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 ra te decreased as incubation temperature increased (5 to 45 degrees C). The degree of retrogradation within 24 h decreased from 58.8 to 7.1% a s incubation temperature increased from 5 to 45 degrees C. In the amyl ose solution, different-sized molecular subfractions retrograded at di fferent rates. After incubating at 5 degrees C for 100 days, the major ity of the amylose molecules retrograded and precipitated from the sol ution; at 45 degrees C, only amylose of the small-molecular subfractio n (number average, DPn = 110; weight average, DPw = 150) retrograded a nd precipitated. Entanglement of molecules was observed in size exclus ion chromatograms. The morphology of retrograded amylose observed by u sing a scanning electron microscope differed with the retrogradation t emperature. The chain length of amylose crystalline segments, prepared by hydrolysis of retrograded amylose, showed a narrow distribution (p olydispersity from 1.21 to 1.67). The chain lengths of resistant segme nts increased DPn from 39 to 52 and DPw from 47 to 72 for alpha-amylol ysis and DPn from 34 to 30 and DPw from 48 to 67 for 16% sulfuric acid hydrolysis, when incubation temperature increased from 5 to 45 degree s C. (C) 1997 Elsevier Science Ltd.