- 4 qt. Cooking pot
- Large clean cotton terry towel
- Measuring spoon
- Metal mixing spoon
- Large mixing bowl
- Room thermometer
Plastic bag: Place two 6” x 8” Ziploc bags (quart size) on top of each other on several layers of thick clean towel. With a clean straightened safety pin, poke holes in both bags every half inch in a grid pattern. Divide the beans evenly between the two bags. Cover the cookie sheet with two layers of thick terry towel and set the bags on them flat. Pat beans firmly into an even layer making sure they fill the corners of the bags.
Cake pan: Pack beans in an even 1/2” deep layer in a very clean, oil-free 9”x13” cake pan. Cover with aluminum foil and perforate every inch in a grid pattern with a safety pin.
Incubators: A tempeh incubator should maintain a temperature of 85°F for 26-30 hours (85°-93° is best). Don’t incubate in anything small or airtight because the culture needs oxygen to grow and some “breathing space” to discharge excess heat and humidity. A couple of practice runs with only a thermometer in your incubator before making tempeh is a good idea to check for temperature fluctuations that may cause problems.
You can incubate tempeh in a warm place in your home. A closet with a drop light, a place where heat collects, such as a high kitchen shelf or warm attic.
Or you can make a simple incubator. Get a Styrofoam cooler with the long sides slanted inward at the bottom. Your tempeh containers should fit wedged in so that the bottom of the tempeh containers are about 3 inches below the cooler’s rim. The two long sides should firmly support the tempeh container, leaving a gap at either end for air circulation. Tape the room thermometer to the center inside lid of the cooler. Place a heating pad in good condition flat on the bottom of the cooler. Run the cord out through a small cut in the rim so the cooler lid sits down flat. For safety and to avoid overheating, do not fold the heating pad over on itself and keep the cloth cover on at all times. Make sure the tempeh container is firmly supported and can’t fall down on the heating pad. Keep the incubator in a safe place away from household traffic, children, pets, and toxic or flammable materials.
Now turn the heating pad on to the proper setting. The setting for the cookie sheet may be higher than the setting for the cake pan. Securely place in your tempeh container. You’ll need to check the temperature often until you become familiar with how your incubator responds to the heat produced by the growing tempeh and variations in room temperature. At room temperature of 65°-72°F you may need to turn off the heat and possibly crack the lid a little at 18 hours. At 73°-80°F you may need to do this at 15 hours. An automatic timer used to turn off lights and small appliances can be used to help control your incubator. When incubation is finished, be sure to turn your incubator off, as you would any small appliance. Disassemble it for added safety.
2 ½ cups dry soybeans, split and hulled
1 tsp. tempeh starter
2 Tbsp. vinegar
- Cook the split soybeans for 1 hour at a bubbling boil, skimming off any bean skins that float to the top. (If a small amount are left, that’s okay).
- Drain off excess moisture, then knead the beans in a towel until they are surface dry. Put the beans in a dry bowl. Having the beans too wet is the most common cause of a bad batch.
- When they are cooler than skin temperature, add the vinegar and mix very well. Then add the starter and mix very well. Unused tempeh starter keeps best when stored in a waterproof container in the freezer.
- Lightly pack a 1/2” dep layer of beans into tempeh container as described above.
Growing the Tempeh:
Prepare your incubator as described above. Set your tempeh container in the incubator. To give it a good start, make sure it’s warm enough the first 12-15 hours. The first sign the tempeh is starting to grow is that the beans lose their shine and start looking dull. At 12-15 hours moisture starts condensing on the inside of the tempeh container, and white fluff begins to show faintly on the beans. The tempeh is now producing heat so check the tempeh occasionally and adjust as necessary. The white fluff gets longer and thicker and almost covers the beans by 17-20 hours. At 24 hours the beans will be almost invisible under the fragrant white mycelium and the cake will be firm and dense. Gray or black spots usually form around the pinholes in the plastic bag. These are the natural result of sporulation and indicate ripeness and flavor. Between 26-30 hours the cake becomes extremely dense, tightly woven by luxuriant threads of mycelium and resembles the flesh of a mushroom.
After 26-30 hours at 90° the tempeh looks like white icing on a cake. It’s done when it is cottony white, marbled with dark gray. Gray or black areas are natural results of sporulation (when mold forms its “seeds”) and are not harmful. In the last part of the incubation, the tempeh gets most of its flavor, so be sure to let it grow long enough.
Checking the tempeh:
Good tempeh – the beans are solidly bound into a white cake marbled with gray or black. Fresh tempeh smells good, like bread dough or fresh mushrooms. It may smell faintly of ammonia. A thin slice of tempeh holds together without crumbling. The mold completely fills the spaces between the beans. It smells good, and feels solid underneath.
Unfinished tempeh – The mold is usually pure white with no gray areas. The beans are bound together loosely and the mold doesn‘t fill the spaces between the beans. It crumbles when sliced. Unfinished tempeh doesn’t have much flavor when cooked and the beans are a little crunchy. Uneven heat distribution may cause part of the batch to finish late. If this occurs, cut off the finished part and let the rest go longer.
Inedible Tempeh – It smells unpleasant or strongly of ammonia. It may be sticky or slimy all over or in spots. The mold may grow only in patches or not at all. Or it may be well-molded on top, but sticky and unpleasant-smelling underneath or in the middle. If the beans aren’t dry enough, the excess moisture settles to the bottom and the beans spoil. When pinched, the cake feels mushy or falls apart. Any other color besides white, black or gray tempeh should be thrown away.
After the tempeh is finished incubating it should be cooled to room temperature, then kept refrigerated (3-4 days) or frozen until used. The fresh cakes shouldn’t be stacked on each other until they are well frozen or they could overheat and spoil.
If desired, the fresh tempeh may be cut into squares and steamed on a rack above rapidly boiling water, covered, for 20 minutes. Cool and repackage into a new plastic bags before storage.
Always cook tempeh thoroughly before eating it to inactivate the culture and other microorganisms and to make it more digestible.