Why we throw away 50%: The art of rice polishing (Seimai)
Key Takeaways:
- The polishing rate (Seimaibuai) determines the category (Junmai vs. Ginjo).
- Polishing removes fats and proteins that can lead to off-notes.
- Modern techniques such as "Flat Polishing" (Genkei Seimai) are currently revolutionizing quality.
Imagine buying 100 kg of the finest rice. Then you put it into a machine that grinds it down until only 50 kg remain. The other 50 kg is dust. Crazy? No, that's the prerequisite for Junmai Daiginjo .
Polishing (seimai) is the first and most brutal step in sake production. But why is it done?
The Anatomy of Taste
A grain of rice is structured like an egg:
- Outer layer (shell & rim): This is where proteins, fats, vitamins, and minerals are located. What's good for food is bad for sake. These substances cause "tzatsumi" (impure taste) and make the sake age quickly and turn brown.
- Inside (core/Shimpaku): This is where pure starch resides. Starch is converted to sugar, sugar is converted to alcohol. Pure starch results in pure, fruity flavor.
The more we polish away from the outside, the "cleaner", finer and fruitier the sake becomes.
Understanding Numbers (Seimaibuai)
Every premium sake label has a number on it, e.g. 60%. That's the amount of rice that was left over .
- 70% (Junmai / Honjozo): 30% was ground away. The sake still tastes "rice-like", strong, and has umami.
- 60% (Ginjo): 40% was ground away. The sake becomes lighter, more aromatic.
- 50% or less (Daiginjo): Half the rice is gone! The sake is extremely fine, elegant and often expensive (since twice as much raw material is needed).
High-Tech: Flat Polishing (Genkei Seimai)
In the past, rice was simply milled into a round shape. The problem: the rice grain isn't round, but oblong. Milling it into a round shape removed too much starch from the sides, while protein residue remained at the ends.
The most modern technique is flat polishing (Genkei Seimai) . Computer-controlled rollers grind down the grain in such a way that it retains its original shape, only smaller. This allows for extremely efficient protein removal without wasting valuable starch.
A sake with 60% flat polishing can taste as clean as a sake with 40% round polishing.
Pay attention to the percentage rating next time you buy sake. It doesn't tell you how good the sake is, but it does tell you what style to expect: strong (high number) or elegant (low number).
