Tempeh Incubation

Tempeh is a soybean cake bound together by Rhizopus mold, and getting it right depends on holding a narrow temperature band long enough for the mycelium to fully knit the beans without overheating and killing the culture or inviting bacterial contamination. Target Temperature here is a fixed 88°F (31°C) -- the middle of the commonly recommended 85-91°F range for tempeh fermentation, and it does not change with any of your inputs, since it's the goal every other output is built around rather than a per-scenario calculation. Incubation Time starts from a base figure by Bean Type -- 32 hours for soybean, 36 for chickpea, 30 for black bean, reflecting real differences in how quickly each bean's surface supports mold growth -- then adjusts for Incubator Type efficiency (a cooler with a heating pad holds temperature most precisely at 100% efficiency; an oven with the light on and a dehydrator are both treated as slightly less consistent) and for how far Ambient Temperature sits from the 88°F target, which lengthens the incubation estimate whether the room runs cold or hot relative to that target rather than only in one direction.

Vent Check At flags roughly 55% of the way through incubation, the point by which fermentation is generating its own metabolic heat and the bag should be checked and vented if it's running warm -- published home-fermentation guidance similarly warns that tempeh needs monitoring and venting once internal temperature climbs past about 95°F, since excess heat can kill the mold or favor unwanted bacteria over Rhizopus. What this doesn't replace: an actual thermometer probe in the incubation space (ambient room temperature is not the same as temperature inside a tightly packed bag of fermenting beans), and it assumes standard soybean tempeh preparation -- proper acidification of the soak water and full bean cooking are food-safety steps this calculator does not check.