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Super-flat rice polishing techniques promise a bright future for ginjo sake
Super-flat rice polishing


Why sake brewing requires rice polishing
The rice germ and outer husk contain large amounts of proteins, oils, ash and vitamins. These compounds change the production balance by accelerating the growth of koji mould and yeast. They also degrade the quality of the finished sake by causing tinting and unwanted flavours. The purpose of the rice polishing process is to remove such elements.

But it is not a matter simply of "the more polishing the better". A high degree of polishing results in a delicately-flavoured sake such as daiginjo. A medium degree of polishing will result in a sake such as junmai sake which has a robust richness that makes it perfect for drinking warm. So variations in rice polishing translate into a rich variety of sake types, and polishing is a vital factor in the final flavour.

Distribution of undesirable elements (black part)
Distribution of undesirable elements (black part)

Many undesirable elements are concentrated in the rice germ. They are found in steadily decreasing quantities as you move further below the surface of the rice grain.

Good rice polishing

  • Keeps cracks, chips, flaws and other problems to a minimum
  • Is completed as fast as possible
  • Removes undesirable elements without wasting the vital rice starch
Problems with old rice polishing techniques


The most widespread polishing technique sought to polish rice as quickly as possible by increasing the rotational speed of the rice-polishing machine roller (whetstone). At the same time the density of rice in the polishing chamber was lowered to prevent cracks and splits.
This made the grains far more likely to rotate wildly on their short axis, leading to more polishing action being applied to the ends of the long axis of a grain. This results in spherical grains.


The principles behind conventional rice polishing
The faster the rotation of the rice-polishing machine roller (whetstone), and the lower the density of rice in the polishing chamber, the more likely the grains of rice are to rotate on their shortest axis, resulting in round grains.

Conventional polished rice
Conventional polished rice (spherical polished rice)

As a result, the rice is polished to an extreme degree at the ends of its long axis, while the shorter, stouter axis is barely touched. The outcome is that the old polishing techniques leave behind undesirable elements on the short axis, and waste precious starch on the long axis. (See chart on left)



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