Lactose relaxation behavior

Kett et al. [1.162] studied Tg in freeze-dried formulations containing sucrose as a function of relative humidity and temperature during storage by TMDSC and ther-mogravimetric analysis. Craig et al. [1.163] found it helpful to asses the relaxation behavior of freeze-dried amorphous lactose by MTDSC. Relaxation times were calculated from measurements of Tg, and the magnitude of the relaxation endotherm. Scannnig was performed at 2°C/min with a modulation amplitude of 0.3 °C and a period of 60 s. 

Craig et al. [1.176] assessed the behavior of amorphous lactose by MTDSC. The relaxation time of 10% freeze-dried amorphous lactose as a function of the difference between annealing (storage) temperature and is given in Figure 1.48.4 The relaxation time 15 K below is 10 h and 35 K below it is -250 h. The authors dis-... 

Another very interesting behavior is observed when comparing loss spectra of both studied herein carbohydrates in the range below Tg (see Fig. 3). There are two, well separated, secondary relaxation processes in lactose. In octa-O-acetyl-lactose only one is detected. A maximum of the secondary relaxation of octa-O-acetyl-lactose is almost the same as that of the y- relaxation of lactose at the chosen temperature. This can suggest that the considered secondary modes in lactose and its acetyl derivative may be of the same origin. Thus, in the further part of this paper we will label the secondary relaxation as a y- processes (just as in the case of lactose). 

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