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Rice "polishing" through biology?

Hello All-

I’m a total sake newbie, but has there ever been attention given to non-mechanical ways of milling down rice, such as through some sort of chemical/biological reaction?

My understanding is that people mill down rice toward the core where undesirable fats and proteins are less concentrated. The more you mill, the fewer the undesirables, and the more pure the final Sake.

This is not an uncommon problem, anthropologically speaking. Mezo-Americans used nixtamalization (soaking maize in an alkalai solution) to weaken the hulls of corn, unlock “desirable” nutrients, etc. And our bodies use many enzymatic processes to break down or remove undesirable elements of our food so the rest can be digested.

My initial thought was just using the enzymatic processes of Koji. Is there a method where you could give the Koji enough time to break down the outside of the rice, but kill the reaction prior to reaching the core? Then you would discard the byproduct (or feed it to the hog) and then start your actual fermentation. Alternatively there could be a chemical process that removes the proteins and fats you don’t want.

Anyway, this was just pie in the sky thinking, and I was curious to know whether any traditional methods attempted this or not.

Interesting idea. I have not seen any work along these lines. It seems that you would still need some mechanical process to separate what you would discard versus keep.

Part of the breeding of sake rice amounts to attempts to increase the separation of good vs. bad contents. That is to make a higher percentage of the proteins and oils to reside on the outer most layer while increasing the concentration of high quality starch in the center. This allows higher grade sake from lower milling levels.

This seems like it could potentially be done.

I would suggest the following procedure for preparing rice:

  1. wash rice
  2. soak rice in water containing lipases and proteases
  3. wash rice
  4. drain rice (keep water for later use)
  5. steam rice

You could potentially skip step 1.
This should remove unwanted outer layers of the rice and keep the wanted intact.

Well, I’ll start doing some work over the next few months as I brew regularly.

My first thought is to try doing a koji inoculation with undercooked rice, so that it can easily feast on the outside of the rice, then after a certain time, discard the liquid, and start over. We’ll see how it works.

Interesting… Grow Koji around 86-89F to favor protein enzymes.

Interesting lipase info, for lipase production


Growing Koji around 75-78F favors lipase production.

With a short (albeit crappy) research, lipase in general like 30-60C optimal operation temps, so somewhere around 40C.

Essentially, if washed, semi-soaked rice were to be added to a solution of specifically grown koji for this process and the water was heated to 104-110F proteins and fats should be broken down fairly quick. If the proteins and lipids are accessible and not locked up in the starch-matrix which becomes broken down during steaming (starch becomes water soluble), this might work.

Another option is to add steamed rice to this water mixture for 30 minutes, rinse and add to the fermentor… Some soluble starch will be lost, but the broken down lipids and proteins get washed away.

I bet it could work, but industrially - milling and growing the right rice would be much cheaper…

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