Lacto-Fermented Amazake Soda: A Naturally Sweet & Sour, Umami-Rich Probiotic Drink

Sugar-free koji soda recipe - learn to make healthy probiotic amazake soda with no added sugar

Amazake, a traditional Japanese sweet rice drink, is made by fermenting rice with koji (Aspergillus oryzae). The enzymes in koji break down rice starches into simple sugars, creating a naturally sweet, nutrient-rich liquid. By fermenting this liquid with water kefir grains or ginger bug, we transform it into a fizzy, probiotic-rich soda—without any added sugar.

Unlike commercial sodas or even kombucha, this method leverages koji’s enzymatic power to provide all the sugar needed for fermentation. The result is a well-balanced, tangy drink with a deep umami aftertaste—a signature of koji fermentation.

The Science Behind Amazake Soda Fermentation

This process combines two key microbial actions:

1. Enzymatic Sugar Release (Amazake Stage)

   • Koji’s enzymes (amylase, glucoamylase) break down rice starches into glucose and maltose.

   • Incubate at 50–60°C for 8–10 hours (sous vide recommended for precision).

   • The strained liquid is diluted to 8–10°Bx, ideal for LAB fermentation.

2. Lactic Acid Fermentation (Soda Stage)

   • Water kefir grains or ginger bug introduce LAB (Lactobacillus) and wild yeast.

   • Fermenting at 20–24°C for 3–4 days ensures a robust LAB profile.

   • Final pH drops to 3.5–4.0, delivering a bright acidity and lingering umami depth.

Key Benefits of This Method

✔ No added sugar – Koji enzymes provide all fermentable sugars naturally.
✔ Rich umami complexity – Koji’s proteolytic activity enhances flavor depth.
✔ LAB-dominant – Promotes gut-friendly bacteria over excessive yeast.
✔ Customizable – Fruits/herbs can be added for secondary fermentation.

Note on Water Kefir Grains Maintenance

Water kefir grains require sugar to thrive. After each amazake soda batch, rejuvenate them in a 8% sugar-water solution for 24–48 hours before reuse.

Recipe: Lacto-Fermented Amazake Soda

Ingredients

Amazake Base:

• 500 g rice koji (Aspergillus oryzae-inoculated rice)

• 750 g water or tea (lightly brewed tea or herbal infusion)

Fermentation Starter:

• 1 tbsp active water kefir grains (or 50 ml ginger bug liquid)

Optional for Secondary Fermentation:

• 100 g fruit or puree and/or herbs

Equipment

• Sous vide setup (or warm fermentation chamber – a rice cooker at “Keep Warm” mode)

• Cheesecloth/fine strainer

• Fermentation jar

• Refractometer (for °Bx)

• pH strips/meter

Method

1. Prepare the Amazake Liquid

• Mix rice koji and water/herbal tea in a sous vide bag or jar.

• Incubate at 55°C for 8–10 hours.

• Strain through cheesecloth, pressing to extract all liquid. Discard solids.

• Dilute with water to 8–10°Bx (measure with brix refractometer).

2. Primary Fermentation (Culturing with LAB)

• Combine strained amazake liquid and water kefir grains / ginger bug liquid in a clean jar.

• Cover with a breathable cloth or loose lid.

• Ferment at 22–25°C for 2 days (if using water kefir grains, strain them out after 48 hours)

• Transfer into a sealed bottle and at 20–24°C for 2 more days for carbonation.

• Check pH: Target 3.5–4.0 (tangy and umami-rich).

3. Secondary Fermentation – Optional (Flavor & Carbonation)

• Add fruit/herbs if desired.

• Leave 5cm headspace and seal tightly.

• Ferment at 20–24°C for 2 days, then cold-crash in fridge for 24 hours.

4. Serving & Storage

• Chill before opening to retain carbonation.

• Store refrigerated for up to 3 weeks.

Troubleshooting Tips

• Weak acidity? Extend fermentation by 1 day.

• Overly fizzy? Reduce secondary fermentation time.

Why This Soda Stands Out

Amazake soda is not just another probiotic drink—it’s a harmony of science and tradition. The koji-driven process ensures a perfect balance of sweetness, acidity, and umami, while LAB fermentation adds gut-health benefits.

Ready to experiment? Share your results with us at info@cosmos-society.com or tag us on Instagram @cosmos.society.concepts and explore more koji-based fermentations!

Another amazake-based LAB-driven fermentation:

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Denis Pashkov
cosmos society