So how did it turn out? Well, it was a bit "ripe"... We didn't get any photos, but the tempeh cakes were covered in white and black fuzz and smelled strongly of ammonia. The tempeh was mostly salvagable (including our experimental half-turtle bean batch). We cut off the exterior fuzz and fried the interiors until the smell wasn't very noticable.
We're not exactly sure what caused the "ripeness", but it was probably because, at the start, we had trouble maintaining the 85°F required with 6W (oops, I should've done a load calc on the cooler!) so we had to add some Christmas lights for extra heat. This caused the heat to be a bit uneven, so the tops were "done" while the bottoms were not yet solid. Oh well, we'll get better with practice!
As you can see in the before incubation photo below, we used banana leaves as the wrapper, as is traditional in Indonesia. I think next time, we'll try plastic bags because they allow you to check done-ness more easily.
- Make sure you have enough heat to keep the incubator/cooler at 85°F.
- Put heat source at the bottom of the incubator.
- Put tempeh cakes in the fridge to slow/stop at first sign of done-ness, as they'll continue to grow in the fridge until they get cold enough.
- Plastic bags make checking done-ness easier (helpful for inexperienced tempeh makers like ourselves).
- The half-soybean, half-black bean batch worked fine, but the resulting cakes were a bit more crumbly than the all-soybean variety.
The sandwich above is fried tempeh with sauerkraut and a peanut sauce.