Although starch is the world's most abundant nutritive carbohydrate, its sensory properties are not as well understood as those of sugars. Previous researchers have assumed that all starches have the same flavor. The present experiments examined flavor differences among starches. Untrained rats were offered a choice of suspensions containing raw versus cooked starch. For some starches (potato and rice), rats strongly preferred cooked over uncooked starch. For other starches (regular corn, corn amylopectin, and wheat), rats showed little or no preference for cooked over uncooked starch. In order to determine whether the greater preference for cooked starch reflects a difference in flavor intensity, rats were conditioned to avoid potato or corn amylopectin starches by pairing ingestion of these substances with lithium chloride injections. Rats trained to avoid raw starch also avoided cooked starch, indicating that cooked and raw starch have similar flavors. However, when these trained rats were offered a choice between cooked and raw starch, they avoided the raw starch; this result is inconsistent with the assumption that cooking enhances the intensity of starch flavor. Similar results were obtained with corn amylopectin and potato starch, even though these starches differ greatly with regard to the effects of cooking on preference in untrained rats. However, rats trained to avoid potato starch avoided this starch to a greater degree than did rats trained to avoid corn amylopectin; conversely, rats trained to avoid corn amylopectin avoided this starch to a greater degree than did rats trained to avoid potato starch. Therefore, the flavor of starch is complex; there are specific flavor notes related to species and cooking.(ABSTRACT TRUNCATED AT 250 WORDS)