Choose your fermentation vessel
- Rice cooker on 'keep warm': most convenient — check temp (should be 55–65°C), stir every 2h
- Thermos (wide-mouth): most portable and energy-efficient — preheat, fill at 60°C, seal
- Yogurt maker: precise temperature, good for regular batches
- Dehydrator at 60°C: excellent for large quantities, requires a sealed container inside
- Oven light only: typically too low (35–40°C) — not recommended
Ingredients and equipment: what you actually need
The core ingredients are three: dried rice koji (kome koji), cooked short-grain rice, and water. The ratio is 1:1:1 by weight — 200 g koji, 200 g cooked rice, 200 ml water — for a 600 ml batch that serves 3–4 as a drink. Scale linearly for larger batches.
Rice koji (kome koji): dried rice that has been inoculated with Aspergillus oryzae mold — the enzyme source. Available at Japanese grocery stores, health food stores, and online. Dried koji has a shelf life of 6–12 months sealed; once opened, use within 3 months and keep refrigerated. Find rice koji on Amazon →
Equipment needed: cooking thermometer (essential — not optional), clean glass or ceramic container, the fermentation vessel of your choice, immersion blender for smooth amazake.
→ If you want to make your own koji from scratch: How to Make Koji
Temperature control: the one non-negotiable
Rice koji contains two key enzymes for amazake: amylase (converts starch to sugar) and glucoamylase (converts complex sugars to simple glucose). Both are most active between 55°C and 60°C. Above 65°C, they begin to denature and lose activity. Above 70°C, they are essentially destroyed.
Before you start, test your fermentation vessel:
- Fill with water at 60°C
- After 1 hour, check temperature — should be 50–65°C
- After 4 hours, should still be above 50°C
- If temperature drops below 50°C before 8 hours, reheat the mixture to 60°C and return to the vessel
For rice cookers: check your model's keep warm temperature. Many newer models keep at 65–68°C, which is too high — enzymes will be gradually destroyed. If your keep warm setting runs above 65°C, leave the lid slightly open to allow heat to escape.
→ How koji enzymes work: What Is Koji
The fermentation process: what to expect at each stage
0–2 hours: the mixture smells starchy and faintly sweet. Grains remain distinct. No visible activity. This is normal.
2–5 hours: the mixture becomes noticeably more liquid as the enzymes break down starch. A faint sweetness is detectable on tasting. The koji grains begin to soften and the texture becomes more uniform.
5–8 hours: the liquid portion tastes clearly sweet. The koji grains have fully softened into the base. This is the active phase — do not rush it by increasing temperature.
8–10 hours: optimal doneness window. The amazake should taste naturally, cleanly sweet — like a mild rice milk with concentrated sweetness. Taste at 8 hours; if the sweetness is mild, ferment another 1–2 hours.
Beyond 10 hours: lactic acid bacteria present in the koji begin to produce acid, and the amazake gradually turns sour. Over-fermented amazake is not unsafe, but it loses its characteristic clean sweetness.
→ What to do with finished amazake: How to Use Amazake
Finishing, storing, and adjusting the amazake
After fermentation, you have two consistency options: blend for smooth amazake (suitable as a drink — add water to thin to drinking consistency: 1:1 to 1:2 amazake to water); or leave chunky for use as a sweetener or sauce base.
To halt fermentation: heat to 75°C for 1 minute (microwave or stovetop) before refrigerating. This deactivates residual enzyme activity and stabilizes the sweetness level. Refrigerate for up to 5 days; freeze for up to 3 months.
Seasoning: serve plain warm; add grated fresh ginger (1 tsp per 150 ml serving) for a warming drink; add a pinch of salt to enhance sweetness perception for cooking use.
Frequently Asked Questions
Why doesn't my amazake taste sweet after 8 hours?
The most common cause is temperature too low. The amylase enzymes in rice koji are most active at 55–60°C. Below 50°C, the enzymatic conversion is very slow — fermentation will eventually happen but takes 16–24 hours rather than 8–10. Check your temperature with a thermometer at the start and midpoint of fermentation. Most 'keep warm' settings on rice cookers are within range (55–68°C), but they vary by model. A yogurt maker or thermos with hot water gives more consistent temperature control.
What is the difference between this amazake and the alcoholic kind?
There are two types of amazake. Koji-based amazake (kome koji amazake) — made by fermenting rice with koji at 55–60°C — is non-alcoholic. The enzymes break down starch to glucose but no alcohol is produced because yeast fermentation does not occur at 60°C. Sake-lees amazake (sake kasu amazake) — made by diluting the byproduct of sake production with hot water — contains residual alcohol (1–8% ABV depending on dilution). This recipe makes the non-alcoholic, koji-based version. If you are avoiding alcohol, verify your source is kome koji amazake.
Can I make amazake without a rice cooker?
Yes. The best non-rice-cooker method is a wide-mouth thermos: preheat the thermos with boiling water for 5 minutes, discard, add the rice-koji mixture at 60°C, seal, and it will maintain temperature in the 55–65°C range for 8–10 hours. Check the temperature when you open it — if it dropped below 50°C (feels only warm, not hot), the fermentation may be incomplete and you can reheat gently to 60°C and continue. A dehydrator at 60°C also works well.
How long does homemade amazake keep?
Refrigerated in a sealed container: 5 days at full sweet flavor quality. The fermentation slows significantly at refrigerator temperatures (4°C) but does not stop — the amazake will gradually become slightly sourer over the storage period. To halt fermentation and extend shelf life to 10 days, heat the amazake to 75°C for 1 minute before refrigerating. Frozen amazake keeps 3 months — freeze in 150 ml portions for individual servings.
Can I use brown rice (genmai) instead of white rice for amazake?
Yes — genmai amazake is nuttier, earthier, and slightly less sweet than white rice amazake. The bran layer on brown rice slows enzyme penetration, so extend the fermentation time by 2 hours (10–12 hours total at 60°C). The result has more fiber and B vitamins but a thicker, rougher texture. Blend thoroughly for a smooth drink. Some producers specifically make genmai amazake as a more nutritious variant.
What does amazake taste like?
Good amazake has a clean, natural sweetness — not cloying, without any yeasty or fermented tang. The texture is somewhere between thin oatmeal and a sweet rice drink. The flavor is milky-sweet with a faint koji note (earthy, mushroom-adjacent). Warm amazake is more aromatic and sweeter-tasting; cold amazake is more refreshing with the sweetness slightly muted. Thin it with 1:2 or 1:3 water for a drinking consistency, or use it thick as a sweetener in cooking.
Related guides
- What Is Amazake — types, flavor, and where amazake fits in Japanese food culture
- How to Use Amazake — drinks, marinades, sweetener, and cooking applications
- How to Make Koji — if you want to cultivate your own rice koji
- How to Make Shio Koji — koji + salt fermentation for seasoning and marinades
- Fermentation Hub — all fermentation guides and methods