How to make tempeh with tempeh culture
Jeff and I attended a Tempeh residential in Yogyakarta, the heart of Java - and not only did we learn a lot about making it - we ate tempeh at every meal - fried crisp in sambal, steamed in banana parcels, crumbled into coconut-rich curries. Making your own is probably the only way you'll experience real - fresh tempeh here in Australia - as stores will only stock frozen or pasteurised.
What You're Making
Tempeh is a traditional Indonesian fermented soybean cake bound together by white mycelium from Rhizopus oligosporus cultures. The fermentation transforms cooked soybeans into a firm, sliceable cake with an earthy, nutty flavour and remarkable nutritional density. Unlike many ferments, but as you'd expect with mycellium, (think Koji) tempeh requires temperature control (around 30°C/86°F) and needs humidity. It will develop within 24-48 hours. This is perfect for summer in Australia - you might not even need an incubator!
Ingredients
- 500g dried soybeans (organic preferred)
- 2 tablespoons vinegar (white or apple cider)
- 1-2 teaspoons tempeh starter culture (Rhizopus oligosporus)
Equipment
- Large pot for cooking
- Colander
- Clean tea towels
- Perforated bags (or ziplock bags that you'll poke holes in) or banana leaves - best!
- Incubation setup: insulated box, heating pad, or dehydrator set to 30°C (or a hot muggy day)
- Thermometer
Method
Prepare the soybeans: Soak your soybeans in plenty of cold water for 8-12 hours or overnight. They'll nearly double in size. This step softens the beans and begins breaking down some of the complex sugars.
Dehull the beans: Drain and rinse the soaked beans. Now comes the satisfying part - you need to remove most of the hulls. Rub handfuls of beans vigorously between your palms or knead them firmly in the bowl. The skins will split and float to the surface. Fill the bowl with water, agitate gently, and pour off the floating hulls. Repeat this process several times. Don't worry about getting every single hull - aim for about 90% removal. The hulls can interfere with the mycelium binding the beans together.
Cook the beans: Split the dehulled beans in half by squeezing them gently (this increases surface area for the culture). Place them in a large pot, cover with fresh water, and bring to a boil. Reduce heat and simmer for about 30-45 minutes until the beans are fully cooked but still hold their shape - they should be tender enough to squash easily between your fingers but not mushy. Undercooked beans won't ferment properly; overcooked beans create excess moisture.
Dry the beans thoroughly: This is crucial. Drain the beans well and spread them on clean tea towels. Pat dry and let them air-dry for 20-30 minutes, tossing occasionally. You want them quite dry to the touch - excess moisture is the enemy of good tempeh, encouraging unwanted bacterial growth instead of the desired fungal fermentation. The beans should still be warm (not hot, not cold) when you inoculate.
Acidify and inoculate: When the beans have cooled to body temperature (around 35°C or lukewarm to touch), stir through the vinegar - this lowers the pH, creating an environment where the tempeh culture thrives and competitors struggle. Sprinkle the tempeh starter evenly over the beans and mix thoroughly for at least a minute. Every bean should have contact with the culture.
Pack into containers: Transfer the inoculated beans into your prepared bags or containers. If using ziplock bags, fill them about 3-4cm deep and flatten to create an even layer - this ensures uniform heat distribution. Using a sterilized needle or pin, poke holes every 2cm or so across both sides of the bag. These holes allow the mycelium to breathe (it's an aerobic organism) and release metabolic heat. If using banana leaves, wrap the beans in a parcel tied with kitchen string and pierce holes throughout.
Incubate: Place your packets in your incubation chamber set to 30°C (86°F). The first 12 hours are critical - the culture needs to establish itself before competing organisms can take hold. During this time, you'll notice the bags may fog up slightly from metabolic activity.
Monitor the fermentation: After about 12-16 hours, you'll see the first signs of white mycelium forming, usually starting around the air holes. By 24 hours, the beans should be partially bound together. By 30-36 hours, you'll have a firm cake of beans completely covered in white mycelium. Some grey spotting is normal, especially where the mycelium is very thick. Black spots indicate sporulation - the culture making spores. This is edible but indicates the tempeh is fully mature.
Cool and store: Once the tempeh is firm, bound together throughout, and has a pleasant mushroomy aroma, remove it from the incubator. Let it cool to room temperature, then refrigerate. Fresh tempeh will keep for about a week refrigerated, or you can slice and freeze it for several months.
Troubleshooting
Beans won't bind together: Usually caused by excess moisture, insufficient culture distribution, or temperature fluctuations. Make sure beans are truly dry before inoculating and maintain steady temperature.
Ammonia smell: The beans fermented too long or temperatures were too high. The tempeh is past its prime but still edible if the smell isn't overwhelming.
Yellow or pink colouration: Contamination. Discard and troubleshoot your sanitation and drying steps.
Slow fermentation: Temperature likely dropped below 28°C. Try to maintain 30°C consistently, especially in the first 12 hours.
Variations
Once you've mastered soybean tempeh, you can experiment with other legumes (black beans, chickpeas) or grains (barley, quinoa). Many Indonesian makers blend soybeans with other ingredients. Just maintain similar moisture levels and adjust cooking times for your chosen base ingredient.
The beauty of tempeh is its transformation - you're not just preserving soybeans, you're creating something entirely new, with enhanced digestibility, reduced antinutrients, and complete protein. The mycelium pre-digests the beans while adding its own subtle flavour and nutrition.
