Rice kernel make up

Last week we looked at a sketchy version of the history of rice leading to the rice we use for making sake at home. This week, we’ll look into the rice kernel itself. Brewing refined sake requires that we remove many layers of the rice, but why? Well before we get to that, let’s look at what these layers are.

Illustration by Namazu-tron ¹

(1): Chaff (2): Bran (3): Bran residue (4): Cereal germ (5): Endosperm

A: Rice with chaff

B: Brown rice

C: Rice with germ

D: White rice with bran residue

E: Musenmai, “Polished rice”

F: Shinpaku, a high starch content in the core

The outer most layer of freshly harvested rice is the chaff. This is a layer that protects the inner seed of the grain. Below is a picture of rice chaff that has been removed from the grain.

Once the chaff has been removed we are left with brown rice. Brown rice appears brown because of the bran outer layer. This bran outer layer contains vitamins, dietary minerals, oils, fatty acids, dietary fibers, starch and protein. The vitamins include B1, B3, B12 and a form of E. Minerals include magnesium and iron.

Brown rice is about 70-75% starch. Starch is by far the most abundant component of rice. Next come protein at about 7-8%. Protein is more prevalent in the outer layers of the grain. Fats make up about 2%. Both saturated and unsaturated fatty acids are present with the center having more saturated fatty acids while the outer layers have more unsaturated fatty acids. Ash makes up about 1% of the grain and includes: potassium, phosphorus, magnesium, and calcium.

While brown rice is much more nutritious than the standard white rice it also goes rancid much more quickly because of its oils and fatty acids that are mostly in the bran.

The bran, bran residual and germ are removed through a milling process to produce white rice. This is your standard table rice processing which leaves only the endosperm, the inner 93-90% of the rice kernel.

Special sake rice (sakemai) has an area in the center of the endosperm that is called shinpaku. Shinpaku is the starchy ball at the center and is really just more prevalent in sake rice than in table rice. The more prevalent the shinpaku the more suited the rice is for sake making. This is, in part, due to its synergy with the milling process.

Rice milling for sake goes beyond the milling of table rice. The goal is to remove more of the fatty acids and proteins leaving only the starchy center. In the extreme only little more than the shinpaku is left.  The more of the outer layer that is removed the more refined the sake. Milling grading uses the seimai-buai scale. This is the percentage of rice left after milling. Using this scale, sake is graded as follows:

–         90% to 71% seimai-buai is Futsu-shu

–         70% to 61% seimai-buai is Junmai-shu or Honjozo-shu²

–         60% to 51% seimai-buai is Junmai Ginjo-shu or Ginjo-shu

–         50% and below seimai-buai is Junmai Daiginjo-shu or Daiginjo-shu

The difference between the Junmai and the other alternative (i.e., Honjozo) is that the later has some brewers alcohol added while the former does not.

So, why do sake brewers want to remove the outer layers of rice? Well, bran and its oils (10-15% of the bran), the fatty acids (the unsaturated ones) and proteins do not interact well with the yeast to produce desirable flavors and aromas. So, by removing the outer layers that contain the highest concentration of these unwanted components, we can brew better, more refined, sake.