Incubation temperatureIndonesian tempeh shops don't use incubators but let their tempeh ferment for about 2 days at room temperature, which is around 25°C. In colder climates it is important to incubate tempeh in a special place where temperature can be maintained at optimal level. But what is this optimal temperature? The Book of Tempeh mentions a temperature of 30-31°C for incubating tempeh at home or in a community.
Optimal growth temperatureWe determined the optimal growth temperature of our Rhizopus strain (used in our popular tempeh starter type A) by measuring the growth rate at different temperatures and arrived at below graph. This growth rate is defined by the relative size of one colony after 20 hours of growth on potato dextrose agar.
As you can see from this graph, the optimal growth temperature is 34°C, but growth rate is still high in the range 30-37°C. Below a temperature of 22°C or above 41°C the Rhizopus molds show practically no growth.