Use 2 cups of dry soybeans, soaked in water for 12 hours at room temperature of 65 to 80 degrees F, then massage with hands to split beans and remove hulls. Then rinse well and drain.
Boil the beans for 1 hour then discard cooking water. Dry the beans by patting with disposable paper towels.
Place beans in dry bowl and allow to cool until lukewarm 95 to 98 degrees F. Add 2 tablespoons of distilled white vinegar and mix well. Add 5 grams of rhizopus oryzae culture (Cultures For Health brand) and mix well.
Spread beans to 1 1/2 inches thickness in 10-inch by 11-inch Ziploc bag with 12 small perforations to the top set at 1-inch apart.
Place bag in raw food dehydrator set at 87 degrees F for 12 hours. Verify temperature using k-type hypodermic probe inserted into middle of beans and monitor every 1 hour with thermocouple.
Turn dehydrator off and for the next 24 hours continue to monitor temperature with thermocouple every 8 hours to maintain a range of 85 to 91 degrees F. Turn just fan on in dehydrator if temperature is above, or set temperature to 87 degrees is temperature is below range.
Use immediately or plastic wrap, label/date and refrigerate for up to 3 weeks for later use.