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Resumo(s)
The kinetics of thermal degradation of ascorbic acid was studied in a
Maltodextrin matrix at different temperatures between 7.5 and 140°C. Isothermal
experiments were performed with samples earlier equilibrated in environments of
known a, at 4°C enclosed in hermetically sealed vials, with water contents (w)
between 0.17 and 168g water/g solids. Sampling times were selected according
to an optimal experimental design in terms of minimum confidence regions of
the parameters estimated, using the Bigelow model and estimates from
preliminary experiments. The results showed a quadratic dependence of the
reference D-value and linear dependence of the z-value with moisture content:
D r(1400C, = 150*07-290*73w+-269w2 (min); z = 12*14+22.99w (“C) and
showed the applicability of D-optimal designs for determining kinetic
parameters in complex situations, with limited experimental requirements. The
dependence of the rate constants with water content could not be described by
the WLF model in qualitative terms, although in absolute values this model
could be used with constants similar to those expected from glass transition
theory. The thermodynamic analysis of the results showed a good application of
the compensation theory in the whole range of water contents.
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Contexto Educativo
Citação
FRIAS, Jesus M. ; OLIVEIRA, Jorge C. ; CUNHA, Luís M. - Degradation Kinetics of Ascorbic Acid at Low Water Contents. Joumal of Food Engineering. ISSN 0260-87741. Vol. 38 (1998), p. 69-85
Editora
Elsevier