Move over, tofu. Tempe — its Indonesian cousin is making its way on more dining tables across the globe. First, it was with the healthy-eating vegan set. Then, it entered the vocabulary of avant garde gastronomy. Places as varied as The Nordic Food Lab founded by Noma’s Rene Redzepi began experimenting with making tempe using heritage Nordic legumes.
The technique itself was born in Java as a byproduct of the tofu-making cottage industry. The Serat Centhini, a compilation of Javanese history, noted that it arose in the early 1600s in the era of the Mataram Sultanate.
Today, tempe is firmly lodged in the Southeast Asian diet and easily available in supermarkets. These are often cultured in plastic bags instead of being swaddled in leaves as they are traditionally done.
It turns out, the vegans are on to something even before tempe became hip. Contemporary research showed that these soy bean cakes are chock full of goodness compared to just eating soy beans on its own. The most commonly cited? An increased bioavailability of soy proteins and higher levels of vitamin B12 (which can’t be synthesised by the human body).
But here’s a cool fact: the tempe that we get today is just one variety. This popular version is known as tempe kedelai (where kedelai means soy beans). Other types include tempe gembus — tempe made from okara, tempe benguk, made from velvet beans and oncom, which is made from the pressed cakes of groundnuts used in oil production.
The remaining one, tempe bongkrek, made of pressed coconut cakes after oil is extracted has been banned as the technique is highly susceptible to contamination.
This variety is only one part of a family of fermented food in the Nusantara’s culinary pantheon. A quick glance into any of the region’s wet markets will reveal a stunning diversity ranging from tapai — fermented tapioca or glutinous rice, to budu — a fish sauce from Northern Malaysia and of course belacan/terasi, slabs of fermented shrimp that will make your food sing with umami. That’s just scraping the tip of the ice berg.
Yet tempe differs because its fermentation technique involves mould (Rhizopus oligosporus or Rhizopus oryzae) rather than just bacteria. In olden times, tempe makers would wrap cooked soy beans in hibiscus leaves (Hibiscus tiliaceus) as this is where the mould’s spores are naturally found.
Those leaves aren’t easy to get these days and you can purchase a starter online if you’d like but seeing how most of the websites operate out of the West, it’s quite frankly, pointless. Instead, here’s a kitchen hack: Use an existing slab of tempe and culture it in ziploc bag. The science behind this is simple: The mould is a living thing and it will reproduce in the right environment.
Alternatively use banana leaves or as pictured below, simpoh air leaves (Dillenia suffruticosa). It’s a plant used in traditional Malay/Indonesian medicine to treat wounds, though contemporary research has shown that parts of the plant is antimicrobial. Could it help ward off microbes that might ruin the fermentation process? Maybe. The plant grows wild in Southeast Asia and if you’re living in Singapore, you might still be able to forage for it. Here’s more.
How to make tempe without a starter
1 slab of existing tempe
1 cup soy beans
4 cups water
3 tablespoons vinegar
Soak the soy beans for eight hours, preferably overnight
Wash the soaked soy beans and dehull them. This allows a larger surface area of the beans to come into contact with the mould.
Boil the beans for 20 minutes. Add the vinegar. This creates an acidic environment for the mould to thrive.
Strain and return it back to the pot on very low heat and continue stirring until it dries.
Allow to cool completely as the next step involves introducing the mould to the cooked soy beans. If the temperature is too hot, you could end up killing the mould.
Tear the existing slab of tempe into small pieces and mix it well into the soy beans.
Place the mixture on the underside of the leaf, or inside the plastic bag. Make sure the mould is spread out evenly. Fold.
As we’re not using a starter, spread the soy beans out in a thin layer so the slab forms faster.
If you’re using a plastic bag, poke holes to allow the mould to breathe. If you’re using a leaf, don’t worry if it tears a little.
Once it’s done, set all of this aside, preferably in a place away from direct sunlight. As no tempe starter is used, it will take an additional day for the mould to spread.
Tempe made this method is usually ready by end of day 2 or even on day 3. At this point, it should have formed a solid block, with a distinct ammoniac smell.
Extra note 1: Do not be alarmed if you see black spots or if the tempe feels slightly damp. It’s still edible.
Extra note 2: Store it in the fridge to stop the mould from growing any further.
Extra note 3: Keep some tempe if you wish to make another batch. Storing it in the fridge will not kill off the mould’s re-growing potential.
Extra note 4: You can incorporate different types of nuts into the mix (I used almonds) but the proportion of soy beans to other nuts must remain 3:1 or the structure will not form.