Once opened, Cornstarch keeps about 18 months in the pantry. Unopened, it keeps about 18–24 months.
18 months opened in the pantry, against 18–24 months sealed in the pantry. Green is what this situation leaves you; husk is what it spends.
| Situation | Keeps for |
|---|---|
| Unopened · pantry | 18–24 months |
| Opened · pantry | 18 months |
Air and warmth are what shorten an opened item's life — the right container buys back the days the packaging gives up once the seal's broken.
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About 18 months in the pantry, according to USDA FoodKeeper v128.
Cornstarch is shelf-stable at room temperature: cool, dry pantry, sealed — refrigerating after opening is optional and mainly preserves quality. Refrigerating it mainly preserves quality rather than safety.
Look for: A rancid, paint-like, or musty smell; Clumping, or moisture in something that should be dry; Insects, webbing, or larvae in the package; Faded colour or a lost aroma. Those are the general signs for baking & cooking — USDA FoodKeeper v128 publishes no spoilage note for Cornstarch specifically. Never taste something to test it — when in doubt, throw it out.