Lights Out Tempeh Maker


My tempeh making has evolved over the years. I have gone from NO-TECH to LOW-TECH. Next I will completly automate my Tempeh Maker. HIGH-TECH!







Make Tempeh without a Temperature Controlled Incubator

Tempeh is a highly nutritious fermented soybean food from Indonesia. It has a somewhat nutty flavor and a firm texture. To make tempeh at home all you need are beans, some tempeh starter culture, and a warm environment. If you live in Indonesia the warm envirnment  is not a problem, but in my house, it is. You can make tempeh at home without a temperature controlled Incubator, or even electricity, if you can heat water. You can use a 48 Qt. Insulated Picnic Cooler and a flat top Six Pack cooler. I used Coolers from Rubbermaid (Victory 48-Quart Cooler 3-Piece Value Pack---$40).  I made the 48 Qt Cooler Super Insulated by inserting 1"  foil faced insulating  foam board  arround the inside of the sides of the Cooler. You will also need  a calibrated thermometer. 


Super Insulate  the Cooler



The Cooler in a Cooler



Fill the Insulated Six Pack Cooler filled with 7 1/2 quarts of 134'F (57'C) water. The hot water will bring the temperature of the 48 Qt. Cooler up to 91' F (33'C), from room temperture, in about 2 hrs. The Hot Six Pack Cooler will slowly release its heat into the Big Cooler over a period of hours. Because of the super insulation, the temperature will only slowly decay for 10 to 15 hrs. Then the growing mold in the tempeh will begin producing its own heat. The Cooler temperature should max out at 91'F (33'C). The fermenting tempeh will hold the beans at 89-90' F (31-32'C) for 36 to 48 hrs. You will need to experiment with the starting water temperature to get the temperature range of the 48 Qt Cooler correct. Do not exceed 91'F (33'C) for the initial temperature.  After 30 hrs, start checking the tempeh every couple of hours. Open the cover,quickley check the tempeh, and close the cover. Don't leave the cover open to long, the box  will cool quickly.  The beans should be covered with white mycelium. When you see dark gray mold spores around the vent hole, the bag of tempeh is mature and ready for harvest.



  1. Measure 2 cups of dry soybeans into a large pot. Cover with water and boil for 30 min. Remove the pot from the heat and allow to cool for 2 hrs.

  1. cooking

  2. Cook the Beans
  3. Strain out the water. Use your clean hands to squeeze the beans through your fingers. Don't be gentile, you need to split the beans in half and loosen the seed coat. A potato masher will also do a good job. Flow cold water into the pot of split beans. Create a whirlpool of water. The seed hulls will tend to float in the moving water. I used a hose clamped along the edge of the pot to create a vortex. Use a strainer to skim the hulls out of the water. Give the beans another squish with the potato masher and repeat skimming. Repeat the process until you get most of the hulls skimmed off. It doesn't have to be perfect.whirlpool(2)

  4. Skim the Seecoats
  5. Cover the beans with water in pot. Add 2 Tbs of White Vinegar. This insures an acid  environment to make the tempeh spores happy. Boil the de-hulled beans for 30 min. Skim off any hulls that pop up. Strain the beans and return them to the hot pot. Stir constantly until the beans are dry. The surface of the beans should look dull. Remove the beans to a dry towel and give them a good rubdown. This is a critical step, if the beans are to wet the tempeh starter will not take and the batch will fail. Transfer the beans to a large mixing bowl. Use the thermometer to measure the temperature of the beans. Wait until the bean temperature is below 85'F (29'C). Don't rush, high temperature will kill the mold.

  6.  cooling(2)

  7. Cooldown
  8. When the beans are cooled to 85' F, sprinkle 3/4 t of tempeh starter evenly onto the beans. Mix the starter into the beans thoroughly Spoon the beans into a 1 Gallon ZipLoc plastic bag. Spread the beans out evenly on a flat surface. Be sure to push them into the corners.

  9. Use an large needle (or small nail) to vent both sides of the bag. Punch holes every 1/2 inch (1 cm) . You need to allow air into the tempeh.

  10. vent(1)

  11. Perforate the bag
  12. Fill the Six Pack Cooler  with 134'F (57'C) water. Close the cover and place it in the bottom of the 48 QT Cooler. The hot water will bring the temperature of the big cooler up to 91' F (33'C) in 2 hrs. or so.

  13. Set the cooling rack on top of the Six Pack Cooler in the 48 QT Insulated Cooler. Place something, like cardoard on top of the Sixpack Cooler to prevent direct contact with the Ziploc bag. Place the bag of beans on the cooling rack, close the cover and go away. Don't cheat and look in on the beans, you will mess up the temperature. Come back in 30 hrs and start checking your tempeh.finished(1)

  14. Finished Tempeh




Material List:


Rubbermaid  Coolers-Victory 48-Qt Coolers  Value Pack --$40


1" Foil Faced Insulating  Ridged Foam-Dow Super TUFF-R-6.5     Homedepot


 Duck Tape  




10" x 10" Kitchen Cooling Rack


1 gal Ziploc bag




Tempeh Starter Culture - Cultures for Health                                                                                                                  





Paul's Electric Tempeh Maker PTM-6



Tempeh Maker




Tempeh making process is long (3 days) and somewhat labor intensive procedure. While I can't make it go faster, I can get most of the work done electrically. It will produce a 16 oz. batch of tempeh,without using plastic bags. I tried to combine as many operations as possible.My Electric Tempeh Maker is built from a modified Black & Decker 16 Cup Rice Cooker/Steamer, and a controller box containing a peristaltic pump, a reversing control switch, a 12 volt power supply and a plastic storage container. The “WARM” temperature in the Rice Cooker chamber is set by an adjustable thermostat. The temperature is set to 88' F (30' C), using an accurate thermometer. The drained soak water is stored in a  Purex Laundry Detergent100 oz. container. Water is drained from the pot and air is injected into the pot, by a low volume peristaltic pump. The slight air flow provides the necessary oxygen for fermentation and also keep the chamber at a slight positive pressure. This will exclude entry of wild mold spores and bacteria.The inside the cap of the storage container has a 50 ml tube with a plastic dip tube attached to it.This allows a small amount of water to be injected back into the pot to provide humidity during incubation.The Rice Cooker/Steamer still can be used for its original purpose.



Disasembled Tempeh Maker


Mill the Beans:

I use a Chrona type grain mill to crack the soybeans. The mill spacing is adjusted so that so each bean is cracked into 2 to 4 pieces. Mill 1-1/4 cups of dry soybeans. If you don't  have a grain  mill, there is a squishy wet method for cracking the beans. It's  messy!


You can separate the seed coats from the cracked beans. You can build a simple winnowing box. Another easy method I have used  is to pour the beans into a container in front of a fan. Do it 4 or 5 times to get most of the seed coats blown off. It's best done outside.Transfer the cleaned beans to a large mixing bowl.


The Mill in the Winnow


 Add Brown Rice:

Add 1/4 cup of brown rice to the bowl and mix the beans and rice. Place the fine mesh plastic disk into the steamer basket. Transfer the mixture to the Steamer Basket and use the 1/4” perforated Plexiglas disk to level and tamp down  the mixture. Just tamp out any air pockets and level the beans. Leave the Plexiglas top in place.

Soak Beans 10-24 hrs:

Adjust the soak time to fit your sleep/work schedule. Fill the cooker pot to level 7 on the Brown Rice scale. Add 1/4 cup of white vinegar to the water. Slowly insert the steamer basket into the cooker bowl. Carefully thread the dip tube through the plastic fitting into the center holes in the basket. Allow 10 to 24 hrs. soak time. You can skim off any seed coats that float up.

 Drain the Beans:

Set the Pump Controller Switch to DRAIN. Allow 40 min to draw down the water in the pot. Turn off the pump. 1-1/3 cups of water will be left in the pot.


Cook the Beans and Cool:

Plug in the cooker and flip the cooker switch to “COOK”.  The beans will steam cook for 40 min, The cooker will automatically trip the switch to the ” WARM” when the water boils off. Allow 5-6 hrs for the beans to cool down.

Dry the Beans:

When the temperature of the beans gets below 95 degrees F you can transfer then to a large metal mixing bowl. Stir to dry the surface of the beans. If your in a hurry you can use a hair dryer.Don't cheat, this is a critical step. The surface of the beans mustbe dry. The beans should have a dull matte finish. You can be sure by dusting the beans with rice flour. This will absorb any remainning water on the the bean surfaces.


Add the Tempeh Starter and mix the beans thoroughly. Transfer the beans back into the steamer basket. Replace the Plexiglas weight. Use the weight to tamp down and level the beans. Replace the cover and dip tube. Switch the pump “AIR”.


Incubate at 88 degrees F (30 C). After 12 hrs, you can turn off the power to the cooker. The fermentation will produce it own heat. Rotate the top knob to wipe the condensation off the bottom of the glass cover. Start checking the tempeh at 24 hrs. When you
see gray spores forming around the vent holes in the Plexiglas weight your tempeh is done.



The next project is to automate the Tempeh Maker by adding an Arduino micro controller to provide the sequencing and timing.



Paul Pepin