Abstract
It has been known that white potato is hard to cook soft when heat is turned off for a while when potato is halfdone. The authors made a study on this problem in terms of gelatinization and retrogradation of starch. The degree of gelatinization of starch was estimated by the methods of using glucoamylase and of X-ray diffraction. The starch of chipped potato (5mm cubic) was not gelatinized completely by heating below 70°C for 60min. but it was gelatinized fully at 100 °C for 10min. When heating was stopped before the complete gelatinization of the starch of the chipped potato and it was cooled below 40°C (e.g. at 20°C for 1 hour), the starch could not be gelatinized fully by reheating at 100°C for 10min. or more. The starch of the partially cooked potato chips showed the more rapid retrogradation than of the well cooked ones. These results indicate that the change made by the arresting of heat in the halfway process of cooking is related mainly to the gelatinization and retrogradation of starch.
