The Complete Handbook of Tempeh

Chapter 1: Understanding Tempeh

Tempeh is a compact, sliceable cake made by controlled fungal fermentation of dehulled, cooked soybeans. Unlike tofu, which is a curd of soy milk, or miso and soy sauce, which are brine or paste ferments, tempeh is a whole-bean product in which the beans are bound together by a network of white mycelium into a solid block. That network is not decorative. It is the structure that lets you slice tempeh thin for frying, grate it into crumbles, or grill it whole without it falling apart. For a cook, the practical difference is in how it behaves in the pan: tempeh holds its shape through high heat and has a firm, chewy texture that is often described as nutty or meaty. For a producer, that texture is the result of a specific biological process that must be controlled within relatively narrow parameters.

The organism responsible for tempeh fermentation is a filamentous fungus from the genus Rhizopus, most commonly Rhizopus oligosporus or Rhizopus oryzae, depending on the strain and the tradition. These fungi produce thread-like cells called hyphae that grow through and around the soybean mass, eventually forming a dense mat of interconnected tissue called mycelium. Under correctly managed conditions, the mycelium binds the beans into a cohesive cake in 24 to 48 hours, depending on temperature, inoculum level, and the characteristics of the substrate batch. This is not a spontaneous fermentation. It requires deliberate steps: cleaning and dehulling, cooking or steeping, acidification to inhibit competitor bacteria,