Knowledge Base

Amazake

Cultured beverage · Traditional · peer-reviewed

Japan's sweet koji rice drink — Aspergillus oryzae enzymes turn steamed rice into a creamy, naturally sweet porridge you sip warm or chill as a base.

Moderate to make
1 day ferment
enzymes, sugars, amino-acids supplied

Ingredients

  • Cooked white or brown rice (warm, not hot)300 g
  • Rice koji (Aspergillus oryzae on rice)150 g
  • Water, to loosen to a drinkable porridgeas needed

How to make it

  1. Step 1

    Cook rice and cool to about 55–60 °C — hot enough for koji enzymes, cool enough not to kill them.

  2. Step 2

    Crumble in the rice koji and mix thoroughly. Add a splash of water if the mass is stiff.

  3. Step 3

    Hold at 50–60 °C for 8–12 h (thermos, yogurt maker, or oven with care).

  4. Step 4

    Done when the rice tastes distinctly sweet and smells fragrant — starches have converted to sugars.

  5. Step 5

    Blend or mash with water to a drinkable consistency. Serve warm, or cool and refrigerate.

  6. Step 6

    Keep cold and use within a few days. Do not leave at room temperature once sweet — wild yeasts will ferment it further.

What it is

Amazake is a traditional Japanese sweet rice drink made by incubating cooked rice with rice koji (Aspergillus oryzae grown on rice). Unlike kombucha or kefir, the primary work is enzymatic, not a long souring ferment: koji amylases break starch into sugars, yielding a creamy, naturally sweet porridge that is thinned and drunk warm, chilled, or used as a sweetener. A related form is made from sake lees; this recipe is the koji style.

The science

A. oryzae secretes powerful amylases and proteases. At roughly 50–60 °C those enzymes hydrolyse rice starch into maltose and glucose and free some amino acids, creating sweetness and body without added sugar (Allwood et al., 2021 — same koji enzyme system as miso and sake). The short, warm incubation favours enzyme activity over wild microbial souring. Once cooled and diluted, amazake is perishable: ambient yeasts can ferment the new sugars into alcohol and acid if it sits out.

Safety

Use food-grade rice koji and hold the incubation in the 50–60 °C window — much hotter kills the enzymes; much cooler invites unwanted microbes. Refrigerate as soon as it tastes sweet. Discard if it smells sour-rotten or shows mould. People avoiding alcohol should note that further ambient fermentation can produce traces of ethanol.

Signs it worked / troubleshooting

  • ✅ Good: distinctly sweet after 8–12 h, pleasant koji aroma, porridge softens.
  • ⚠️ Stays starchy, not sweet = too hot (enzymes killed) or too cool/short → hold nearer 55 °C for a full overnight.
  • 🚫 Sour or mouldy = contamination or left out too long after saccharification → discard.

How to store

Refrigerate and drink within 2–4 days, or freeze in portions. Warm gently to serve; boiling destroys the fresh enzyme character.

References

  • Allwood JG, Wakefield LT, Grant H, et al. (2021). Fermentation and the microbial community of Japanese koji and miso: a review. Journal of Food Science 86(6):2194–2207. doi:10.1111/1750-3841.15773
  • Kusumoto KI, Yamagata Y, Tazawa R, et al. (2021). Japanese traditional miso and koji making. Journal of Fungi 7(7):579. doi:10.3390/jof7070579
  • Kitagaki H, Kitamoto K (2013). Breeding research on sake yeasts in Japan: history, recent technological advances, and future perspectives. Annual Review of Food Science and Technology 4:215–235. doi:10.1146/annurev-food-030212-182545

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