What is Tempeh and How is It Made?
Tempeh is an Indonesian food product made from fermented whole soybeans. While the term 'processed' can be misleading, the process for creating tempeh is a natural and beneficial form of food processing known as fermentation. The steps are relatively simple and have been used for centuries.
The Simple Steps to Making Tempeh:
- Soaking: Dried soybeans are soaked in water for an extended period, which softens them and begins a mild lactic acid fermentation.
- De-hulling: The outer skins of the soybeans are removed, a process that helps the mold grow more effectively.
- Cooking: The de-hulled soybeans are cooked until they are soft but not mushy, ensuring there is enough air circulation between the beans.
- Inoculation: A starter culture, typically a Rhizopus mold, is mixed into the cooled beans along with a small amount of vinegar.
- Incubation: The beans are packed into a flat, porous form and incubated at a warm, constant temperature for 24 to 48 hours. During this time, the mold grows, binding the beans into a firm, solid block.
Minimally Processed vs. Ultra-Processed
The distinction between different levels of food processing is crucial. Minimally processed foods, like tempeh, undergo simple alterations that don't fundamentally change their nutritional content. This can include fermentation, freezing, or pasteurization, all of which are done to improve preservation or safety without adding unhealthy fats, sugars, or artificial ingredients. Ultra-processed foods, by contrast, are typically made with many added ingredients like flavorings, colors, and preservatives, and often have a high calorie-to-nutrient ratio. A key reason tempeh is not ultra-processed is that the final product is essentially the whole soybean, transformed and bound by beneficial mold, with minimal added ingredients.
Tempeh's Nutritional Edge from Minimal Processing
Tempeh's gentle fermentation process offers distinct nutritional benefits that more intensive processing methods often strip away. Fermentation breaks down complex nutrients into simpler, more digestible forms, making tempeh easier for the body to absorb. It also reduces compounds known as anti-nutrients, such as phytates, which can otherwise inhibit mineral absorption. The result is a highly bioavailable source of protein, fiber, and minerals.
Tempeh vs. Tofu vs. Ultra-Processed Alternatives
To truly understand tempeh's processing level, it's helpful to compare it to other popular plant-based proteins.
| Feature | Tempeh | Tofu | Ultra-Processed Alternative (e.g., 'Vegan Bacon') |
|---|---|---|---|
| Raw Material | Whole, cooked soybeans | Soy milk (extracted from soybeans) | Highly refined and isolated proteins/starches |
| Processing | Soaking, de-hulling, fermentation, packaging | Soaking, grinding, boiling, filtering (to make milk), coagulating, pressing | Industrial extrusion, multi-stage refining, high-heat processing |
| Core Ingredients | Whole soybeans, starter culture | Soybeans, water, coagulant (e.g., calcium sulfate) | Isolate proteins, oils, sugars, yeast extract, artificial flavorings, colorings, stabilizers |
| Resulting Product | A dense, fibrous, cake-like block with a nutty, earthy flavor | A soft or firm custard-like block with a neutral flavor | A highly-engineered product that mimics animal meat in taste and texture |
| Nutritional Profile | High in protein and prebiotic fiber; nutrient bioavailability enhanced by fermentation. | Good source of protein and calcium, but lower in fiber than tempeh because of processing. | Can be high in sodium, fat, and calories with added fillers; minimal nutritional benefits beyond basic protein content. |
| Health Classification | Minimally Processed Whole Food. | Processed Food. | Ultra-Processed Food. |
Understanding the Fermentation Benefits
The use of a beneficial mold in tempeh production is central to its nutritional profile. The mold's mycelium not only binds the whole beans together but also initiates changes that improve tempeh's health benefits. While pasteurization, a common final step for commercial products, inactivates live probiotics, the process still leaves behind the prebiotic fiber that feeds good gut bacteria. Additionally, the fermenting mold breaks down complex carbohydrates, which can make tempeh easier to digest for some people compared to unfermented soy products.
Conclusion
In summary, the notion that tempeh is overly processed is a misconception rooted in a general distrust of processed foods. In reality, the processing tempeh undergoes is a simple, beneficial, and centuries-old fermentation practice. Unlike ultra-processed meat alternatives or even its soy cousin, tofu, tempeh is a whole food that retains the nutritional benefits of the entire soybean, including high fiber and protein content. The fermentation process enhances its digestibility and unlocks key nutrients, making tempeh a highly nutritious and minimally processed choice for anyone looking to incorporate more plant-based protein into their diet. For a deeper understanding of food processing classifications, the Harvard T.H. Chan School of Public Health offers valuable insights on Processed Foods and Health.
