Fresh beans show signs of spoilage readily -- brown dots or stripes, discoloration and fading, white or grey fungus and a musty odor indicate fresh beans are past their prime. Cooked, canned and dry beans require more observation to determine freshness, but their spoilage indicators are as apparent as those of fresh beans when you know what to look for.
The U.S. Department of Agriculture considers wrinkly skins, breaks or chips, blisters and holes -- commonly caused by weevils -- signs of unsound dried beans.
Storage conditions influence shelf life of dry beans dramatically. Dry beans stored in airtight mylar bags last 30 years or more. Dry beans stored in their commercial packaging start losing quality after one year. However, dry beans past their shelf life aren't necessarily harbingers of foodborne illness, but merely take longer to cook due to reduced moisture content and have diminished vitamin content as compared to dry beans within their shelf life.
Determining spoilage in canned beans is difficult until you open the can, and even then, some toxins can go unnoticed -- botulism spores, for example, have no odor or color. For canned beans, both home-processed and store-bought, can damage is the first indication of a spoiled product.
Dents, bulging lids, corrosion and spurting liquid or the sound of gas escaping upon opening means the beans have been compromised and should be thrown out. Upon opening, signs of spoilage include a sour odor and a white viscous fluid surrounding the beans.
A sour smell, surface bubbling and a mucus-like film on the surface of the food and around the beans are common signs of spoiled bean dishes. If the dish contains other highly perishable ingredients, such as meat, those ingredients typically turn before the beans do. In those cases, use the item in the dish that has the shortest shelf life to determine shelf life of the overall dish.
- Store dry beans in the freezer to extend their shelf life indefinitely.
- Store cooked beans in an airtight container in the refrigerator for a shelf life of four to five days.
- Store canned beans in the pantry for as long as one year after purchase.