Dried beans are a traditional staple in many cultures, prized for their high-quality protein and almost limitless shelf life. While meat requires a great deal of effort to preserve safely, beans require nothing more than a bit of sun and dry air. The USAID fact sheet on pinto beans says that, like other dried beans, they will "keep indefinitely if stored in a dry place." Although the beans will remain edible for an extended period, they may suffer some deterioration in texture or flavor. Look for clear warnings signs to tell whether your beans are stale or too old.
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Examine the pintos closely for signs of mold and moisture. Dried foods are safe because they do not contain enough free water for microorganisms to survive in them. Pinto beans are normally a pale-tan color. If they have dark blotches or mottled skin, or if there is any visible trace of mold on them, they should be discarded.
Smell the beans, searching for any off odors. Well-kept pintos will have only a mild aroma of the beans themselves. Off smells might indicate molding, damage or droppings from pests, fermentation or simply absorption of unpleasant odors from the storage area. If the beans have a strong smell, they should be discarded.
Examine the pintos and their packaging for any signs of insect or rodent damage. If the packaging shows signs of being chewed through, if live or dead insects are found in the beans or if there are any beans that appear to have been chewed, the entire container of beans should be discarded.
Cook a test batch of beans, if none of the previous tests reveal any obvious problems. Dried pintos are best within one year of harvest and will take longer to cook as they get older. Simmer the beans until tender, making a note of the time required. You will need that information for your next batch.
Taste the beans to ensure that their texture and flavor are adequate. If they pass the taste test, the pintos can be used as appropriate in your favorite recipe.