How Sake Is Made: Complete Guide

Sake brewing has developed into a sophisticated craft over the centuries. Although there is a standard approach to making sake, the specific choices in each step can significantly influence its flavor.

The process skillfully blends simplicity with detailed craftsmanship, utilizing essential ingredients such as rice, water, koji mold, yeast, and sometimes distilled alcohol in non-Junmai varieties.

This article will detail the steps involved in sake brewing and explain the importance of each one.

The 4 Main Ingredients

Rice serves as the foundational ingredient, selected specifically for brewing. It's polished to remove the bran, exposing the starchy core essential for fermentation.

Water is equally pivotal, as its quality and mineral content significantly influence the sake's flavor, aroma, and texture.

Koji mold is the catalyst in the process, converting the starches from the rice into fermentable sugars. This transformation is critical, as it sets the stage for fermentation.

Yeast then takes center stage, converting these sugars into alcohol, with different strains imparting distinct aromatic profiles to the sake.

The meticulous control of each step—from rice polishing to the fermentation environment—allows brewers to craft sake with varied and complex flavors, ensuring each batch is a refined expression of both tradition and the brewer's artistry.

Polishing

Before brewing can begin, preparation of the rice is crucial. Polishing the rice is a critical first step; this is done because the starchy core, essential for sake production, is at the center of the grain.

The outer layers contain proteins and fats that can impact the taste and aroma of the final product. Balancing the cost of the rice and the desired quality of the sake is a key consideration for brewers.

The polishing rate, or Seimeibuai, indicated on sake bottles, reflects the percentage of the grain that remains after polishing.

For example, a Seimeibuai of 60% means 40% of the outer layer has been removed.

This rate helps classify sake into different categories: Daiginjo requires a polishing rate of 50% or less, Ginjo up to 60%, Honjoshu up to 70%, and any rate higher than that categorizes the sake as Futsushu, or standard sake.

While lower Seimeibuai often signifies higher purity and smoother drinking experience, it's not always indicative of better quality as over-polishing can reduce the sake's complexity and depth of flavor.

Balancing purity with character is essential in crafting high-quality sake.

Washing and Soaking

Once the rice is milled, the next crucial step in sake making is washing and soaking the rice.

Washing the rice serves to remove any bran and residual particles from the milling process. This ensures that the rice is clean and ready for further processing.

Soaking the rice is equally vital as it allows the grains to absorb the right amount of water.

This step must be meticulously managed; over-soaking can result in overly soft rice that doesn't steam well, whereas under-soaking can lead to excessively hard grains, both of which impede the growth of koji.

In the production of higher grades of sake, such as junmai ginjo and daiginjo, the soaking process is often performed manually and timed precisely down to the second.

After soaking, the rice is thoroughly drained, setting the stage for the crucial steaming process.

Rice Steaming

After soaking, the rice is steamed to pre-gelatinize its starch, making it more conducive to fermentation.

The steaming process typically lasts about 60 minutes, utilizing either a traditional "koshiki" steamer or a modern continuous rice steamer.

Proper steaming is crucial; it ensures the rice's exterior remains firm and non-sticky, ideal for promoting koji growth and solubility.

Once steamed, the rice must be cooled. The target temperature depends on its intended use.

Rice destined for koji production is cooled to just below 100 degrees Fahrenheit, whereas rice used for the yeast starter ("shubo") and the main fermentation mash ("moromi") is cooled further to enhance subsequent fermentation steps.

Koji Production

Koji production is a critical and complex step in sake brewing, carried out in a controlled environment known as a "kojimuro," a wooden room maintained at about 95 degrees Fahrenheit.

Here, some of the steamed rice is spread over a cloth on a large table called a "toko." Koji spores are then evenly sprinkled onto the rice, which is subsequently mixed and wrapped in the cloth to maintain humidity, aiding the growth of the koji.

After about eight hours, the rice begins to clump together due to the growth of the koji, necessitating that it be broken up. The rice is then transferred into smaller boxes, which helps provide the necessary oxygen and facilitates heat buildup.

As the koji mold covers approximately 70% of the rice's surface and generates excess heat, it needs to be cooled.

This is done by spreading it out on the toko and breaking up clumps to release moisture. For high-quality sake, the koji rice is usually allowed to dry for a day before proceeding to the next stage of production.

Creating the Yeast Starter (Shubo) for Sake

Shubo, also known as moto, is the yeast starter crucial for sake brewing. It comprises rice koji, steamed rice, water, yeast, and lactic acid, which is essential for preventing spoilage. There are several methods for introducing lactic acid into the shubo:

1. Sokujo-moto: This is the most prevalent method, used in about 90% of sake production. It involves directly adding pure lactic acid to the mixture. This process, which takes about two weeks to complete, results in sake with a clean flavor.
2. Kimoto and Yamahai: These traditional methods differ from sokujo-moto by naturally cultivating lactic acid using ambient bacteria, rather than adding it.
   • Kimoto is the more labor-intensive method, incorporating a physical process called "yamaoroshi" to accelerate saccharification, taking about four weeks. This method accounts for roughly 1% of sake production.
   • Yamahai eliminates the yamaoroshi step, relying instead on careful temperature control and the initial combination of koji rice and water. This process, making up about 9% of production, yields a shubo similar to kimoto.

Both kimoto and yamahai are celebrated for producing sake with a rich, acidic flavor, distinguishing them from the cleaner taste of sokujo-moto sake.

Making Sake Moromi: The Main Fermentation Mash

Moromi, the primary fermentation mash in sake production, undergoes a detailed three-step brewing process known as "sandan jikomi" over four days, during which the mash volume significantly expands.

The process starts with "hatsuzoe," the initial mixing on day one, where shubo (yeast starter) is combined with rice koji, steamed rice, and water.

The second day, termed "odori," serves as a rest day, allowing the yeast population to increase without further additions.

The brewing continues on the third and fourth days, known as "nakazoe" and "tomezoe," during which additional koji, rice, and water are incorporated.

After completing these stages, the moromi reaches its full volume and is ready for the next phase in the sake production process.

Sake Fermentation Process

During the fermentation of sake, a thick, risotto-like cap of rice forms on top of the moromi. This cap begins to show cracks and bubbles soon after the final addition phase, known as "tomezoe."

The duration of fermentation varies by type of sake: it lasts about 20 days for futsushu and honjozo, while ginjoshu may require four to five weeks.

Throughout this period, brewers must vigilantly monitor the process. Observations of the size and shape of the foamy cap are crucial as they indicate the progress of fermentation.

Sake's fermentation is distinctive because it involves simultaneous starch-to-sugar and sugar-to-alcohol conversions.

This continues until the koji depletes the available starch and the yeast converts most of the glucose into alcohol.

Typically, sake yeast activity diminishes when the alcohol concentration reaches 16%-18%. At this critical juncture, the toji (brewmaster) decides when to halt the fermentation, based on the desired sake profile.

Adding Alcohol to Sake

In the production of certain sake types, such as honjozo, tokubetsu honjozo, ginjo, and daiginjo, a small amount of distilled, neutral brewer’s alcohol—similar in nature to vodka—is added. This addition is made at the end of the moromi stage, just before the pressing process.

The incorporation of brewer’s alcohol primarily serves stylistic purposes. It enhances the aroma and imparts a lighter taste to the sake, known as "arutenshu." Additionally, this step helps reduce the risk of spoilage. While it can also be used to increase the yield or affect the consumer cost, particularly in lower-quality sake, its primary role is to refine and define the sake's character.

Sake Pressing and Clarification (Joso)

Once the fermentation of moromi is complete, the next step is pressing, known as "joso," which separates the rice solids, or "kasu," from the alcoholic liquid.

This process yields the clear beverage officially termed "seishu" (clear sake).

Several methods are employed for pressing sake:

1. Automated Pressing: The most prevalent method involves an automated machine that uses accordion-like filters to efficiently extract sake from the kasu. This method is favored for its efficiency and reliability.
2. Traditional Fune Pressing: An older technique uses a "fune," a boat-like box where cloth bags filled with moromi are stacked. Initially, some sake, called "arabashiri" (rough run), flows freely. Additional pressure then extracts "nakadori," a higher-quality sake. The two are often blended, although they can also be bottled separately. Finally, immense pressure yields "seme," which has a rougher taste and is usually kept separate.
3. Shizukushibori (Drip Pressing): In this labor-intensive method, bags of moromi are suspended over a tank to collect the dripping sake, known as shizuku sake. This method produces high-quality, rare, and expensive sake.

To create cloudy sake (nigori), moromi is either coarsely pressed, allowing some rice solids to remain, or fresh kasu is added to clear, finished sake, providing a different texture and flavor profile.

Oribiki: Clarifying Sake Post-Pressing

After the pressing process (joso), sake often retains fine sediments such as yeast and starch, known as "ori," which can leave the beverage cloudy.

To clarify the sake, it is stored at cold temperatures, allowing these sediments to settle. The storage tanks are specially designed with a raised bottom and two spouts to facilitate this process.

Clear sake is drawn from the upper spout, separating it from the cloudy ori collected from the lower spout.

This clarification step is similar to the racking process used in winemaking, where the clearer liquid is separated from its sediments.

Sake Filtration Methods

After pressing and oribiki, most sake undergoes filtration to enhance stability, color, and aroma. Various filtration methods are employed, each affecting the sake's final characteristics:

1. Carbon Filtration: This method uses activated carbon to produce a clear, colorless sake. While it results in a cleaner taste, some flavors may be diminished.
2. Paper Filtration: The most commonly used method, paper filtration allows more color and flavor to remain in the sake, providing a richer profile.

Unfiltered sake, referred to as "muroka," involves no use of activated carbon and may include no filtration or very coarse filtration.

Generally, unfiltered sake boasts a richer flavor, fuller body, and deeper color, offering a distinct experience from its filtered counterparts.

Sake Pasteurization Process

Most sake undergoes pasteurization twice to enhance its stability and shelf life.

This process, known as "hi-ire," typically occurs once after filtration and again before bottling. During pasteurization, sake is heated to between 140°F and 149°F for approximately 30 minutes.

The most common method involves transferring sake through a coil submerged in boiling water, effectively stopping enzymatic activity and preventing spoilage by unwanted bacteria.

However, not all sake is pasteurized. Namazake, or unpasteurized sake, is known for its intense flavor and higher acidity.

Due to its sensitivity, it requires careful storage and constant refrigeration.

Namazake is often released towards the end of the brewing season, making spring and early summer ideal times to find it.

Namazume is sake pasteurized only once, typically when it's bottled. This partial pasteurization allows it to retain some of the freshness and vibrancy of namazake, yet it remains more shelf-stable than its fully unpasteurized counterpart.

Sake Storage, Adjustment, and Maturation

After the pasteurization process ("hi-ire"), sake typically undergoes a maturation period in tanks for up to six months, maintained at cool temperatures between 59°F and 68°F to preserve its freshness.

During this phase, different batches of sake are sampled and blended to ensure consistency in flavor and quality. Sake intended for export may skip this aging process to maintain a fresher profile upon arrival.

The final adjustment often involves "warimizu" (water dilution), which serves multiple purposes.

It not only lowers the alcohol content, making the sake lighter and smoother, but also reduces the tax rate applicable to the product.

Sake that undergoes minimal or no dilution is known as "genshu." To fall under this category, its alcohol content must not be reduced by more than 1%, preserving its robust character.