How to Make Koji Rice at Home (Even in Cold Climates!)

Struggling to make Koji rice in the winter? Fermentation requires consistent warmth, and in cold climates, it can feel nearly impossible. In this video, I share my simple but effective space heater hack to maintain the perfect temperature for professional-grade homemade Koji. We walk through the entire process—from steaming the rice to inoculation and monitoring the ferment—so you can succeed even when it's freezing outside. Perfect for Japanese food enthusiasts and DIY fermenters looking for a reliable cold-weather solution. Koji Rice is steamed rice that is inoculated with Koji spores and left in a warm, moist environmentally controlled room to propagate over 2-3 days. The rice becomes covered in a furry white fuzz then spread out to dry for two days. This Koji rice is the most important ingredient for preserving and fermentation The Japanese way like Miso, Sake and all kinds of Japanese pickling. Ingredients • 1 kg Japanese short grain rice (sushi rice white or brown) • 2 g. Koji-kin culture (Koji Spores) • 5 g. Rice Powder (if you don’t have, make your own by grind short grain rice into powder) Instructions 1. Rinse the rice until the water runs clear (to remove all the starch). 2. Soak your rice covered in water for 8-12 hours. 3. Steam rice for 50 minutes 4. 5 g. rice flour toast to kill bacteria we don’t want any stranger, cool 5. Cool rice to room temperature. (105F/40c) flip the rice every 20 minutes we want separate rice dried outside but moist inside. Always wrap the rice with a damp cloth. 6. Mix rice flour with 2g Koji spores, this is called the culture. 7. Thoroughly mix the steamed rice that is now cool with the culture. 8. Spread it out in a baking dish and cover with a damp cloth (to maintain the right amount of moisture), maintain at 90 F (30 C) with high humidity for 48 hours. Add a tray of hot water for humidity in your fermenting station (oven, incubator, heater) 9. After 24 hours, if temperature over 95F, no need to fermented very close to the heater source anymore. temperature will rise themselves during fermented. 10. Move the rice in a shallow tray for easy to stir, cover with damped cloth and fermented 1 more day on the counter. 11. Stir every 12 hours to break up the clumps and evenly distribute moisture. It is finished after 48 hours, when white mold fibers fully developed. (Don't let it go longer than that or it will spore). 12. Dry out for 2 days before pack. 13. Store in the freezer until you are ready to use it. ** The key success factors: maintain temperature at 90F (30C) with high humidity for 48 hours. Because I live in very cold climate, heater only my choice to warm my fermented station. #japanesefood #kojirice #fermentation #Koji #DIY #FoodHack