Cotyledon cell walls of navy beans impose restrictions on swelling and gelatinization of bean starch during cooking. The incomplete gelatinization of starch granules ultimately reduces the rate and extent of starch hydrolysis measured as glucose release during 120 min of in vitro digestion with simulated gastric and small intestinal fluids. The stability of cotyledon cells and the small surface area of the starch granules which are tightly packed inside the cells also appear to restrict the free access of amylolytic enzymes during in vitro digestion. Experiments with stored and reheated beans suggest that the extent of gelatinization and availability of water during cooking could be a major factor influencing starch hydrolysis during in vitro digestion.