Let's learn about sake. Are you ready? I am. I'm also interested in drinking some, but that's beside the point. I have a beer in my hand, so I'll have to give myself a raincheck, for at least the next half hour.
I'm going to go through the sake-brewing process, from start to finish, with a case study based on our trip last fall to Kenbishi, Japan's oldest sake brand. Kenbishi, located west of Osaka in Hyogo Prefecture, has been brewing sake since 1505. The name Kenbishi means "sword diamond," and they've used the same iconic sword-diamond logo for hundreds of years. You can actually see it in some old Edo-period woodblock prints, like the famous Utamaro print below, now at the New York Met.. This is sake with history, a classic brand paired with centuries of technical expertise. The product itself is bold and distinctive, and made a real impression on me even before our trip there.
Kenbishi's current owners--the fourth family to own the brewery--are dedicated stewards of a half-millennium tradition. Masataka and Noriko Shirakashi generously spent four hours with us, giving us a private step-by-step, room-by-room tour of the entire sake-making process, followed by a sake tasting. It was an incredible experience, and a surprisingly intimate one. We learned a ton, not only about how sake is made, but also about how well it pairs with Western foods like cured meats and cheeses. Because they let us bring our camera along for the tour, we have a great photo record to accompany the sake story, and hopefully make it easier to follow.
Sake Brewing Basics
Before we enter the kura (sake brewery), let's make sure we understand some basic sake principles. Sake is a drink made by fermenting rice, which has been milled to remove the outer layers. The fermentation process used to make sake is known as "double-parallel" fermentation. This means two types of fermentation are necessary to make sake, and they happen in the same pot at the same time. First, the starches in rice must be converted into simple sugars. This process is carried out by a fungus, known as koji. Second, as with other alcoholic beverages, yeast (also a fungus) is used to convert sugars to ethanol.
The end product results from controlling an astounding number of variables: the variety of rice, the amount of rice milled, the rice cooking process, the rice moisture content, the species of koji and yeast used, the quality of the water, filtration, pasteurization, aging, and much more. The dedication to the craft, the attention to detail at every step in the process, is the hallmark of sake-making. At Kenbishi, the commitment to traditional methods is on full display. Instead of using synthetic, off-the-shelf ropes for its sake barrels, Kenbishi makes its own ropes in-house. It still manufactures its own rice-steaming barrels and wooden warming elements, just as it has for hundreds of years. No corners are cut, the commitment to the craft drives every step of the process.
We visited Kenbishi's primary kura, one of four. Incredibly, Kenbishi saw huge damage in the 1995 Kobe earthquake. At that time, they had eight kuras. Only one survived. A devastating loss, and one that could easily spell the end for a business. But with 500 years of tradition, the strength of its brand, and the quality of its product, Kenbishi pulled itself up and rebuilt. Today it is thriving. Across four brewing sites, Kenbishi has about sixty permanent employees. During the winter months, peak brewing season, that number doubles with the addition of seasonal workers.
Rice Milling
The first step in making sake is milling the rice down to its starchy core. The milling strips the outer layers, which contain proteins, fats, and other impurities that can compromise the taste of the final product. The process is performed using a milling machine like the one shown below. The powdered outer layers are not discarded; they are used in various cooking applications, for livestock feed, etc.
If you've seen the terms ginjo or daiginjo on a menu, they are indicators of the percentage of rice milled. Ginjo means the sake uses rice milled to at least 60% of its original volume; daiginjo to at least 50%. Often sake is referred to as being "premium" the closer it gets to a daiginjo. The important thing to understand, though, is that this doesn't mean a daiginjo sake is better, or that you'll like it more. It just means (a) it costs more to make because less of the rice grain is used, and (b) it's likely to have a cleaner taste with more of the grain's outer impurity-containing layers having been removed. In other words, ginjo and daiginjo refer to manufacturing styles (and, relatedly, Japanese regulatory and labeling distinctions) rather than to the rank of the sake.
Kenbishi only mills its rice to a bit over 70% of its original volume, and the sake has a big, complex taste. They adjust the exact milling rate each year to make the best use of the rice harvested that year.
Rice Steaming
Once the rice is milled to the desired level, it has to be steamed. Remarkable care is taken to control the steaming process, because the ultimate moisture content imparted to the rice is critical for the success of subsequent fermentation processes. Kenbishi, with its focus on traditional methods, steams rice using large cedar barrels, called koshiki. They believe the wooden koshiki is a superior vessel, because it prevents condensation and absorbs excess water. They steam their rice in the very early morning, to take advantage of cold air coming down from the nearby mountains. It helps with temperature control.
Amazingly, Kenbishi's wooden koshiki are all made by an in-house craftsman, using traditional methods. This particular craftsman is the only person alive today with the know-how to make these things. As it turns out, he's quite old, so for the past five years, he has been training others at Kenbishi to carry on this craft tradition after he's gone. Now Kenbishi is in a position to keep its historical brewing methods alive into the future.
Koji
Once the rice is cooked, a portion is used to make koji. This is done in a special room, which feels a lot like a sauna or a steam room. It's essentially a huge cedar box, kept at elevated temperature and humidity. The brewers begin the process by working the koji spores into the rice by hand. This painstaking manual procedure is necessary to achieve uniform coverage across all grains of rice. The rice is then placed into little open cedar boxes, which are moved around the room four times a day for 4-5 days. This constant rotation is necessary to make sure all the grains of rice are exposed to the same environmental conditions, to promote uniform koji growth. When the growing process is complete, the koji rice is set aside for use in the fermentation tank.
Somewhat surprisingly, we were allowed into the koji room during our tour. It was steamy in there, and you get the sense of how demanding it must be for the brewers to spend so much time in this hot space working around the clock to assure optimal distribution and growth of the koji fungus. We were invited to touch and taste the finished koji rice. You can see in the picture how the look of the rice has changed; it appears to be covered in a matte-opaque white material, and has become a bit clumpy. The taste was pleasant, sort of sweet, and the texture a bit chewy.
Yeast Starter
The next step is to make the yeast starter, also known as shubo. This is the first step that makes it clear alcohol is being brewed. The yeast starter is an oatmeal-like concoction of steamed rice, koji rice, and water, in which yeast propagates. This is where parallel fermentation takes place: the koji is breaking down the rice, converting the starch to sugar, while the yeast is simultaneously taking the koji-produced sugar and converting it to alcohol.
At Kenbishi, the preparation of the yeast starter takes about a month. Most other breweries do it in about half the time because, unlike Kenbishi, they physically mash the rice during the fermentation process, exposing the interior of the grain to the koji enzymes. The process involves a traditional method of slow, indirect heating, using wooden jugs periodically filled with boiling water. Once again, Kenbishi is uniquely traditional here, because they employ the only craftsman in Japan who can still make these wooden jugs.
From a scientific perspective, a lot of cool stuff is happening in the yeast starter, which I'll write about in detail later.
Fermentation Mash
When the yeast starter is complete, it is time for bulk fermentation. Now the process moves to significantly larger tanks, into which yeast starter, koji, steamed rice, and water are added in three intervals over a four-day period. The reason for the intervals is that the transfer to a bigger vessel with more surface area puts stress on the yeast, which need time to adjust to changed environmental conditions. The moromi mash is kept in the tank for about three weeks. At this point, it's time for final processing.
Finishing the Sake
With fermentation complete, the mash is filtered to remove residual solid particulates. There are a number of ways to perform the filtration; Kenbishi uses the press filtration machine in the image below. Be aware, though, that not all sake is filtered to clearness. You may have encountered niigori sake, which is cloudy as a result of filtration using a coarser mesh.
Following filtration, the sake is pasteurized. Not only does this heating process kill bacteria, it stops enzymatic activity in the sake, which helps stabilize product quality. Some breweries also filter their products over charcoal, which helps remove organic impurities and clear up the sake's color. Finally, Kenbishi transfers the sake to large tanks, where they age it before bottling. Their popular kuromatsu product is aged for less than a year, but they have another product that's aged for up to fifteen years.
So now we've gone through the entire sake-making process. It's safe to say the main contours of the process at Kenbishi are representative of how sake is made generally. The steps always include rice milling and steaming, the preparation of koji, and then the yeast starter, before moving on to bulk fermentation. The fine details of an individual brewery's processes, combined with variations in rice, water, microbes, etc., together contribute to each sake's unique characteristics. There are obviously more subtleties to Kenbishi's process, which are too detailed to go into here.
Sake Tasting, With a Surprise
After our tour, we sat down with the Shirakashis for a sake tasting. We tried six products, each aged for different periods of time. Only a couple of them (kuromatsu and kuromatsu mizuho) are available in the U.S. Kenbishi's basic product, kuromatsu, is a bold, rich drink, but it was the lightest sake we tried. Most striking was a sake that had been aged for more than five years, taking on a golden hue and delivering a powerful sensory experience. Not quite a brandy or a liqueur, but trending in that direction relative to most sake out there.
The most eye-opening part of our tasting was that Kenbishi paired its sake with Western foods--blue cheese, Camembert, prosciutto--in addition to some Japanese items, like pickled sea urchin and fermented squid (ika no shiokara). All of these cured or fermented high-umami foods paired well with Kenbishi's strong sake, with the richest sake pairing best with the richest foods, the blue cheese and the sea urchin.
The point is that Kenbishi chooses to showcase its products in an international context, drawing on food pairings best suited to the sake, and disregarding the artificial barrier between this Japanese drink and Western cuisine. Kenbishi is being forward thinking here. It realizes, as a matter of business, that the future of sake is a global one. At the same time the Japanese sake industry sees a shrinking market at home, sake is starting to gain a foothold in the uncharted West, with Americans and Europeans starting to drink it more seriously. Perhaps not surprisingly, we just saw Shirakashi-san at the JFC sake expo in the Bay Area last month, and his Facebook feed says he's been in LA and Italy in the weeks since then.
Kenbishi reveres tradition when it comes to making its product, but it's positioning itself at the vanguard of sake's big extraterritorial expansion. For both of these things, we tip our hats and raise our glasses. Kanpai!