Processed
Traditional Usar Leaf Inoculum
A tier
Usar is the Javanese method of growing tempeh mould on hibiscus or related leaves, then using those spore-dusted leaves to inoculate the next batch of beans. It is a living, place-specific starter, not a freeze-dried powder. The cake carries whatever Rhizopus (and fellow travellers) the leaf house has kept, plus a faint green, herbal note some makers prize. It does not ship like a sachet and it does not belong in a HACCP plant without a great deal of work. For a cook in Yogyakarta it is the culture. For everyone else it is a traditional variety to understand, not a supermarket SKU. Hygiene still matters—usar is not an excuse for a slimy incubator.
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History
Javanese tempeh makers transferred mould on hibiscus leaves known as usar.
Usar production remained a household and cottage speciality beside early powdered starters.
Food scientists documented usar microflora while factories moved to pure Rhizopus.
Cultural revival projects taught usar-making to keep the leaf inoculum alive.