Amazake is a thick, naturally sweet Japanese drink made from rice and koji – rice grown with the mold Aspergillus oryzae. Held warm for several hours, the koji’s enzymes turn the rice starch into sugar, so amazake is sweet without any added sugar. It’s drunk warm in winter, chilled in summer, and used as a natural sweetener in smoothies, porridge and desserts.
Two Kinds of Amazake
According to a review of amazake’s ingredients and safety (Kurahashi, 2021):
- Koji amazake is made from rice koji and water (often with extra cooked rice). Its sweetness is glucose released by the koji’s amylase. It is non-alcoholic – the kind this recipe makes.
- Sake-kasu amazake is made by dissolving sake lees (the solids left from sake brewing) in water with added sugar. It contains a small amount of alcohol.
Koji amazake has a long history – it appears in the eighth-century Nihon shoki – and by the Edo period it was sold by street vendors and drunk in summer to fight heat fatigue (Kurahashi, 2021).
How It Works: Enzymes, Not Bacteria
Koji amazake is not a lactic ferment. It is enzymatic saccharification: the mixture is held at 50–60°C (122–140°F), where the koji’s amylase works well. In a controlled study, glucose production peaked at 50°C and was still over 90% of that peak at 60°C, but dropped off at 40°C and 70°C (Oguro et al., 2019). The heat also matters for safety: the review notes that food-poisoning bacteria grow best around 40°C, so holding the mixture at 50–60°C keeps them in check, and finished amazake should be kept below 10°C (Kurahashi, 2021).
Because of this, amazake isn’t a source of live probiotic bacteria. It’s a sweet, easily digested rice drink.
Making Amazake at Home
The full recipe is in the recipe card above. The only tricky part is keeping the temperature in range for several hours – a rice cooker on its “keep warm” setting with the lid ajar, a thermos, or a yogurt maker all work. Use a thermometer: below about 50°C sweetening is slow, and above 60–65°C the enzymes start to be damaged.
Thermos method
Mix freshly cooked rice, koji and water at about 60°C, pour into a preheated wide-mouth thermos or jars, and wrap well. Check the temperature every couple of hours and top up the surrounding water bath with hot water if it drops below 50°C. Taste from around 6 hours; it’s ready when clearly sweet.
Flavors and Uses
- Classic: warm, with a little grated ginger.
- Citrus: chilled, with yuzu or orange zest.
- Matcha or cocoa: blend in 1 teaspoon of matcha or 1 tablespoon of cocoa for a dairy-free latte.
- As a sweetener: use smooth amazake in place of sugar in smoothies, porridge, dressings and baking.
Troubleshooting
- Not sweet after 6 hours: the temperature was probably too low; bring it back to 55–60°C and continue.
- Sour or alcoholic smell: it spent too long at a lukewarm temperature and other microbes took over. Discard it.
- Too thick or too thin: thin with hot water when serving, or use less water next time.
- Separation after chilling: normal – stir or blend.
What About Health Claims?
Amazake is often promoted as a health drink. The human evidence is limited: a randomized, placebo-controlled trial found that koji amazake increased bowel-movement frequency in healthy adults (Kurahashi et al., 2021), and a small trial reported limited effects on skin moisture – both funded by an amazake maker and run by its employees. Other studies have been small and uncontrolled. Enjoy it for its flavor; it is sweet, so count it as sugar if you’re watching your intake.
Other koji and rice ferments: shio koji, Korea’s sweet rice drink sikhye, Chinese jiu niang and Indonesian tapai – the last two are yeast-fermented and mildly alcoholic.