Tempeh

Tempeh (Codex spelling tempe) is a bean cake held together by mold, not a paste and not a brine. Mukherjee et al., quoting Codex CXS 313R-2013: a compact, white, cake-form product prepared from dehulled boiled soybeans through solid-state fermentation with Rhizopus spp. Essential composition: soybeans and a mold of R. oligosporus, R. oryzae, and/or R. stolonifer mixed with cooked rice powder, rice bran powder, and/or wheat bran powder as inoculum. No additives. Texture: compact and not easily disintegrated when cut with a knife ¹.

That identity determines the texture. The mycelium is the structure. Slice it and the cake should hold; crumble is a quality failure of incomplete colonization, not a style.

Not koji, not natto #

Koji is Aspergillus oryzae on cooked grain or soy, grown for enzymes that later work in Miso or sauce. Tempeh is Rhizopus on beans, grown until the beans are the food. Same kingdom, different genus and different product.

UMN Extension’s alkali fermentation category is for protein-rich foods such as natto, where bacteria produce ammonia and the product stays low-acid ². Tempeh is not that process. Do not copy natto or kraut clocks onto this cake.

What to notice #

Codex’s sensory claim, via Mukherjee: white luxurious mycelium; compact cut. A clean mushroom-bean smell is the expected direction. Ammonia that dominates, sliminess, or colors that are not the culture you bought are discard cues; there is no reliable rescue for a contaminated cake. Gray or black sporulation at air holes is often discussed in craft literature as ripeness; without an extension home formula, treat unexpected color as a reason to stop, not as a recipe step.

The mold’s Enzymes digest bean protein and change texture from loose beans to a sliceable cake. That is solid-state Fermentation, not lactic souring. pH is not the Codex identity test.

Starter is a safety control #

Allwood, on mold cultures generally: a 2012 outbreak linked a fungal tempeh starter to Salmonella Paratyphi. Use uncontaminated commercial inoculum; do not treat leftover cake as a certified starter ³. Hygiene around soaked beans still matters. NCHFP does not publish a tested home-canning process for tempeh.

Process limits #

Incubation temperature, bag perforation, and time must come from a validated tempeh process; canning is a separate question. Tempeh is outside USDA home-canning tables. See Food safety. The soybean remains within Codex’s product definition.