| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 708.99 KB | Adobe PDF |
Autores
Orientador(es)
Resumo(s)
This work describes a method to study glass transition on native starch powders, based
on dynamical mechanical thermal analysis using compression tests, and was applied to
wheat flour (13.5% water content). This method will allow the determination of Tg in
native (unprocessed) starchy materials, with minimal disturbance of the natural structures.
The influence of the test conditions (heating rate, frequency and strain) on the glass
transition measurements was determined using factorial designs. The values of Tg determined
as the maxima of the energy dissipation (peaks in E ) of native flour and of freezedried
pre-gelatinized flour were not statistically different (around 64 C). The heating rate
did not affect the measurements in the range tested (0.25 to 1 C min 1). An interactive
effect of the strain amplitude and the frequency was detected. The significance of this
interaction can be caused by differences in mechanical energy dissipation, which would
indicate that not only temperature but also the total energy input may affect this transition.
Slight effects of phase separation between gluten and starch were found on native
flour.
Descrição
Palavras-chave
Phase transitions Starch Viscoelastic properties
Contexto Educativo
Citação
PEREIRA, Pedro M.; OLIVEIRA, Jorge C. - Wheat flour by dynamic mechanical thermal analysis (DMTA). International Journal of Food Science and Technology. ISSN 0950-5423. Vol. 35 (2000), p. 183–192
Editora
Wiley Blackwell Science Ltd