It is soup season and many recipes include dried beans. But how can you tell if they are old? One specific sign dried beans are old, is if they wrinkle during soaking.
As dry beans soak, they should absorb moisture through the hilum, the part of the bean that attaches to the pod. But during harvest handling and storage, dry beans can develop holes, called “checks”, due of temperature changes, moisture changes, and fungi growth. The “checks” allow water into the bean and wrinkle the skin.
Since these “checks” are difficult to see before cooking, always buy new beans and use remaining dry beans within one year.
Source: The Science of Good Cooking, Cook’s Illustrated