For a few years now, I’ve been making tempeh because I couldn’t find it for sale in Poland. For the last month or so, I’ve been making it and selling it to the Kooperatwya Dobrze here in Warsaw. This week I documented the process to to show people how tempeh is produced, and also just to assess how much time and money it costs to make.
Making tempeh starts Monday night and ends Thursday morning.
Crack and soak the beans
Of course we start with organic, GMO-free soybeans. 1000 kg of soybeans makes about 1600 g of tempeh. Interesting, huh? That means that 37,5% of tempeh is — well, what is that white stuff exactly? It’s the mycelia of fungi Rhizopus oligosporus and Rhizopus oryzae! (I apologize for referring to then as bacteria and mold in the past.)
The first step is to separate the husks from the beans. The husks must be removed because Rhizopus oligosporus/oryzae cannot penetrate the husk. The husks are separated with a loosely-set grain mill, which cracks them and in so doing removes the husk. If you don’t have a grain mill, you’ll have to remove them by hand after the beans have soaked or you could try to find soybeans that are already de-husked. I have not yet been able to find these in Poland (organic non-GMO de-hulled soybeans).
The beans are put into water. At this time, some of the husks float to the top and can be skimmed off.
The beans are left to soak overnight.
Wash the beans
By morning, the beans have expanded and more husks have floated to the top. These husks are removed. The next step is to partially cook the beans — this means about 30 minutes. As they cook, a foam forms and yet more husks rise to the top and are removed. As you can see, removing the husks is he beans are placed in a colander.
Dry the beans
The beans are spread out on a flat surface on clean lint-free cotton material, such as pillowcases or sheets. It takes at least 4 hours for the beans to dry. Wet beans prohibit the growth of Rhizopus oligosporus/oryzae and encourage other kinds of growth — the kind we don’t want. So it is important for the beans to be completely dry.
Inoculate and pack the beans
By the evening, the beans are ready to be inoculated. All 1000g of beans are placed in a big pot or bowl. To this we add 2 Tablespoons of Rice Vinega and 2 teaspoons of Rhizopus oligosporus/oryzae starter. Any kind of vinegar can be used, just make sure the acidity is no greater than 5% acidity. I once used white Polish vinegar (acidity 10%) and killed the spores. Vinegar creates an acidic environment in which other fungi and bacteria cannot grow.
Next we pack about 500g of the beans into 1 gallon-sized / 3-liter-sized zip-locked bags. The bag has already been punctured with many tiny holes spaced about 1 cm / .5 inch apart. By using zip lock bags, the tempeh can be removed without destroying the bag, and so the bags can be reused many times.
This step takes about 30 minutes.
Incubate the beans
The bags are placed on some sort of rack that has holes or space to create airflow. I use a shelf from Ikea and a rack for drying cookies. These are placed in a box, or some other insulated space with a light bulb — approximatey 40-60 watts usually generates enough heat. We need a fairly constant temperature of between 26-30 C. Lately, I have been using a cabinet in my desk. It’s painted black and does an excellent job holding the heat. The tempeh goes on the top shelf and the light on the bottom. The tempeh is not placed directly under the bulb where it is very hot.
The beans must “cook” for 24-36 hours between 26-30 C. The temperature should be monitored during this time. I no longer use a thermometer (because mine is broken) so I had to develop my Temperature Sense. In this case, the door is nearly closed the first 8 hours and open the rest of the time. It is better to err on the cool side. If the temperature is too high, the spores are killed and the tempeh is ruined. It’s important to have air flow around the tempeh.
The tempeh is done. Each 500g bag of soybeans yields about 820g of tempeh. Removing and sectioning the tempeh takes about 30 minutes. The tempeh is then delivered to the co-op Thursday afternoon.