To make tempeh at home you need two ingredients :
- Your favourite beans or grains.
- Certified tempeh culture starter (can be ordered at topcultures.com)
Making tempeh includes 7 steps:
1. Soaking
2. Cooking
3. Drying
4. Dehulling
5. Inoculation
6. Molding
7. Incubation
1. Soaking
Firstly wash the beans then soak them in water throughout the night (6-18 hours). Soaking beans in water softens the beans, which reduces the total cooking time later. Moreover, soaking causes the first stage of pre-fermentation during which the pH level of the beans is lowered. Low pH level inhibits the growth of undesirable bacteria which could later spoil the tempeh and it is still friendly for Rhizopus mycelium to grow.
If the soaking process is skipped more mycelium starter should be used to assure that Rhizopus concentration is greater than that of other bacteria.
2. Cooking
Use vinegar with the cooing water, about 15ml of vinegar to a 1l of water (15ml is around 2 tablespoons). Cooking makes beans ready for incubation and kills most of the undesirable bacteria. Cooking time depends per kind of the beans you are using. Cook beans according to your taste preference with a pinch of salt. Beans have to be cooked until ready to eat or slightly undercooked. Do not overcook the beans as it lowers their nutrition value and mashes them together which would hinder the growth of mycelium.
3. Drying
Dry the beans on a clean towel or paper towels, you can also leave them in a strainer. Beans are ready when the skin of the beans is not shiny anymore. At this time beans wil reach the right amount of moisture. Too little humidity causes drying off of the beans’ surface which stops the growth of the Rhizopus mycelium and encourages the early sporulation which makes tempeh black. Too much humidity creates a perfect environment for unfavorable spoilage bacteria and prevents optimum oxygen diffusion into the beans.
Never start inoculating the beans if they are too warm. Beans should reach the body temperature or lower. Temperature higher than that would kill the Rhizopus culture.
4. Dehulling
You can decorticate the beans by bruising them with your hands. You only need to bruise them a little so Rhizopus culture can easier access the nutritious content inside the beans. This step is important for the beans that have thicker skin like red kidney beans, soybeans, etc. If you work with grains this step can be skipped.
5. Inoculation
Mix Rhizopus culture with prepared beans. For 500 grams you need to add around 2 grams of tempeh starter (approximately one teaspoon). Mix the ingredients very well as even distribution reduces the risk of spoilage. Always mix with a clean spoon, not with your hands. By mixing with hands you lose a lot of the starter culture because it will stick to your hands.
6. Molding
Put the mixture into the desirable mold. Usually, food grade bag is used to produce a tempeh cake. Rhizopus mycelium needs oxygen to grow thus make sure that any mold you are using has access to oxygen. (Without oxygen Rhizopus mycelium suffocates and dies. Tempeh then would be crumbly. Too much oxygen could encourage the drying out of the bean surface and would inhibit the Rhizopus growth. A very slow, uniform diffusion of air is ideal). To assure the diffusion of air poke both sides of the food grade bag with a thick needle. Holes have to be approximately 2cm apart from each other. Close the top of the bag and distribute the mixture evenly. Do not make tempeh thicker than 5cm because oxygen would not reach the centre of the cake stopping it from growing.
Poke the holes in the bag.
Fill the bag and evenly form he tempeh.
7. Incubation
For this step, an incubator or an area with a constant temperature of around 30 °C is needed. Place your tempeh there and let it grow for 28-40 hours.
The tempeh is good and ready to eat if it has a firm white growth and it is evenly grown throughout the tempeh surface (a small amount of dark grey colour is normal, it is caused by mycelium spores that indicate a slight overgrowth). The smell has to be fresh, mushroom-like, yeasty (slight smell of ammonia is normal).
If your tempeh is slimy, has a disgusting smell and colour, toss it in the bin.
Last notes:
NEVER EAT TEMPEH RAW. Tempeh has to be cooked for at least a minute at a minimum of 80°C. After preparing raw tempeh always wash your hands and tools well.
Tempeh can be stored in the fridge for 5-7 days and frozen for three months. If unfrozen tempeh has to be consumed within 3 days.
You can order certified tempeh starter at www.topcultures.com
The starter has to be kept in the fridge and has a shelf life of one year.
Good luck and enjoy!