Growing Protein, Binding Culture
Introduction
Tempeh is one of the most elegant examples of fermentation doing exactly what it is meant to do: transform simple ingredients into something nourishing, stable, and deeply satisfying.
Originating on the island of Java in Indonesia, tempeh developed as a way to preserve soybeans in a warm, humid climate where spoilage was otherwise inevitable. Instead of relying on salt or acidity, tempeh uses a mold, Rhizopus, to bind cooked legumes into a firm, sliceable cake. The result is a food that is rich in protein, highly digestible, and structurally versatile.
Unlike many ferments that hide their microbes, tempeh makes its organism visible. The white mycelium that grows through the beans is not a byproduct. It is the structure itself. Tempeh is not beans plus mold. It is a new organism formed by their collaboration.
In this workshop, we explore tempeh not as a meat substitute, but as a fermentation in its own right. One that sits somewhere between bread, cheese, and mushroom culture.
A Short History of Tempeh
Tempeh has been made in Java for at least several centuries. Early records suggest it emerged alongside tofu production, using the leftover soybeans that were less suited for curdling. Instead of discarding them, producers cooked, dehulled, and inoculated the beans, then wrapped them in banana leaves and left them to ferment.
The mold responsible, Rhizopus oligosporus, thrives in warm, oxygen-rich environments. Banana leaves were not just packaging. They regulated humidity, allowed airflow, and introduced beneficial microbes. Over time, tempeh became a daily food, eaten fried, grilled, or simmered in stews.
Only in the twentieth century did tempeh travel beyond Indonesia, first through Dutch colonial routes, later through vegetarian and fermentation movements in Europe and North America. Today, it is often framed as a protein alternative. In this workshop, we bring it back to its roots as a cultural, microbial, and culinary craft.
What Tempeh Actually Is
Tempeh is a mold fermentation. This makes it fundamentally different from lacto-fermented foods like kimchi or sauerkraut.
The mold produces enzymes that break down proteins, fats, and complex carbohydrates in legumes. This process increases digestibility, reduces antinutrients such as phytic acid, and creates a nutty, savory flavor.
As the mycelium grows, it physically binds the beans together. This is why properly made tempeh can be sliced, grilled, or crumbled without falling apart. The fermentation does not soften the structure. It reinforces it.
Tempeh requires oxygen. It does not ferment submerged or sealed. Airflow, temperature, and moisture all matter. This makes it a precise but very readable fermentation. When conditions are right, the mold grows evenly and smells fresh and mushroom-like. When something is off, you can see it quickly.
Ingredients and Substrates
Traditionally, tempeh is made from soybeans. In this workshop, we start with orange lentils to understand the classic method before expanding outward.
We also explore alternative substrates such as chickpeas, lentils, split peas, and mixed grains. Each substrate behaves differently. Size, skin thickness, and protein content all influence how the mold grows and how the final tempeh tastes and holds together.
You will learn why dehulling matters, why uniform size is important, and how moisture content affects mycelial binding. Tempeh teaches precision without requiring advanced equipment.
The Fermentation Process
Tempeh fermentation happens in three main phases.
First comes preparation. Beans are soaked, cooked, and dehulled. This removes barriers for the mold and creates the right texture. Beans should be tender but intact, and surface-dry before inoculation.
Second is inoculation. A small amount of tempeh starter introduces Rhizopus spores evenly throughout the beans. Distribution matters more than quantity.
Third is incubation. The inoculated beans are packed loosely to allow airflow and kept warm, usually between 28 and 32°C. Over 24 to 48 hours, the mold grows, heats itself, and binds everything into a solid cake.
You will learn how to read temperature, smell, texture, and growth patterns, and how to intervene if things move too fast or too slow.
Step by Step: Start Your Own Tempeh at Home
Tempeh is not a jar ferment. It is an oxygen-loving mold culture. The goal is simple: cook legumes, reduce surface moisture, inoculate with Rhizopus starter, then incubate warm with airflow until the mycelium binds everything into a cake.
The two most common reasons tempeh fails are too much moisture and too little oxygen. If you manage those, tempeh becomes very reliable.
What You Need
Ingredients
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500 g orange lentils (for the workshop version)
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Or 500 g mixed legumes (see options below)
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Tempeh starter (Rhizopus spores), dose depends on brand, usually 1 to 2 g per kg cooked legumes
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White vinegar or kombucha vinegar, 2 tablespoons per 500 g cooked legumes
This helps lower pH and protects the culture at the start -
Optional, a pinch of salt for flavor only
Tools
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Large pot
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Colander
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Clean towel or tray
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Spoon or clean hands for mixing
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Freezer bags or zip bags, or parchment and a clean cloth
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Toothpick or skewer for holes
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A warm spot in the house
Version 1: Orange Lentil Tempeh (Fast and Beginner Friendly)
Orange lentils are quick and forgiving because they have no hull to remove. They do produce a softer tempeh than soybeans, so the key is to keep them intact and not overcook them.
1. Rinse
Rinse 500 g orange lentils in cold water until the water is clearer.
2. Cook
Cook in plenty of water until just tender but not falling apart. This usually takes 6 to 10 minutes depending on the lentils. Start checking early. You want them cooked through, but still holding shape.
If they become mushy, the tempeh will not bind well. If this happens, you can still ferment it, but it will be more crumbly and better for crumbling than slicing.
3. Drain and Dry the Surface
Drain the lentils very well. Spread them on a tray lined with a clean towel or paper and let them steam off for 15 to 30 minutes. Stir once or twice.
This step is essential. Lentils should feel dry on the outside. They should not look glossy or wet. Moisture trapped in the bag can cause bacterial spoilage and stop the mold from taking over.
4. Acidify
Transfer the lentils to a clean bowl. Add 2 tablespoons vinegar and mix. Acidification helps Rhizopus establish faster and reduces the risk of unwanted microbes.
5. Inoculate
When the lentils are at room temperature, sprinkle the tempeh starter evenly and mix very thoroughly. Starter must be distributed well. Clumps lead to uneven growth.
6. Pack and Add Holes
Pack the inoculated lentils into a bag in a layer about 2 to 3 cm thick. Press it into a flat rectangle.
If you use zip bags, pierce holes every 2 cm on both sides. You need a lot of holes. Tempeh needs oxygen.
7. Incubate
Keep at 28 to 32°C for 24 to 36 hours. Check after 18 to 24 hours for warmth and growth.
A good tempeh will smell fresh, mushroom-like, slightly nutty. It should turn white and hold together when lifted.
If it smells sharp, cheesy, or unpleasant, stop and discard.
Version 2: Mixed Legume Tempeh (More Texture, More Character)
Mixed legumes make beautiful tempeh, especially when you want more bite and a more complex flavor. The key is to pick legumes that cook to a similar firmness.
Good mixes include:
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chickpeas + lentils
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yellow split peas + beans
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soybeans + chickpeas
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black beans + chickpeas
Avoid combining very small and very large legumes unless you cook them separately.
1. Soak
Soak hard legumes (beans, chickpeas) overnight in plenty of water. Lentils and split peas often do not need soaking, but soaking still helps consistency.
2. Cook Until Tender but Firm
Cook each legume type until tender but holding its shape. Drain very well.
3. Remove Skins If Needed
For chickpeas and soybeans, removing skins helps binding and prevents pockets of moisture. You do not need perfection. Even partial dehulling improves results.
4. Dry the Surface
Spread cooked legumes on a tray and let steam escape until surfaces are dry. This can take 30 to 60 minutes depending on the legumes.
5. Acidify and Inoculate
Add vinegar, then starter, mixing thoroughly.
6. Pack Thin and Add Holes
Same as above. Keep the layer no thicker than 3 cm and provide lots of airflow holes.
7. Incubate
Expect 36 to 48 hours depending on the mix and temperature.
How to Do It Without Fancy Machines
You do not need an incubator. You need warmth and a bit of stability. Here are practical options that work well.
Option 1: Oven with the light on
Put the tempeh in the oven with only the light on. Check temperature with a simple thermometer if possible. Many ovens sit around 28 to 32°C with the light.
Option 2: A cooler box
Place the tempeh inside a cooler with a warm bottle of water. Replace the bottle when it cools. This creates a stable warm environment.
Option 3: On top of a fridge or near a boiler
Many kitchens have a naturally warm spot. Use it if it stays above 26°C consistently.
Option 4: Heating pad
A simple seedling mat or low heating pad under a towel works well. Do not let it overheat. Tempeh can cook itself if too hot.
Tempeh produces heat as it grows. If your setup is too warm, the center can overheat and the culture can stall. If you notice the bag becoming very hot, open the door slightly, move it to a cooler spot, or reduce insulation.
When Is Tempeh Ready
Tempeh is ready when:
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it is mostly white and fully bound
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it holds together as a firm cake
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it smells clean and pleasant, like mushrooms and nuts
A few grey spots from spore formation are not dangerous, but they indicate it is getting older. For a mild taste, use it when fully white, before heavy sporulation.
Once ready, store in the fridge up to 5 days, or freeze for longer.
Cooking and Using Tempeh
Fresh tempeh has a mild, nutty flavor and absorbs seasoning exceptionally well. Before cooking, it is often steamed briefly to stabilize the fermentation and remove bitterness.
We explore different preparations, including slicing, crumbling, marinating, and grilling. Tempeh’s strength lies in its structure. It can be pan-fried until crisp, simmered without falling apart, or fermented further.
We also discuss how tempeh behaves differently from tofu or seitan, and why treating it as its own ingredient leads to better results.