STARCH FLAVOR - CAN RATS TASTE AN INSOLUBLE SUBSTANCE

Rats given a choice between fluid containing 0.5% starch and the same fluid without starch, consistently prefer the fluid containing starch. The present studies examined whether impurities present in corn starch contribute to this behavior. Corn starch was hydrolyzed to glucose plus impurities by treatment with the enzyme amyloglucosidase. Rats showed little or no preference for fluids containing hydrolyzed starch compared to comparable concentrations of reagent grade glucose. Additional starch samples were treated to remove off-tastes noted by humans. Rats consistently preferred fluids containing 'clean-flavored' starch over fluid without starch. However, a conditioned flavor aversion experiment showed that rats could be trained to discriminate between hydrolyzed starch and pure glucose. The aversion to hydrolyzed starch generalized to unhydrolyzed corn starch but not to starch that had been processed to remove the off-taste detected by humans. Thus, the present experiments suggest that starch flavor has two components. The off-taste component of com starch has little or no effect on preference and is due to impurities. The other, apparently more important, component of starch flavor is attributable to starch itself and is responsible for the preference rats spontaneously show for starch. Starch might therefore be a member of a novel class of chemosensory stimuli, substances that are insoluble in both water and lipids as well as being non-volatile.