A STUDY ON THE RETROGRADATION OF WAXY COR N STARCH

DSC (differential scanning calorimetry) and X-ray diffraction have bee n used for study of retrogradation of waxy corn starch. DSC measurment s were performed in the temperature ranges of -15 degrees C to 15 degr ees C and 30 degrees C to 100 degrees C. For a waxy corn starch soluti on, a sharp endothermic peak was detected at about 0 degrees C immedia tely after gelatinization, and no other endothermic peaks were confirm ed. After the solution was retrograded, a re-gelatinization endothermi c peak was observed, and the endothermic peak at 0 degrees C was separ ated into two peaks. This result and the endothermic peak which is obs erved in the regelatinization process were related to each other, and these are regarded as a result of the retrograda tion. For refrigerate d samples at -18 degrees C, no endothemic peak to be attributed to ret rogradation was detected even after 72 days. X-Ray powder diffraction of the material obtained from the retrograded waxy corn starch solutio n, by precipitating with acetone, indicated that the diffraction patte rns can be attributed to a crystalline B-forms. While, the heat of re- gelatinizetion on the basis of dry starch was approximately constant, this fact suggests that the mechanism of retrogradation may not be inf luenced by the concentration of solution. From these results, we propo se that the waxy corn starch molecular structure can be attributed to gelatinization and retrogradation.