Grape juice arrives with everything already in it — sugar, water, acid. Rice arrives with none of them.
The water a brewer adds. The sugar and the acid have to be made, and they are made by living things: a mould, then a yeast, and sometimes a bacterium as well.
Some tōji I have met describe the work as something close to raising a child. You cannot make a microorganism do anything. You can set the temperature it wakes up in, decide how much food it will find, and choose the moment to stop. Everything after that is the organism's own doing.
A brewer makes hundreds of these decisions between the field and the bottle. Here are four of the largest.
Throwing away most of the grain
Rice arrives at the brewery brown, and the first thing that happens to it is removal. This cannot be done by hand, and it is slower than it sounds: taking off thirty per cent of the grain takes about ten hours, and taking off half can take forty-five.
The figure printed on the label is the polishing ratio, and it counts what remains rather than what has gone. Seventy per cent means thirty per cent was removed. Sixty per cent or less is what the ginjō categories legally require. The most extreme examples go to thirty-five and below, by which point almost nothing is left but the starchy centre of the grain. One brewery has gone to 0.85 per cent, which took two hundred and twenty-one days of polishing and threw away 99.15 per cent of every grain.
The outer layers carry protein and fat. Protein is where umami comes from, but the same layers also bring a coarser texture and aromas a brewer may not want. Polish lightly and you keep that savoury weight, along with cereal and lactic aromas. Polish hard and you have removed the raw material for it — which is precisely the point, if the sake you are after is a pure and fragrant one.
So this is not a technical setting. It is a choice about what kind of sake this is going to be, made before anything has been brewed at all.
The one ingredient that has to be alive
Rice, water and yeast can all be ordered and delivered. Kōji cannot. Kōji is two things put together: steamed rice, and a kōji mould grown onto it. It has to be grown from scratch every single time, and it takes two days.
The mould is native to Japan. What it makes is enzymes, and those enzymes cut starch into sugar and protein into umami. So the brewer is not only feeding the yeast here. How savoury the sake turns out owes a great deal to this room.
And it comes down to how much mould they let grow. More spores, more mould, more enzymes. The mould has to take hold across every grain, on the surface and reaching inside, and directing it to do one and not the other is where the skill sits. Machines exist and work well, but hands are believed to be more precise, and so it is done by hand in most breweries. Which means somebody sleeps at the brewery.
None of it works unless the rice arrives in the right condition. Grains that are too wet grow too much mould, so the water they take on is managed long before this, back at the washing and soaking. Rice polished past halfway can absorb too much in twenty minutes, and that is soaked in small batches by hand, timed on a stopwatch. Rice polished less can be left for hours without much risk.
A yeast that should not survive
Sake yeast lives a life that would kill the yeast in your wine. It keeps working at eight degrees, and it keeps working past twenty per cent alcohol. Wine yeast manages neither. It survives because the sugar never arrives all at once.
Grape must has all its sugar on day one. Here the enzymes release sugar and the yeast eats it at roughly the same rate, both running in the same tank at the same time. A slow trickle is what keeps the yeast going long after wine yeast would have stopped.
Before any of that, the brewer has to raise the yeast itself. A small batch is built whose only job is to grow a healthy population, and lactic acid keeps everything else out while it grows. The brewer can add that acid straight in, which takes about a fortnight. Or they can wait for lactic acid bacteria to arrive and make it, which takes a month and is a nervous month. Sake made the slow way tends to carry higher acidity, and sometimes a note of mushroom or cheese.
Then temperature. Cold and slow gives the fragrant, delicate styles; warmer and quicker gives everything else. The difference is only a few degrees, and it is the difference between two sakes you would never mistake for each other.
Knowing when to stop
Nothing tells the brewer that fermentation is finished. They decide, and then chill the tank until the yeast gives up, at somewhere between seventeen and twenty per cent, with a little sugar still unfermented.
Pressing comes next, separating the sake from the lees — and it is the one step Japanese law requires, which is why textbooks call it filtration. Most sake is squeezed out under pressure. A brewery's finest bottles are hung in cloth bags instead and allowed to drip, with nothing but gravity to move them. Leave some of the rice particles in rather than taking them all out, and you have nigori, cloudy and white.
Then the sake is heated to around sixty degrees to destroy the enzymes, and left alone for six months to a year while the aromas settle. Skip that heating and you have nama: less stable, and more vivid for it.
Water brings the alcohol down to the fifteen or sixteen per cent you actually pour. Skip that too, and it is sold undiluted.
📍 In your glass
Last time you bought a junmai. Buy a junmai ginjō now and put them next to each other, for instance, Sakaya Hachibei, Kid, Miyakanbai, or whichever you can find.
Melon wrapped in prosciutto on the table. The ripe fruit meets the ginjō aromas head on, and the salt does what salt always does to sake.
Taste the junmai first, then the ginjō. More of the grain was thrown away for the second one, and less mould was grown on what remained. You should find the savoury weight has thinned and something more fragrant has come forward in its place. Then eat, and taste both again. Notice which one the ham changes more.
That difference was set in motion long before either bottle reached you — at the polishing machine, in a room somebody was sleeping next to, at a tank someone decided to chill.
The next step
Everything here is easier to hold onto once you have tasted it side by side. That is really all a course is for.
WSET Sake Course
Level 1 Award in Sake is a single day in Amsterdam: six hours, a guided tasting through the main styles, and an internationally recognised certificate at the end.
Level 2 goes considerably further into how each of these decisions shapes what ends up in the glass.
More in this series
Reading a Sake Label
Most of a label is not for you. Five words predict how a bottle will taste — and one character, a jar drawn three thousand years ago, unlocks the rest.
How Sake Is Made
Rice has no sugar and no acid. Both are made by living things — and four decisions a brewer makes along the way separate one bottle from the next.
What Is Sake?
Four ingredients, and no sugar in any of them. Where sake comes from, what a brewer can do with it, and how to stop guessing at the shelf.
