Sub-Tg annealing of granular rice starch: effects on enthalpy relaxation and starch-sucrose interactions
✍ Scribed by Chee Choon Seow; Chanderan K. Vasanti-Nair
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 689 KB
- Volume
- 261
- Category
- Article
- ISSN
- 0008-6215
No coin nor oath required. For personal study only.
✦ Synopsis
Annealing
of native rice starch at a temperature somewhat below its effective glass transition temperature CT'> increased both the gelatinization onset temperature (7") and enthalpy (AH,) to their respective quasi-equilibrium values, due probably to free volume and enthalpy relaxation, but had little or no effect on crystallite melting temperature (T,). "Maximum" AH, was attained well before "maximum" T', suggesting that excess volume can continue to be dissipated or redistributed without any substantial change in internal energy. The effect of sucrose on AH, appeared to be dependent on the physical condition of the glassy regions of the starch granules, a significant increase in AH, being observed only when sucrose was added to unannealed granular starch with apparently less stable amorphous regions. Addition of sucrose to annealed starch, which possessed lower energy glassy states, yielded no significant changes in AH,. On the other hand, elevation of both To and T, was obtained on addition of sucrose to either physically aged or unannealed starch.