^ âeucatastropheâ (US) / âeucatastropheâ (UK) in Oxford Dictionaries, Oxford University Press.
A: Chopped or sliced onions can be stored in a sealed container in your refrigerator at the proper temperature of 40Â°F or below for 7 to 10 days (Source: USDA). For pre-cut fresh or frozen products, always use and follow manufactures use by dates.
After being cut, onions can be stored in the refrigerator in a sealed container for up to 7 days. A widely circulated claim states uncooked, leftover onions are 'poisonous' because they're 'a huge magnet for bacteria,' thus likely to spoilage.