When baked goods go stale, why does bread turn hard, while crackers soften?
According to our science editor, crackers are manufactured to be very dry to make them shelf-stable. Once the package is opened and the crackers are exposed to air, their sugars and starches start to absorb ambient moisture. After a few days, the once-crisp crackers will be soft and soggy.
When bread turns stale, an entirely different process takes place. Once exposed to air, bread starch undergoes a process called retrogradation: The starch molecules in the bread begin to crystallize and absorb moisture, turning the bread hard and crumbly.