Publication no. C-2000-0412-02R |  VIEW ARTICLE

Relationship of Gelatinization and Recrystallization of Cross-Linked Rice to Glass Transition Temperature.

Pathama Chatakanonda (1), Saiyavit Varavinit (1,2) and Pavinee Chinachoti (1,3). (1) Food Science Department, University of Massachusett, Amherst, MA 01003. (2) Current address: Department of Biotechnology, Mahidol University, Rama Rd., Bangkok, 10400 Thailand. (3) Corresponding author. E-mail: <pavinee@foodsci.umass.edu> Phone: 413/545-1025. Fax: 413/545-1262. Cereal Chem. 77(3):315-319. Accepted January 18, 2000. Copyright 2000 American Association of Cereal Chemists, Inc.

Nonwaxy rice starch was cross-linked with sodium trimetaphosphate and sodium tripolyphosphate to obtain different degrees of cross-linking (9.2, 26.2, and 29.2%). The objective was to investigate the influence of cross-linking on thermal transitions of rice starch. Starch suspensions (67% moisture) were heated at 2°C/min using differential scanning calorimetry (DSC) to follow melting transition of amylopectin. Biphasic transitions were observed at approximately 60-95°C in all samples. Melting endotherms of amylopectin shifted to a higher temperature (<=5°C) with an increasing degree of cross-linking, while there was no dramatic change in enthalpy. Recrystallization during aging for 0-15 days was significantly suppressed by cross-linking. The delayed gelatinization and retrogradation in cross-linked starch were evident due to restricted swelling and reduced hydration in starch granules. Glass transition temperature (T(g)) measured from the derivative curve of heat flow was -3 to -4°C. No significant change in T(g) was observed over the storage time studied.