Japanese Kome No Hana Rice Culture Polishing Ratios Seimaibuai and Rice Quality Grades
Japan (national; rice cultivation established from 3rd century BCE Yayoi period)
Rice polishing ratio (seimaibuai — 精米歩合) is the most important technical concept in Japanese premium rice culture, applying directly to both sake brewing and the increasingly sophisticated world of artisan table rice. Seimaibuai expresses the percentage of rice remaining after polishing: 100% = unpolished (genmai/brown rice); 70% = 30% of outer grain removed (standard table rice); 60% = ginjo sake threshold; 50% = daiginjo sake threshold; 23% = the current polishing extreme (used for ultra-premium sake). For table rice, recent artisan trends have returned to higher-seimaibuai (less polished) rice for greater flavour complexity and nutrition: haigamai (胚芽米) retains the germ but removes bran; zakkokumai (雑穀米) blends multiple grain types. Koshihikari (コシヒカリ) remains Japan's dominant table rice variety (approximately 35% of total production), prized for its stickiness, sweetness, and aroma. Premium regional varieties include Tsuyahime (Yamagata), Nanatsuboshi (Hokkaido), Hinohikari (Kyushu), and Milky Queen (Ibaraki). The annual rice quality competition (Nihon Ichi Umai Kome Concours) ranks varieties and growing regions annually.