Storing Fermented Foods and Reading Dates (保存と賞味の読み方)
Japanese date marks, what darkening means in miso, when shoyu fades - the storage facts that apply across this whole guide.
| Two date marks | Shohi kigen (use-by, for perishables) and shomi kigen (best-before, for quality). Most miso and shoyu carry best-before dates |
|---|---|
| Miso darkening | Colour deepens with age and warmth after opening - normal maturation, not spoilage by itself |
| Shoyu after opening | Flavour and aroma fade by oxidation; refrigeration after opening is the maker's usual instruction and keeps the aroma longest |
Fermented seasonings are stable foods, but 'stable' is not 'immortal', and each product's label outranks any general guide - including this one. The general pattern: unopened miso and shoyu keep for months in a cool dark place; after opening, the refrigerator is the default for miso and pickles, and the maker's instruction on the bottle governs shoyu.
Trust senses in order: an off smell that was never there (sharp, solvent-like), visible mould growth spreading inside a paste, or a swollen container are discard signals for any of these foods. Surface colour change alone - miso darkening, a white film of yeast on a pickle bed that a maker's directions describe as normal - is judged by the maker's own guidance, which is the authority this page keeps pointing back to.
See also
Storing after openingRelated page in this guide.Reading a miso label
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.