Junmai sake’s four main ingredients are rice, water, yeast and koji.  With only four ingredients, each is very important to sake’s quality, taste, and aroma.  The sake master brewer also makes decisions that impart flavor characteristics such as milling, choice of yeast, and aging.

Rice plays a critical role in sake’s flavor.  Developed specifically for brewing, sake rice typically has more starch and a harder kernel compared to table rice.  Rice grown in cooler regions has less protein and fat which produces a lighter and more elegant style sake.  Warmer regions in the south of Japan result in a heavier style sake.  For example, AN Tokubetsu Junmai Sake is a rich and complex sake made with Omachi rice from the Okayama Prefecture south of Osaka.  An heirloom variety, Omachi is Japan’s oldest sake rice and is mainly grown in Okayama.  IMA, an innovative sake by Imayo Tsukasa, is made in Niigata in Northwestern Japan.  Niigata is celebrated for its elegant sake and IMA, with its crispness of green apple and tanginess of apricot, is a terrific example.  

Water heavily influences sake’s mouthfeel.  Hard water produces full bodied sakes, while soft water yields a light and delicate sake.  All sake by Imayo Tsukasa is finished with super soft Artesian water sourced from the snowmelt of the nearby Suganadake Mountain.  World renowned for its purity, water from this mountain is brought to the brewery to enhance the delicate flavor profile of his sake.

Yeast contributes to the highly aromatic notes of tropical fruits, savoriness, and high levels of citric acid or lactic acid in sake.  Hirai Junmai by Koshi Tsukano uses a combination of yeast #9, prized for its fragrant aromatics, and a wild yeast called Tsukano Yeast.  Wild yeast is less commonly used because its ability to make alcohol is less dependable.  Breweries willing to take the risk are rewarded with very interesting and unique flavors and aromas.

Sake’s fourth ingredient is koji.  Koji plays an important role in determining sake’s umami flavor.  The higher the ratio of koji to steamed rice, the more umami the sake will have.  Imayo Tsukasa’s Junmai Black Extra Dry is full of unami flavor.

A key ingredient in many fermented foods like miso and soy sauce, koji is a beneficial mold that converts starch and proteins into fermentable sugar.  After the sake rice is steamed, it is spread out by hand and kneaded on a cloth-covered board to cool.  After cooling, the koji spores are sprinkled on the rice.  After 40-50 hours, spores growing on steamed rice start breaking down the starch and the fermentation process has begun.  Fermentation can take 20 – 30 days. 

The rice polishing ratio determines the Junmai’s style and category.  If more of the outer layer of the kernel remains, expect a robust sake with more flavor variations.  If more polishing takes place, expect the pure flavor of the rice to show through because only the heart of the rice remains (shinpaku).  With less than 70% of original rice grain remaining (30% removed), a Junmai sake commands a lower price point.  A Junmai Ginjo has less than 60% remaining.  A Junmai Daiginjo, which tops the pricing scale, has less than 50% of the rice grain remaining.  KOI by Imayo Tsukasa is a Junmai Daiginjo Genshu, a select cuvee of top lots, with beautiful aromatics and a hint of cocoa in the finish.

The next time you take a sip of sake, I hope this post helps you identify and appreciate its flavor nuances.