Choosing a Koji Starter: General Principles (麹スターターの選び方)
Dried koji and tane-koji spores are sold internationally. This page gives the general principles only - not home long-fermentation procedures.
| Two different products | Ready koji (rice already carrying the mould) for cooking use, and tane-koji spore powder for making koji itself - they are not interchangeable |
|---|---|
| Strain choice | Starters are sold by purpose: for miso, for shoyu, for amazake and general use. Match the stated purpose to your use |
| Sellers named in research | GEM Cultures (US, about 45 years trading) imports Japanese koji starters; Hishiroku spores from Kyoto are listed on Amazon.com |
This guide deliberately stops at principles. Making miso or shoyu at home is a long fermentation, and a neutral reference is not the place for step-by-step instructions: food safety depends on salt ratios, temperatures and handling that must come from the starter maker's own directions and public food-safety guidance.
What can be said generally: buy food-grade starter from a specialist seller, choose the strain by its stated purpose, check the spore count or weight and the best-before date, and store spores cool and dry as the seller directs. Ready-to-cook dried koji - for shio koji, amazake and pickles - is the practical entry point and needs no spore handling at all.
If you do ferment at home, follow one maker's complete directions rather than mixing sources, keep notes of dates and ratios, and when in doubt about a batch, public food-safety guidance in your country is the authority - not this guide.
See also
Books and tools for beginnersRelated page in this guide.What is koji?
Related page in this guide.
Sources: Ministry of Agriculture, Forestry and Fisheries (MAFF), 'Traditional Foods in Japan'; JAS soy sauce standards; Umami Information Center; Kikkoman official information; Wikipedia (CC BY-SA 4.0). Checked 6 November 2026.