Japanese Sake Brewing Calendar: Stages from Shubo to Shiboritate

Japan — sake brewing traditions documented from the Nara period (710–794 CE); the formalised three-stage addition and seasonal brewing calendar established in the Edo period

The Japanese sake brewing calendar follows a highly precise seasonal and technical rhythm that is inseparable from the seasons of rice agriculture — sake is brewed in the cooler months (roughly October through March) when ambient temperatures facilitate controlled fermentation, and the brewing year (BY) begins on July 1 to capture a full brewing season. Understanding the sequential stages of sake production gives beverage professionals the vocabulary to discuss sake with confidence and to understand why seasonal release sake (shiboritate, hiyaoroshi) has value that standard non-vintage sake does not. Stage 1 — Seimei (精米, rice polishing): the harvest brown rice is milled to remove the outer protein- and fat-rich layers, with the polishing ratio (seimaibuai) determining the grade classification. This occurs before the brewing season. Stage 2 — Steaming (蒸し, mushi): milled rice is washed, soaked, and steamed in a wooden koshiki steaming vessel. Some steamed rice goes to koji production; some goes directly to fermentation. Stage 3 — Koji production (製麴, seikyoku): Aspergillus oryzae mould is cultivated on steamed rice over 40–48 hours in a controlled temperature chamber (koji muro), breaking down starches into fermentable sugars. Stage 4 — Shubo (酒母, yeast starter): a small fermentation vessel where yeast is cultivated in a mixture of koji, steamed rice, water, and lactic acid (kimoto, yamahai) or added lactic acid (sokujo). Stage 5 — Moromi (醪, mash): the main fermentation, where the shubo yeast starter, additional koji, steamed rice, and water are added in three stages (sandan-shikomi) over 3 days to prevent temperature shock to the yeast. Moromi ferments for 20–30 days (ginjo grades longer). Stage 6 — Pressing (上槽, joso): the fermented moromi is pressed to separate sake from the rice solids (sakekasu), using a traditional fune (boat press), modern Yabuta machine, or hanging bags (fukuro-shibori for premium gravity-drip sake). Stage 7 — Pasteurisation and maturation before bottling.

Stage-dependent: shiboritate is fresh, slightly effervescent, raw-grain forward; aged sake develops caramel, dried fruit depth; ginjo/daiginjo aromatics (fruity esters) are produced specifically by the low-temperature moromi fermentation