Koji, rice and everything rise: Secrets of sake brewing
In Japan, winter’s a great time to keep warm with some sake (酒). But there’s another lesser-known appeal: it’s when you get to savour sake fresh out of the brewery! That’s right, sake is only produced in winter.
View of Mount Hakusan just down the road from Kaetsu Brewery, source of the fresh waters that make Ishikawa’s sake so good. (Image credit: Komatsu City)
And so, I took the chance this winter to appreciate my drink of choice on a deeper level: through a tour of the 150-year-old Kaetsu Brewery (加越) in Komatsu City (小松市 Komatsu-shi), Ishikawa Prefecture (石川県 Ishikawa-ken). It turned out to be not just a lesson on the production process, but also the rich culture and language intertwined with sake’s long-running history.
Into the sake brewery
Still some specks of green in Kaetsu’s sugidama. (Image credit: Hui Min)
The first thing you may notice at a sake brewery (酒蔵 sakagura) in winter is a peculiar bristly ball hanging at the entrance. Made of cedar branches, these sugidama (杉玉) signal to customers when the season’s fresh batch of sake is out. Starting out green, they dry to brown as the sake matures.
Stepping in, we are greeted by our guide for the day: Mr. Yamada, the owner of the brewery himself. He starts with an introduction to the base ingredient of sake: rice. But not the rice we’re used to eating!
Sake rice (left) versus usual eaten rice (right). (Image credit: Hui Min)
Turns out sake rice is not particularly yummy, lacking the fluff that Japanese rice is known for. But it serves its function well; the first essential step involves polishing the rice much like how brown rice is polished white, which sake rice is especially suited for. In fact, this step determines the sake’s grade category. While only 10% is removed for the rice we eat, for the most premium daiginjo (大吟醸) sake, no more than 50% of the grains must be left. When picking your sake, just remember that the lower the polishing ratio (精米歩合 seimai buai), the higher the sake grade.
The most important step: Kōji (麹) mould cultivation
Perhaps the most sacred room in any sake brewery: the kōji cultivation room. (Image credit: Hui Min)
We quickly delve into the heart of sake-making in the first room, where the kōji mould is cultivated through addition of kōji starter to steamed rice. Mr. Yamada stresses that this is the most vital process. Sake production involves two steps: the conversion of rice starch to sugar, then sugar to alcohol, and the amylase contained in kōji is responsible for the former. Amylase is the same enzyme found in our saliva, and those who have watched the animated movie “Your Name” (君の名は Kimi no Na wa) may recall a scene where rice was chewed and then left to ferment into sake. Indeed, this was one old way of making sake, and some believe that the term for brewing, kamosu (醸す), derives from the term for chewing, kamu (噛む)!
Kōji. (Image credit: Hui Min)
You’d think that mould shouldn’t be hard to grow, given that it often appears where it’s unwanted. But with these precious kōji, care is taken to maintain the environment just the way they like it, at a warm 30℃ and 60% humidity. “We welcome the warmth too”, jokes Mr. Yamada as he adds that workers often find it hard to leave this sanctuary.
Only the kōji for premium daiginjo get to enjoy this “premium treatment” in a traditional wooden sauna. (Image credit: Hui Min)
The second-most important step: Shubo (酒母) cultivation
Fermenting shubo. (Image credit: Hui Min)
The next process we’re shown is of course the second-most vital step: cultivation of shubo, which contains the yeast converting sugar into alcohol. Yeast is first fermented with water and kōji, before steamed rice is added to promote growth. While kōji cultivation takes two days, shubo requires two weeks. Also unlike kōji, yeast likes it cold, but is more unpredictable, requiring Mr. Yamada to adjust temperatures daily, based on intuition and experience.
All set for brewing
The mixture at Day 1 (left) becomes the porridge-like moromi after several weeks (right). (Image credit: Hui Min)
With all the essential components ready, it’s time to make the sake itself. The shubo is added to a large tank, followed by a mix of steamed rice, kōji and water. But as with all good things, patience is required! This mixture is added stepwise in three portions, and the entire process takes up to a month, as it transforms into a state known as moromi that resembles porridge—an audibly bubbling one at that!
Here, Mr. Yamada enlightens us on the difference between beer and sake. First, the science: while both involve conversion of starch to sugar, then sugar to alcohol, for beer these are split into two distinct procedures, while for sake they happen simultaneously with everything mixed in the same tank. But there’s a cultural aspect too: Japan has a strong tradition of using mould for fermentation, extending beyond sake to soy sauce and miso.
This is due to the relative humidity favoured by mould. In places like Europe, the dryness makes mould cultivation impractical, which is why products like beer are fermented with malt instead.
Final touches
(Anti-clockwise from top-left) Modern sake pressing has been sped up with machines, but for the good stuff, Kaetsu uses the traditional funaba for a slow but gentle press. For the very best, bags of sake are hung to filtrate purely by gravity. (Image credit: Hui Min)
Finally, we come to the last step—pressing the completed brew. This is done so as to remove the active mould and yeast that will carry on fermenting otherwise, which some probably prefer not to consume (more on that later). However, in true Japanese fashion of minimising waste, the sake kasu (酒粕) filtered out are not disposed. Sake kasu is thought to be highly nutritious and used for amazake as well as a marinate for many dishes.
At last, tasting time!
From left to right: the unpasteurised nigorizake, three years aged koshu, and unfiltered muroka. (Image credit: Hui Min)
My head spins with more questions and confusion from the complexity of it all, but I’m put at ease as we arrive at the most awaited segment: tasting! Kaetsu has prepared three very different samplings. Just when I thought lesson time was over, we now hear about the diverse ways of refining sake. As just a small sample of that diversity, the first we’re given to try is a kassei namazake (活性生酒), an unpasteurised variation of coarsely-filtered cloudy sake (にごり酒 nigorizake). Next is the unfiltered muroka (無濾過). Both contain living yeast and enzymes, which is why they are only sold in winter and must be kept cold. Finally, we have one that has been aged three years, emitting an amber hue typical of aged koshu (古酒).
So which was the best? As the great variety suggests, to each their own. Nigorizake and muroka versions add complex flavours, but those who prefer a clean simple taste would want their sake well-filtered. As for me, I bought all three without hesitation—enough to last me this winter!
I know it was confusing, so hopefully my diagram helps! (Image credit: Hui Min)
Header image credit: Hui Min
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