科研之友
微信
新浪微博
Facebook
分享链接
摘要
Enthalpy relaxation experiments were conducted in freeze-dried raspberry powder at 5, 10 and 15 degrees C below its onset glass transition temperature (T(gi)) using differential scanning calorimetry (DSC). The statistical differences in T(gi) for the raspberry powders aged at (T(gi) - 5), (T(gi) - 10), and (T(gi) - 15) from 6 to 96 h were not significant (p > 0.05). The non-exponential behavior of enthalpy relaxation in raspberry powder was fitted with the Kohlrausch-Williams-Watts (KWW) model. The mean relaxation time constant (tau) (1017.4 h) for raspberry powder aged at the temperature (T(gi) - 15) was greater than the tau (147.1 h) at (T(gi) - 5). The KWW model parameter beta values for freeze-dried raspberry powders were greater than the beta values of pure food constituents. The activation energy for enthalpy relaxation in the glassy state was determined as 145.4 kJ/mol by approximating with the Arrhenius equation. The dependence of mean relaxation time on temperature followed an Arrhenius behavior indicating raspberry powder is a strong system. Several approaches were used to classify raspberry powder into strong/fragile system. There is a difference among fragility parameters of raspberry powders determined using selected methods.
- 出版日期2010-11
