Opened a bottle of junmai about three weeks ago, kept it in the cupboard with the cap back on, and had a glass tonight. It is sharp and sour in a way it absolutely was not on the first night. Vinegar is the closest description.
The bottle was not cheap and I would like to know whether I ruined it or bought it ruined. Is three weeks open a long time for sake?
Worth adding that most everyday sake is not meant to be kept. Aged styles exist, but a standard bottle does not improve on a shelf for a year, and people treat it like wine and are then disappointed.
What good sake should taste like, for comparison: fruity and floral, or rich and ricey, or dry and crisp, or savoury. Some styles are noticeably acidic, but balanced and fresh rather than sharp and souring.
Pour it away if it smells sharply of vinegar or has gone cloudy when it was not a cloudy style to begin with.
For anybody here who brews rather than buys, the homemade version of this has the same culprit from a different direction. Acetic acid bacteria get in, usually through oxygen exposure plus warm temperatures, and turn the alcohol to acid.
So sanitation genuinely matters, keep the ferment cool, and limit air contact once the active fermentation slows rather than leaving a half-empty vessel open to the room. If a homemade batch smells strongly of vinegar it is usually a start-again rather than a rescue.
@namazake_fridge · 2w ago · 3 replies
You ruined it, gently, and the cupboard did most of the work. Once a bottle is open the sake is in contact with oxygen and starts changing: over days to weeks it loses aroma and goes flat, then sour and stale. Three weeks is well past it.
Heat and light accelerate all of that, so a cupboard is worse than a fridge and a sunny shelf is worse again. Opened sake goes in the fridge, resealed, and most sources suggest drinking it inside a week or two for the flavour you paid for.
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@open_two_weeks · 2w ago
Does that apply to unopened bottles too, or can those sit in a cupboard happily?
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@namazake_fridge · 2w ago
Unopened is fine somewhere cool and dark, upright and out of the light, with one exception. Namazake is unpasteurised and is more delicate: that lives in the fridge from the day you buy it and spoils more readily if it is kept warm. Check the label for it.
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