Sake that is spoiled can have bitter tastes or unpleasant aromas. There are three basic things that damage or spoil sake:
1. Temperature – keep sake stored in a cool location, preferably refrigerated
2. Light – protect sake from direct sunlight and artificial light
3. Oxygen – to a lesser extent than wine, oxidation degrades sake, but much more slowly than wine.
Generally, an unopened bottle of sake should be drunk as soon as possible in order to drink the sake as intended by the toji. However, since transportation and storage through the distribution system can take a number of months, note that sake is best drunk within 12-18 months after the bottling date.
Once opened, keep the sake refrigerated and we recommend drinking within one week, but it also depends on the product. Some sake tastes great after weeks or months in the refrigerator.
Sake should be stored upright, as opposed to flat as with wine.