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Tippsy Sake Guide

Lesson 2: What Is Sake Made of and How Is It Made?

Now that we’ve begun to answer the question “what is sake?” in the previous lesson, are you ready to learn what sake is made of? This article covers the primary ingredients of this ancient Japanese beverage.

What is sake made of? 4 key ingredients

Sake only has a handful of ingredients. Rice is the most well-known of these, but it won’t ferment on its own. Water, koji and yeast are essential to turn rice into sake.

Quality water is the backbone of every sake brewery, and each source has a unique profile that affects the aroma, flavor and texture of sake.

Koji is sake’s secret weapon: it turns starchy rice into sugar that is fermentable.

And finally, yeast is an ingredient in all alcoholic beverages, including sake. Koji gives it sugar, and yeast turns it into alcohol

First, let’s look closer at sake’s most famous ingredient. 

Key ingredient #1: Sake rice

Samples of Yamadanishiki

A verdant field of sake rice.

“Sakamai” is a broad term for “sake rice.” It’s almost always short-grain Japonica. Sakamai has two distinct categories: table rice and “shuzokotekimai,” or rice suitable for sake brewing.

Table rice is the stuff we eat. A lot of it is grown in Japan, and it’s affordable. But brewers prefer to use the other type which is used exclusively for sake. That’s because shuzokotekimai has bigger grains, less protein and a sizable starchy core (“shimpaku”). But specialty sake rice is hard to grow. Most varietals are tall, top-heavy and vulnerable to strong winds. And once a plant is knocked over (lodged), it can't be saved. Because of this, shuzokotekimai is expensive.

Types of sake rice

Let’s explore some of the most popular sake rice types. 

Yamadanishiki is the most famous. By volume, it dominates specialty sake rice production. It has big starchy grains, is predictable in the brewery and mills easily without breaking. Yamadanishiki is often used for fruity, fragrant daiginjo and junmai daiginjo.

Sake made with Yamadanishiki rice:

Gohyakumangoku is a Niigata native and number two in shuzukotekimai production volume. It’s a shorter plant than Yamadanishiki and easier to grow. It has smaller grains but large shimpaku, so brewers like it. Gohyakumangoku sake is often light bodied, smooth and mellow. 

Sake made with Gohyakumangoku rice:

Omachi is an heirloom strain of sake rice. It’s an ancestor of many popular sakamai like Yamadanishiki and Gohyakumangoku. Omachi is hard to grow and is mostly restricted to sheltered sites in Okayama. It has large, starchy grains but breaks easily, so it’s rarely milled below 50%. Most Omachi sake is junmai or junmai ginjo. And while it can make fruity sake, it’s beloved for its savory and herbal notes. 

Sake made with Omachi rice:

In Northern Japan, Miyamanishiki is a popular cool-climate sake rice. It tends to make rice-flavored, mellow sake, and it’s pretty easy to grow too. But many brewers have shifted towards newer, locally adapted varieties of rice. Akita Sake Komachi is one such rice. It’s wildly popular in Akita, and it often yields fruity, faintly sweet sake. 

Sake made with Miyamanishiki rice:

Sake made with Akita Sake Komachi rice:

Other major sake rice types to look out for include Dewasansan, Hattannishiki, Tamasakae and Wataribune. 

What is rice polishing?

Rice polishing

Brewers don’t use unmilled rice because the outside of the grain isn't as desirable as the starchy core, so rice is polished or milled to remove the outer parts. In general, highly polished rice makes lighter, fruitier and smoother sake. Conversely, lightly milled rice makes fuller-bodied sake with more umami. 

The amount of rice remaining after polishing is called the “seimaibuai” and is expressed as a percentage, also known as the rice polishing ratio. The premium sake grades have minimum required seimaibuai rates. For honjozo it’s 70%, junmai ginjo/ginjo are 60%, and junmai daiginjo/daiginjo are 50%. Junmai has no minimum seimaibuai, but it’s often around 70%. It’s a bit technical but worth remembering. Sake labels often list the seimaibuai giving you a clue about the sake’s flavor profile. Check out our blog to learn more about the factors that affect what sake tastes like.

Key ingredient #2: Water

Water makes up about 80%-85% of sake’s volume and affects the flavor and texture of sake. This happens directly, with the water contributing to mouthfeel and flavor. Additionally, minerals and nutrients within water impact the brewing process and the organisms responsible for fermentation.

Japanese water is relatively soft, but there’s still a wide range of water hardness from one brewery to the next. Water hardness is an important variable in sake, so let’s dive deeper.

Hard water vs. soft water

Water hardness is the concentration of dissolved minerals. Mineral-rich water is considered hard or “kosui.” Water with fewer minerals is considered soft or “nansui.” Hard water promotes an intense, rapid sake fermentation, which often produces full-bodied, savory sake. Soft water requires a slower fermentation and yields fruity and floral notes. 

With the exception of “genshu” (undiluted sake), water is added to sake before it’s bottled. Hard water adds a firm texture and mineral taste, whereas soft water is silkier and more mild. 

Sake brewing centers like Nada and Fushimi usually develop near famous water sources. Let’s explore this further.

What is Miyamizu? Japan’s famous water sources

Samples of Yamadanishiki

Water rushes over rock at a natural water source.

Miyamizu from the Nada brewing region is one of the most famous waters in Japan. It's hard and often makes dry, savory and fresh sake. 

Miyamizu / Nada sake:

Fushimi, Kyoto, also became famous because of its medium-hard spring water called Fushimizu. Compared to Nada, the sake from Fushimi tends to be silkier, fruitier and a little sweeter. 

Fushimi sake:

Saijo, Hiroshima, is where brewers learned how to make sake with soft water. The techniques developed in Saijo led to the creation of fruity ginjo sake. Snowy Niigata also has softer water. Brewers there use it to produce the region’s light and dry style. 

Saijo sake:

Niigata sake:

Key ingredient #3: Koji

Samples of Yamadanishiki

Rice inoculated with yellow koji mold.

Koji is a critically important sake ingredient. Without it, sake rice wouldn’t be fermentable. It’s also a key ingredient in many other Japanese food products like miso, soy sauce and mirin.

What is koji?

Koji is a fungus that grows naturally on rice. There are several types of koji, but sake brewers traditionally use yellow koji. When sake rice is inoculated with koji spores, the fungus will convert the grain’s starch into fermentable sugars. 

Making koji rice is a critical step in the sake brewing process. How the koji is allowed to develop onto the rice will affect the fermentation and resulting sake. When koji mold covers the surface and much of the core, it can make full-bodied sake. But when koji only sparsely covers the outside, it’s better for fruity and elegant sake. 

 Key ingredient #4: Yeast

Yeast is possibly man’s best friend. This single-celled fungus converts sugar into alcohol. Without yeast, there would be no sake. 

Sake yeast, or Saccharomyces cerevisiae, is the same species used in beer brewing and baking. However, sake uses unique varieties of fermentation yeast. Let’s look at some of the most important.

Types of yeast

Many sake yeast types are available to brewers — each with its own character. The most popular sake yeast is No. 7. It yields a mellow, fruity sake with a subdued aroma. But yeast No. 7 isn't generally used for premium ginjo sake. For that, No. 9 is the most common. It makes aromatic, floral and fruity sake with a crisp finish. 

Sake made with No.7 yeast:

Sake made with No. 9 yeast:

Another popular strain for aromatic, fruity and soft sake is No. 10. It ferments well at low temperatures, making it perfect for brewing premium ginjo sake. 

Sake made with No. 10, No. 1001 yeast:

Finally, many popular yeasts have foamless variations. They have the suffix “-01.” For example, No. 9’s foamless form is No. 901. Yeast No. 1801 is a popular foamless strain, and it produces extremely juicy, low-acid sake. 

Sake made with No. 1801 yeast:

  Additional sake ingredients

Rice, koji, yeast and water are the four main sake ingredients. But there are a couple of additional ingredients that play a part. 

 Lactic acid

Lactic acid is an organic acid and a critical component in still-developing sake. It’s either added directly or cultivated naturally. What is lactic acid used for? It inhibits unwanted bacteria from spoiling the sake.

Hundreds of years ago, kimoto sake was developed to fight off spoilage. Cold temperatures and physical mash-mixing allow ambient lactic acid bacteria transfers to the mash. Yamahai sake is comparatively new, but it achieves the same thing: savory, tart sake. 

Kimoto sake examples:

Yamahai sake examples:

Today, most sake has lactic acid added directly to the mash. Called “sokujo-moto,” meaning “fast-brewing yeast starter,” it’s reliable and makes clean-flavored sake. But the term won’t appear on a label.

Brewer’s alcohol

A small amount of distilled alcohol is permitted and serves several purposes. It extracts esters and other aroma ingredients, producing more aromatic intensity. It also dilutes flavors derived from rice and fermentation, making sake taste lighter. Other reasons alcohol is added include spoilage resistance and increased yield of lower-grade sake. 

By volume, the majority of sake today includes brewer's alcohol. Most of the volume is “futsushu,” which means “ordinary sake” (table sake), but daiginjo, ginjo and honjozo sake contain it too. Only a little is permitted: less than 10% of the weight of the rice. 

These three premium sake grades are just as tasty and complex as their junmai counterparts. The added alcohol just makes them a bit more aromatic and light.

Sugar and other additives

What’s the difference between table sake and premium sake? Well, premium sake has more restrictive ingredient requirements. With futsushu, adding sugar, organic acids, amino-acid salts and shochu is allowed. Futsushu also doesn’t have rice milling requirements, whereas premium sake — other than junmai — must use rice with a seimaibuai of at least 70%. An excellent example of futsushu sake is Hakutsuru “Brewer’s Pride.”

The building blocks of sake

Hopefully, you find this deep dive into sake ingredients helpful. Understanding how rice polishing affects flavor, for example, is an easy win. The rest may take time and tasting, but the suggested brands will give you a head start. 

Now that you know about the building blocks of sake, let’s take a look at how these ingredients fit into the brewing process.

How is sake made? The complete sake brewing processes

Samples of Yamadanishiki

Brewery workers at Tomita Brewing Company mix and prepare the yeast starter.  Courtesy of Tomita Brewing Company.

Sake brewing has been going on for millennia. Rice arrived in Japan around the third century B.C., and a crude version of sake appeared shortly thereafter.

Over the centuries, sake brewing has evolved and become quite sophisticated. And while there is a general method for making sake, choices made during each step can affect its flavor dramatically. This article breaks down the steps of sake brewing and why each is important. 

Polishing rice

As discussed earlier, sake brewing starts with brown rice, but that won’t make great sake easily as is. Most of the protein, minerals and fat are on the outside of the rice, and these components are undesirable in large quantities. What is desirable for brewing is the starchy core (shimpaku) in the center. So to make quality sake, it’s important to polish away some of the outside. Rice is rested after polishing for up to a month to dry out. 

Washing and soaking rice

With the resting phase over, it’s time to start making sake! The first act is to wash the milled rice. Washing rice removes the bran and other particles left over from milling. 

After washing, the rice is soaked to absorb water. It’s extremely important to get this step right. Over-soaking leads to rice that’s too soft after steaming, while under-soaking leaves the rice too hard. Both make it difficult for koji to grow. For ginjoshu (junmai ginjo, daiginjo, etc.), soaking is often done by hand and timed to the second! Once this step is complete, the water is drained thoroughly to prepare for steaming.

Steaming rice

Soaked rice is steamed to pre-gelatinize its starchy center. The rice is steamed for about 60 minutes. This is done in either a traditional steamer called a “koshiki” or in a continuous rice steamer. Done properly, the outside remains firm and not sticky. Steaming makes rice koji-friendly and soluble. 

After steaming, the rice is cooled. To what extent depends on what the rice will be used for. Rice for koji making is cooled to just under 100 degrees Fahrenheit. The rice for “shubo” (yeast starter) and “moromi” (main fermentation mash) is cooled more.

 Koji making

Samples of Yamadanishiki

Koji rice is evenly spread out to break clumps and reduce heat.

Koji is a fungus that converts the starch in rice into fermentable sugars. Making koji is arguably the most challenging and important step in sake brewing. The process happens in a “kojimuro,” which is a wooden room that’s kept at around 95 F.

Some of the steamed rice is taken into the kojimuro, where work starts on a large table called a “toko.” A cloth is laid over the table and steamed rice is spread out on top. Next, koji spores are sprinkled on top of the rice. The rice is then flipped and more koji spores are added. Everything is then mixed and wrapped in the cloth to keep it humid for the koji.

The rice koji is left to grow for eight or more hours. At this point, it’s clumping and needs to be broken up. The next step is to separate the rice koji into small or medium-sized boxes. This gives the koji oxygen and helps it build up heat. 

Once the koji mold covers about 70% of the rice’s surface, it’s producing too much heat and must be cooled. It’s spread out on the toko and clumps are broken up to release moisture. Rice koji for quality sake is typically allowed to dry for a day before the next step. 

Starter mash (shubo) making

Shubo (or moto) is the sake yeast starter. It’s made of rice koji, steamed rice, water and yeast. Additionally, lactic acid is necessary to resist spoilage. We’ve already touched on the different ways to introduce lactic acid: Sokujo-moto, the method by which pure lactic acid is added directly, is the most common and accounts for about 90% of all sake. It takes about two weeks to finish and produces clean-flavored sake.

Kimoto and yamahai are two related shubo styles. They differ from sokujo-moto in one major way: Instead of adding pure lactic acid, lactic acid is cultivated naturally with the help of ambient lactic acid bacteria.

Kimoto is old-school and uses the physical “yamaoroshi” process to mix the mash to speed up saccharification. It takes about four weeks to complete. Because of the time and effort involved, kimoto accounts for around 1% of sake production.

Yamahai circumvents the yamaoroshi process. By first combining only koji rice, water and careful temperature control, yamahai makes a similar shubo to kimoto. Yamahai accounts for about 9% of sake. 

Both kimoto and yamahai sake are known for their rich and acidic taste. 

Sake moromi making

Samples of Yamadanishiki

These huge tanks at Choryo Brewing Company contain fermenting sake mash.  Photo by Rina Liggett.

Moromi is the main sake mash and fermentation. The initial mashing involves a three-step brewing method called “sandanjikomi” that takes four days. During this time, the size of the moromi increases substantially.

The shubo is combined with rice koji, steamed rice and water on the first day, which is called “hatsuzoe.” The second day is called “odori” (rest period) where nothing is added, but yeast grows in number. More koji, steamed rice and water are added on the third and fourth days, “nakazoe” and “tomezoe,” respectively.

After this process, the moromi is at full size and it’s on to the next step.

Fermentation

At this point, there is a dense cap of risotto-like rice on top of the moromi. Shortly after tomezoe, cracks in this cap and bubbles start to appear.

Starting with tomezoe, the sake fermentation process for futsushu and honjozo takes about 20 days. For ginjoshu, it can take four to five weeks. During this time, brewers must carefully watch the fermentation. The size and shape of the foamy cap provide clues as to how the fermentation is progressing. 

Sake fermentation is unique because the conversion of starch to sugar and sugar to alcohol happens simultaneously. Eventually, the koji exhausts the supply of starch, and the yeast ferments most of the glucose (sugar). Most sake yeast slows down once the alcohol content reaches 16%-18% and above. The “toji” (brewmaster) will make the critical decision around this time when to stop the fermentation. 

Alcohol addition

Honjozo, tokubetsu honjozo, ginjo and daiginjo sake include a small addition of brewer’s alcohol. The alcohol is distilled and neutral — similar to vodka. The addition happens at the end of moromi, before pressing. 

Brewer’s alcohol is added mostly for stylistic reasons. Alcohol-added sake (“arutenshu”) has an enhanced aroma and a lighter taste. The risk of spoilage is also reduced. But this step is also used to increase yield or consumer cost of lower quality sake. 

Pressing and racking (joso)

Samples of Yamadanishiki

A modern, automated sake press called an “assaku-ki” at Fukumitsuya in Ishikawa prefecture.  Courtesy of Fukumitsuya.

Samples of Yamadanishiki

A traditional wooden sake press called a “fune.” The spout at the bottom is where the freshly pressed sake comes out.  Courtesy of Eigashima Shuzo.

The fermented moromi is full of rice sediment and needs to be pressed (“joso”). Joso removes the rice solids (“kasu”) from the alcoholic liquid.

After pressing, the beverage is officially sake! This transparent brew is where the official term for sake comes from: “seishu” (clear sake). 

There are a few sake pressing methods. The most common is using an automated pressing machine, where accordion-like filters squeeze out sake and leave behind sake kasu. The automatic press is efficient and reliable. 

An old-school pressing method uses a “fune,” which is a boat-like box with a large lid over the top. Cloth bags are filled with moromi and carefully stacked inside. Some sake runs out freely, which is called “arabashiri” (rough run). Later, the lid presses down on the bags, squeezing out more sake, which is called “nakadori.” Arabashiri and nakadori are typically blended together but are sometimes bottled individually. Finally, immense pressure is applied, squeezing out a little more sake called “seme.” Seme has a rougher taste and is kept separate from the other portions. 

“Shizukushibori” (a.k.a. “fukurotsuri”) is another hands-on pressing technique. Bags of moromi hang inside a small tank, and the sake that drips from them is collected. This shizuku sake is high quality, rare and expensive. 

To make cloudy sake (nigori), moromi is coarsely pressed, allowing some rice solids into the sake. Alternatively, nigori can be made by adding fresh kasu to clear, finished sake. 

Oribiki

Even after joso, sake contains fine sediments like yeast, starch, etc. The sediment is called “ori” and leaves the sake cloudy. 

Sake is stored at cold temperatures for a few days or more to allow the sediment to settle. The storage tank has a raised bottom and two spouts. Clear sake is collected from the upper spout, while the cloudy ori is taken from the bottom. The process is very similar to racking in winemaking. 

Filtering

Most sake is filtered after pressing and oribiki. This helps prevent spoilage and tweaks the color and aroma.

A variety of filters exist including paper, fine-mesh, cellulose membrane and carbon. Filtering sake with carbon makes sake clear and colorless. Some flavor is also removed, making clean-tasting sake. Paper filtration is the most common method, and it yields sake with more color and flavor. 

Unfiltered sake also includes many variations. It can mean no activated carbon was used (“muroka”), a total lack of filtration or a very coarse filtration. In general, it has a richer flavor, more body and more color. 

Pasteurizing

Most sake is pasteurized twice. Heating stops the enzymatic activity and prevents spoilage from unwanted bacteria, leading to shelf-stable sake. Pasteurization, or “hi-ire,” usually happens after filtration and again before bottling. 

The most common pasteurization method is to pass sake from one tank to another through a coil. The coil is submerged in boiling water. Sake is heated to between 140 F and 149 F for about 30 minutes. 

But not all sake is pasteurized. Unpasteurized sake is called “namazake” (raw sake). Namazake has more intensity and acidity. It must be stored carefully and kept cold at all times. Breweries often release namazake around the end of the brewing season, so spring and early summer are the best times to find it.  

Sake that’s pasteurized only once at this stage is called “namazume” (bottled raw). It retains some of the vibrancy of namazake but is more shelf-stable.

Storing, adjusting and maturation

Samples of Yamadanishiki

Sake quality is personally evaluated to discern if any adjustments are necessary, as seen here at ​​Yaegaki Brewing Company.  Courtesy of Yaegaki Brewing Company.

After hi-ire, sake is typically aged in tanks for up to six months. The sake is kept cool (59 F-68 F) to maintain freshness. Different tanks of sake are tasted and blended for consistency. Sake for export may forgo aging to ship out a fresher product. 

Finally, “warimizu” (water dilution) is performed for several reasons. It can lower the alcohol content and lead to a lighter, smoother sake. It also reduces the sake’s tax rate. 

As mentioned earlier, sake with minimal or no dilution is called genshu. To qualify, the alcohol content cannot be lowered by more than 1%. 

Re-filtering and pasteurizing

After storage and dilution, some sake go through an additional filtration — especially namazake. Most are also pasteurized a second time. This often happens on the bottling line. But pasteurization in the bottle is also common at smaller breweries. 

Sake that is pasteurized only once, after filtration, is called “namachozo” (“stored raw”). Like namazume, namachozo is fresher and brighter than twice pasteurized sake, but less so than namazake. 

Bottling

The last step (finally!) in the sake production process is bottling. The freshly bottled sake may still be warm from pasteurization. Some breweries spray the bottles with cool water on the bottling line. Others let the bottles cool off for a day before packing them in cardboard boxes. 

When sake is boxed warm, other steps may be necessary to ensure heat is dissipated. Leaving space between the boxes and using a blower with cool air are a few methods. Bottles are also labeled and date-stamped after bottling. 

Common sake questions

Samples of Yamadanishiki

Various Japanese beers and spirits.

Your crash course is coming to an end! So let’s answer some common sake questions once and for all.

How is sake different from wine and beer?

Sake is often called rice wine, but it isn’t actually wine. Wine is made from grapes (or other fruit) and their sugary juice. Fermenting wine is a much simpler process, and the quality and flavor is largely determined in the vineyard. Sake is a beverage made of rice with a complex brewing process. Choices made in the brewery largely determine the quality. 

Like sake, beer is a brewed, grain-based beverage. Beer relies on malted barley for saccharification, whereas sake uses koji. The brewing processes are also quite different, leading to two completely different beverages. Sake generally has more alcohol, a lighter color, less bitterness and no carbonation. 

How is sake different from soju or shochu?

Shochu is Japan’s national spirit and is essentially distilled sake. Both use koji, but as a spirit, shochu has a higher alcohol content and is shelf-stable. Sake is only fermented, so it’s lighter, softer and perishable. Sake is also made entirely from rice, while shochu allows a variety of grains and starchy ingredients. 

Soju is Korea’s version of shochu. Most soju brands are mass-produced. Sake and soju have little in common other than the use of koji. 

How is sake different from plum wine and flavored sake?

Flavored sake is a broad category of mostly futsushu infused with fruit, sweeteners and/or other additives. Yuzu and plum are the two most common ingredients in flavored sake. Plum wine (“umeshu”) is different because it doesn’t always have a sake base. Instead, umeshu may have a base of shochu or other spirits. 

How is sake different from cooking sake?

Cooking sake, including mirin, has a lower alcohol content than regular sake and is seasoned. Standard cooking sake typically contains salt and sugar. Quality sake will not contain any additional ingredients. Lower quality cooking sake brands sometimes use ingredients like corn syrup, caramel and acidifiers. 

Demystifying sake

Sake brewing is obviously complex. But you don’t need to be a toji to use this knowledge. Many interesting substyles of sake are derived from the choices outlined above. This background information on the sake brewing process can help you navigate Tippsy’s many categories so you can find your new favorite brew. And this guide will always be here for you to reference when you need it!

References

- “A Comprehensive Guide to Japanese Sake.” JSS and National Research Institute of Brewing, 2011.
- Harper, Philip. “The Insider’s Guide to Sake.” Kodansha, 1998.
- “Sake Adviser Certificate Course.” Sake School of America, 2011.
- “Textbook of Sake Brewing.” Brewing Society of Japan, 2016.
- Tsuji, Shizuo. “Japanese Cooking: A Simple Art.” Kodansha International.
- “J.S.A. Sake Diploma (Coursebook): English.” Japan Sommelier Association (2019).

Next lesson

Lesson 3: What Is Rice Polishing Ratio?

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