P. Chatakanonda et al., Relationship of gelatinization and recrystallization of cross-linked rice to glass transition temperature, CEREAL CHEM, 77(3), 2000, pp. 315-319
Nonwaxy rice starch was cross-linked with sodium trimetaphosphate and sodiu
m tripolyphosphate to obtain different degrees of cross-linking (9.2, 26.2,
and 29.2%). The objective was to investigate the influence of cross-linkin
g on thermal transitions of rice starch. Starch suspensions (67% moisture)
were heated at 2 degrees C/min using differential scanning calorimetry (DSC
) to follow melting transition of amylopectin. Biphasic transitions were ob
served at approximate to 60-95 degrees C in all samples. Melting endotherms
of amylopectin shifted to a higher temperature (less than or equal to 5 de
grees C) with an increasing degree of cross-linking, while there was no dra
matic change in enthalpy. Recrystallization during aging for 0-15 days was
significantly suppressed by cross-linking. The delayed gelatinization and r
etrogradation in crosslinked 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 degrees C.
No significant change in T-g was observed over the storage time studied.