments on the taste of the sake. It was evaluated to be “bland and unsatisfying” and “feels astringent”.
For the koji made with 50 hr koji, even when the koji ratio was 15%, comments on the sake produced included “a good balance of sweetness and acidity”, “a somewhat heavy aftertaste”, and “remains bitter and astringent”. As for the magnitude of the effect on the sake quality, the difference in koji quality is more due to the difference in koji making time than the koji ratio.
Final water ratio and alcohol quality of small brewing test
40hr koji was prepared with a ratio of 20% and a final water ratio of 155%.
Comments on the sake made with this recipe was said to have “strong flavor and light”, “the taste is crisp and well-balanced”, but the quality of the 50hr koji was evaluated as “a little heavy” and “astringent”
Regarding the influence on sake quality, it was suggested that the koji making time and sake water ratios were also important.
The results of this test will be used to design future Ginjo sake quality. We hope that you find this helpful as a reference.
This is the end of the Akita Konno document translation.
Appendix
Please refer to the Akita Konno website for more on their Sake Spores.
Koji-Kin Types
As of this publication, the following are available on for purchase:
・For special ginjo sake (特別吟醸用): You can obtain top-quality de-koji with good aroma, color, and simmering of the koji, and a good enzyme balance.
・Gluco S (吟醸用グルコS菌): Spores for Ginjo sake. Takes a longer time, but the glucoamylase content is higher.
・For Ginjo No. 5 (吟醸用No.5菌): you can obtain a pure white and ``full-bodied'' breakthrough-type koji.
・Ice type for Ginjo (吟醸用氷上タイプ): You can obtain dry koji without running out of power even at high temperatures after finishing work.
・N54G bacteria for Ginjo (吟醸用N54G菌): The enzyme production of glucoamylase and α-amylase is well balanced, and there is no shortage of glucose supply in the moromi, creating a good taste with less unpleasant taste.
・Special moromi ginka (patent no. 1500356) (特別醪用吟香): It has a strong leucine acid production ability and produces sake with a harmonious aroma and taste. Suitable for high-grade sake such as pure rice sake and honjozo sake.
・Ginmi (Patent No. 4851481) (吟味): The concentration of fusel alcohol, aromatic alcohol, and arginine, which are related to the taste of sake, is suppressed, resulting in a good aftertaste.
・For Moto (酛立用): Mainly consists of strains that grow aerobically and have strong enzymatic activity, and is characterized by its fast-acting type, strong haze growth, and good Baumé production.
・For Moromi (醪用): This is a seed koji that focuses on aroma and taste for moromi , and is suitable for making clean sake without any habit.
・For Tsukihaze (ツキハゼ菌): We have selected a type of koji mold that is susceptible to tsukihaze, which allows you to get koji that is well-bited and swollen. A thin layer of machine-made koji or lid koji is more effective.
・Soft Konno (ソフトコンノ): For soft connoisseur type mash. It has strong enzymatic power, produces highly economical sake quality, and removes dregs. It is characterized by a pro-relaxed type and high tyrosinase activity.
・Special strain for liquefaction preparation (液化仕込専用菌): strain with strong liquefaction ability, available in rapid type A and slow type B. It is characterized by high tyrosinase activity.
・For non-browning mash (moonlight) (非褐変性醪用月光): tyrosinase activity is low and pure white koji can be obtained.
・Hokuto Zenkyu type for special moromi (特別醪用北斗): has a good aroma, the koji does not brown, and the quality of the sake is light and low in amino acids.
・For Mirin (味醂用): This seed koji has particularly strong amylase titer for mirin , making it easy to create the unique flavor of mirin.
・Non-Producing DF Moonlight No. 5 (DF非生産性月光5号): Prevents sake from coloring due to DF non-productive Gekko No. 5 iron. The color of the sake is less than half that of the control seed koji for moromi.
・IV-2 for Namazake (生酒専用IV-2): This is a seed koji with low productivity of isovaleraldehyde, which is the precursor of the stuffy aroma of Namazake.
・Vintage Yellow Koji Aarburg Strain (復刻黄こうじアールブルグ株): This is a yellow koji mold that was first isolated from rice malt by Mr. Aarburg in Japan in 1899. This is a made-to-order product. *1
*1 Made-to-order products may take more than a month to be delivered, so please contact us for details.
Powdered bacteria for Ginjo are also made to order, so please contact us.
Color Coded Chart of Enzyme Results
Having worked in the UI/UX space for a long time, I learned that we perceive/discern colors much faster than we read. So I have prepared this version of Akita Konno’s koji-kin so you can more easily decide which are better for your purposes.
Below you can see a comparison of all the products listed above, with the Test we performed and the results listed next to the Roots 36: 40hr and 50hr listed values.
Our koji results came back fantastic, showing a nice 1:2 G:A ratio and extremely low AP and ACP. In fact, I had to update the chart with a new blue color just to call out how low they were.
