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! This is one of those protein ferments that you cook - and benefit from the fermentation in a different way - the tempeh is already 'pre-digested' and nutrients more readily available. It's also very delicious.
Jeff and I attended a Tempeh residential in Yogyakarta, the heart of Java - and not only did we take a deep dive in tempeh making in all shapes and sizes and with different mediums, and in very humid weather with steaming pots and frying pans around - we also ate a lot of tempeh - fried crisp as a Tempeh Mendoan with sambal, steamed in banana parcels, crumbled into coconut-rich curries. Our favourite way ~ at the moment ~ is taking a freshly made round block, slicing it and frying it - see below. That's it. Some kecap manis - or even just salt. So delicious. Making your own could be the only way you'll experience that real, fresh tempeh flavour here in Australia - most stores will only stock frozen or pasteurised however you might find a maker at your local market. I know of one up on the northern rivers, one in Hobart and the tempeh here in Melbourne, whilst sold pasteurised for large scale sales - do sell their fresh blocks frozen. However - you still cannot compare that to what you can make at home.
Check out our sausage style shape we made... we also made round, burger shapes and beautiful blocks for slicing.
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
Directions
Prepare the soybeans: Soak your soybeans in plenty of cold water for 8-12 hours - or even better overnight. They'll nearly double in size. This step softens the beans and begins breaking down some of the complex sugars. You don’t have to do this, but it cuts down cooking time - and presoaking beans is in general, a good practice. Also - if you’re soaking them in warm temperature, some fermentation will take place, lowering the pH already - so that you don’t really need to add vinegar when you innoculate with the culture. (this photo is of Jack Beans in Java, not soybeans)
Cook them in plenty of water by simmering for about 20 minutes until the hulls start to loosen and the beans are partially cooked but still firm. There are many ways to do this and we have seen lots of various de-hulling machines - but when you are only making a small batch - hand de-hulling is absolutely fine.
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. Traditionally, this was done in a river - with moving water taking the hulls away. The picture here is of us helping to dehull Jack Beans in Java.
Cook the beans again: 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 45-60 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.
The beans still feel loose as you're putting them into the bags, almost feels like.. how is this going to work? If you look carefully you'll see there are lots of little holes in the bags in the first photo.
You can do this yourself...below is the tool that one of the producers used.
With this burger shape - we used silicone mats to cover the tempeh to keep it warm and not dry it out.
One of the producers we visited used Jack beans and teak leaves - if you can get banana leaves do it! Much better than plastic!
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.
This is no longer a fridge - but an incubator - you can fashion one yourself in containers with heat mats or hot water bottles etc. Setting ourself up with a little incubator sure does make it easier. At home, we have a small insulated locker we made for our koji, and an old bar fridge we use for other things. But a hot and humid day can also work - that is the natural environment of tempeh.
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.
Our blocks were beautiful and strong
The Jack beans in teak leaves after a couple of days.
Sliced and fried in a bit of oil.
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 - Beyond Soybeans:
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 or use other stronger beans and wild rice. Just maintain similar moisture levels and adjust cooking times for your chosen base ingredient.
Black beans (sweeter, earthier flavour)
Chickpeas (nuttier, firmer texture)
Split peas (traditional in some regions)
Mixed beans and grains (adding barley, rice, or quinoa creates interesting textures)
Lupini beans (if you're in WA, these make excellent tempeh!)
Marinate in: tamari, smoked paprika, maple syrup, liquid smoke
Fry until crispy
Crumbled for Bolognese or Tacos:
Crumble or pulse in food processor
Sauté with onions, spices
Add to tomato sauce or taco filling
Grilled Tempeh Steaks:
Cut into thick slabs
Score the surface for marinade absorption
Marinate in your favourite flavours
Grill or BBQ until charred
Indonesian-Style (how it's traditionally eaten): see Tempeh Mendoan
Cut into chunks or thin slices
Deep fry until golden and crispy
Serve with sambal and rice
Quantities & Flavour Ideas:
Basic Marinade Formula:
3 tablespoons tamari or soy sauce
1 tablespoon rice vinegar or lime juice
1 tablespoon maple syrup or honey
1 teaspoon grated ginger
1 clove garlic, crushed
Optional: sesame oil, chilli, herbs
Storage of Finished Tempeh:
Fridge: Up to 7 days wrapped in paper or breathable container
Freezer: Up to 3 months (slice before freezing for easy use)
Fresh tempeh continues to ferment slowly – small black spots are just spores developing.
Need a Break? That's Completely Fine
Your tempeh culture will keep for months in the pantry, however I tend to keep mine in the freezer. There's no pressure to make batch after batch – just store it away and it'll be ready when you are. Life gets busy, and your culture understands.
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.
When your tempeh is good - it can easily handle you cutting it into very thin, almost paper thin slices and then a quick dip in a fragrant, loose batter. You then fry it until the edges are lacy and crisp. aha and whilst people in the west associate tempeh with vegan eating and therefore alternative healthy eating - Tempeh Mendoan is not really that - it's a deep fried snack.
