Junmai & Honjozo Sake
Pure rice or small alcohol addition. Koji biology, heiko fukuhakko parallel fermentation, water chemistry — the science of Japan's everyday sake designations.
Codex Definition
Junmai (純米) and Honjozo (本醸造) are the two base premium sake designations under NTA regulations. Junmai means "pure rice" — made only from rice, koji, water, and yeast, with no added alcohol. Honjozo permits a small addition of pure alcohol (maximum 10% of rice weight in pure alcohol) to the final sake. Both require seimaibuai (rice polishing ratio) of at most 70% for Honjozo; Junmai has no polishing minimum under current NTA regulations. These designations form the foundation of the premium sake classification pyramid.
How koji transforms rice into fermentable sugar
Koji mould (Aspergillus oryzae) is the foundation of sake fermentation — and the foundation of many other fermented foods and drinks in East Asian cuisine (miso, soy sauce, mirin, amazake, shochu). Koji produces two critical enzymes: alpha-amylase (breaks the long-chain starch polymers into shorter dextrins) and glucoamylase (completes the breakdown of dextrins to individual glucose molecules). In sake production, the koji is grown directly on steamed rice grains — a process that requires precise temperature and humidity control for 40–60 hours. The koji rice (about 20–30% of the total rice used in a batch) is then added progressively to the fermenting mash alongside fresh rice and water.
The resulting parallel fermentation (heiko fukuhakko) — where saccharification and fermentation occur simultaneously in the same vessel — is what allows sake to reach 18–20% ABV. In beer, all the starch is converted to fermentable sugar before yeast is added; if the yeast were presented with all that sugar at once in a sake batch, the osmotic stress would kill the yeast at much lower alcohol concentrations. The gradual glucose release by koji keeps the glucose concentration low enough for yeast to survive and continue fermenting as the alcohol rises — a self-regulating mechanism unique to sake among major fermented beverages.
Junmai vs Honjozo — the alcohol addition question
Junmai (純米 — "pure rice") means no alcohol is added at any stage of production. The sake is made entirely from rice, koji, water, and yeast. Junmai sake tends to be richer, fuller-bodied, and more umami-prominent — with more of the rice's amino acids contributing to the flavour profile.
Honjozo (本醸造) permits a small addition of pure alcohol (brewed alcohol or grain neutral spirit) at the final stage — up to 10% of the total rice weight (by mass of pure alcohol). This small addition does not sweeten or fortify the sake the way sugar or alcohol additions change a Port wine — it primarily acts to extract aromatic compounds from the rice mash that would otherwise remain bound, and to lighten the body and mouthfeel. The result is a sake that is somewhat lighter, more aromatic, and faster to finish than an equivalent Junmai.
Namazake (生酒) — unpasteurised sake. Standard sake is pasteurised twice (once after pressing, once before bottling) to kill bacteria and stop enzymatic activity. Namazake is bottled raw — very fresh, slightly cloudy, with active enzymes that continue to change character. Requires refrigeration; shelf life is shorter. Highly seasonal in Japan (spring release of new-vintage namazake).
Nigori (にごり) — coarsely filtered sake. Standard sake is pressed through cloth filters to remove rice solids, producing a clear liquid. Nigori sake passes through a coarser mesh, leaving rice solids (lees) in suspension — producing a white/cloudy appearance and a richer, creamier texture with more rice sweetness.
Water chemistry in sake — the nada vs fushimi contrast
Water is perhaps the most critical raw material variable in sake production — 80% of sake's volume is water, and the mineral content of the water determines the speed and character of fermentation. Two of Japan's most celebrated sake-producing regions demonstrate the contrast:
Nada (灘) — Hyogo Prefecture, near Kobe. The water used in Nada sake production is miyamizu (宮水), drawn from specific wells in the Nishi-Nomiya area. Miyamizu is hard water — high in potassium, phosphorus, and magnesium, low in iron. These minerals act as yeast nutrients, accelerating fermentation and producing a dryer, more vigorous sake style. Nada is famous for otokozake (男酒, "man's sake") — dry, firm, robust. Kikumasamune, Hakutsuru, Nada no Jizake.
Fushimi (伏見) — Kyoto. Fushimi water is goshuishui — soft water, low in minerals. Soft water produces a slower, gentler fermentation — a sake style called onnazake (女酒, "woman's sake") — softer, more delicate, sweeter. Gekkeikan, Kizakura.
Iron is the mineral most actively controlled by sake brewers — even trace quantities of iron (above ~0.02 mg/L) inhibit yeast activity and produce browning/off-flavours in the finished sake. Water with naturally low iron content (miyamizu, Fushimi water) requires no iron removal treatment. Source: Yoshizawa and Kishi (1985) Brewing Society of Japan annual report.