The classification of premium sake is determined by the Japanese Ministry of Finance. It depends on the degree to which the rice is polished. Six levels are being differentiated.
Polishing ratio: No specifications, better bottlings are generally polished to less than 70%
Additions: Brewed purely from rice and water
Polishing ratio: Less than 70%, better bottlings with addition "Tokubetsu" less than 60%
Additions: Up to 10% brewer's alcohol
Polishing ratio: Under 60%
Additions: Brewer's alcohol, on the last day of fermentation
Process: Long-term cold fermentation at 5-14°C
Polishing ratio: Less than 50%, often down to 35%
Additions: Brewer's alcohol
Process: Very cold fermentation, at 5-9°C
Futsushu is a standard quality, to which alcohol, glucose, glutamate and a few other things may be added. It accounts for approximately 80% of the produced sake and is known for causing a hangover.