Glass transitions and state diagram for freeze-dried pineapple
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Data
2001-01-01
Autores
Telis, VRN
Sobral, PJA
Título da Revista
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Título de Volume
Editor
Elsevier B.V.
Resumo
Glass transition temperature of freeze-dried pineapple conditioned by adsorption at various water activities at 25 degreesC was determined by differential scanning calorimetry (DSC). High moisture content samples corresponding to water activities higher than 0.9, obtained by liquid water addition, were also analysed. The DSC traces showed a well-visible shift in baseline at the glass transition temperature (T(g)). Besides, no ice formation was observed until water activity was equal to 0.75. For water activities lower than 0.88, the glass transition curve showed that T(g) decreased with increasing moisture content and the experimental data could be well-correlated by the Gordon-Taylor equation. For higher water activities, this curve exhibited a discontinuity, with suddenly increasing glass transition temperatures approaching a constant value that corresponds to the T(g) of the maximally freeze-concentrated amorphous matrix. The unfreezable water content was determined through melting enthalpy dependence on the sample moisture content.
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Palavras-chave
pineapple, glass transition, DSC, water activity
Como citar
Lebensmittel-wissenschaft Und-technologie-food Science and Technology. San Diego: Academic Press Inc. Elsevier B.V., v. 34, n. 4, p. 199-205, 2001.