Temperature effect on retrogradation rate and crystalline structure of amylose

Commercial potato amylose was used to study temperature effects on the retrogradation of amylose solutions (3.5mg/ml). The retrogradation rate decreased as incubation temperature increased (5 to 45¢XC). The degree of retrogradation within 24h decreased from 58.8 to 7.1% as incubation temperature increased from 5 to 45¢XC. In the amylose solution, different-sized molecular subfractions retrograded at different rates. After incubating at 5¢XC for 100 days, the majority of the amylose molecules retrograded and precipitated from the solution; at 45¢XC, only amylose of the small-molecular subfraction (number average, DPn = 110; weight average, DPw = 150) retrograded and precipitated. Entanglement of molecules was observed in size exclusion chromatograms. The morphology of retrograded amylose observed by using a scanning electron microscope differed with the retrogradation temperature. The chain length of amylose crystalline segments, prepared by hydrolysis of retrograded amylose, showed a narrow distribution (polydispersity from 1.21 to 1.67). The chain lengths of resistant segments increased DPn from 39 to 52 and DPw from 47 to 72 for £\-amylolysis and DPn from 34 to 40 and DPw from 48 to 67 for 16% sulfuric acid hydrolysis, when incubation temperature increased from 5 to 45¢XC. ? 1997 Elsevier Science Ltd.