Fermenting At Home: Tempeh

Making tempeh is one of those projects that demonstrates how amazing home-fermented food can be when measured up against its pasteurised, store-bought alternative.

Making tempeh is one of those projects that demonstrates how amazing home-fermented food can be when measured up against its pasteurised, store-bought alternative.

The aroma of a freshly grown batch of tempeh is incredible – floral, aromatic and mushroomy, and will differ depending upon the ingredients you use to make your tempeh. Making it is remarkably simple, provided you have the ability to keep a tray of tempeh at a stable temperature for around 40 hours. That is because the spores of the fungus Rhizopus oligosporus need a nice warm environment in which to grow and colonise the material that you are inoculating.

Very much an artisanal process, because every legume or grain that you use to make tempeh – and the options are very broad and varied – will grow in a slightly different manner. So not only is it important to be disciplined about hygiene and keep a keen and watchful eye on the process, it’s also important to understand that not all batches will be successful and to not be put off if one fails.

tempeh
Much like tofu, tempeh will absorb the flavour of whatever it’s cooked in. Photo by Blair Lucas

Keep It Interesting

Traditionally, tempeh is made from pure soybeans, but there are more flavoursome and visually-stunning combinations of grains and legumes that can be used to make tempeh. The important thing is to make sure that the Rhizopus oligosporus spores can penetrate the ‘skin’ of the substrate to feed on the germ, which means either removing the skin, or chopping the cooked legume or grain to let them in.

When using soybeans you need to first boil them, then laboriously remove the skins by running the soybeans between your fingers. It is time consuming, and while the results of homemade soybean tempeh far exceed store-bought tempeh, it’s easier and more interesting to experiment with other legumes and grains that don’t need skinning. It is also important to consider the size of the legumes you are using – you want to have the least amount of space between each bean or grain as possible, so that the Rhizopus oligosporus has less trouble colonising the entire batch. So if you are using a big legume like a butter bean, you might want to consider adding a smaller bean or grain like quinoa to fill the gaps.

What You’ll Need

When it comes to maintaining a stable temperature for the period of time required to make tempeh – there are a couple of options. The easiest and most accurate way is to invest in a sous vide wand that can be used to keep a water bath at a stable temperature. With this option, you press the inoculated legumes into a cookie tray, then float it in a tub of water which the sous vide wand ensures stays at a steady temperature. The other option is packing the legumes into ziplock bags, pricking them all over with a skewer and placing in an oven that is set at the lowest temperature with the door hinged open.

Using the water bath method you’ll need a sous vide wand, a plastic tub with an appropriate sized hole in the lid to allow the wand to be inserted into the water, two metal or glass baking trays and two medium-size saucepans. You’ll also need a tea towel, a silicone spatula, a large sieve and a hair dryer.

Tempeh Starter

You can make your own tempeh starter but to do that you need to get your hands on some fresh tempeh. Often, but not always, commercially available tempeh has been steamed to stop the mould from sporing which means you’ll have little success in creating the culture. Again, for ease and accuracy, it’s advisable get your hands on a small packet of tempeh starter to kick off your tempeh-making journey.

Before You Start

First, take all equipment and wash it thoroughly, especially the plastic tub and sous vide wand. You do not want any nasty fungus or bacteria getting involved in this process. Then sterilise the baking tray, spatula, large sieve and large glass or metal baking tray (and any other miscellaneous kitchen equipment you might be using) with boiling water.

While not a traditional soybean recipe, the below method will work regardless of the type of legumes and grains you choose to include. By using chana dal, which are basically skinned chickpeas, it’s negating the requirement to skin the legume. As well as adding great flavour, the quinoa is perfect for filling up all the little gaps that exist when chickpeas are used, therefore ensuring greater success.

The Final Piece

Once you’ve finished making your tempeh, it’s important to remember you’ve made a healthy raw product that needs to be cooked before consuming. Because it’s been fermenting for a couple of days in warm environment, as well as all of the healthy bacteria that’s grown, there’s always a chance there’s some unhealthy stuff present too.

There’s myriad ways to cook and prepare tempeh, but steaming and frying are popular choices if you’re eating it by itself.

tempeh
koji
tempeh

Clockwise from top You can soak tempeh in a flavoured brine before cooking; This is Koji, the Japanese version of Indonesia’s tempeh. It uses the same process, just a different fungus to inoculate the soybeans; Tempeh with Thai basil and sambal; Tempeh made from farro and mung beans. Photos by Blair Lucas

Chana dal and quinoa tempeh

INGREDIENTS

400 g chana dal (dry weight), soaked for eight hours
100 g quinoa (dry weight)
2 tbsp white vinegar
1 tsp tempeh starter

METHOD

Preheat your water bath to 31 ºC. In plenty of water and in seperate saucepans, boil the chana dal and quinoa. The chana dal will take around 15 minutes to become tender, while the quinoa will take around 20 minutes to cook. You’ll know it’s done when the little sprout appears and it is tender to the bite. Drain both thoroughly together in the large sieve.

Once the chana dal and quinoa have drained well (approximately 10–15 minutes), transfer into the large glass or metal baking tray and add the white vinegar. Then, with your hair dryer set on the lowest fan setting but the highest heat, gently mix the vinegar with the legumes while slowly drying them. The vinegar is included here to ensure the legumes are fully sterilised prior to adding the tempeh starter. What you are looking for here is a final product that is just a little damp. If it’s too wet the tempeh will turn into a mush, but if it’s too dry the tempeh spores cannot grow. When it’s right, you should have around 1350 grams of mixed legumes.

Once this has been achieved, sprinkle the starter over the legumes and mix through thoroughly. Then press the mixture into the sterilised cookie tray, gently float it in the water bath and cover with the lid.

Take a peek every 12 hours or so to see how it is progressing. You’ll find the first growth sets in at around 18 hours, and it takes around 36 hours or so for it to be finished. When it is ready the entire mass will be covered in white fungus, and will have a strong fruity/mushroomy flavour. Be careful not to grow the mixture for too long – it will turn green or black if you over ferment, which is the tempeh spores sporulating. You can still eat it at this stage, but it will not be as nice as the perfect white tempeh you’re aiming for.

If you went for the pricked bag option, you can place these directly into the fridge, or turn out the finished square of tempeh from the baking tray, cutting into appropriately-sized slabs, before storing it in the fridge until you’re ready you cook it.

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