Albumin residual moisture content

Greiff [3.24] studied the stability of purified influenza virus of the strain PR 8 in physiological NaCl solution with calcium lactobionate and human serum albumin (each 1 % in the solution). The freezing rate was approx. 1 °C/min down to -30 °C. During the freeze drying, the product temperature was raised in 12 to 16 h from -30 °C to 0 °C and the product was dried at this temperature. After 24 h, the first 145 vials were removed, and additional vials after intervals of 24 h each. The residual moisture content was 3.0,2.0,1.5, 1.0 and 0.5 %. The stability of the freeze dried virus (expressed in days during which the titer of the infectivity decreased by a factor of 10 was most unfavorable at 0.4 % and 3.2 % RM, (4 and 7 days respectively at +10 °C) and best at 1.7 % RM 145 days or more than 1000 days at -10 °C. 

Fig. 2.93. Residual moisture content (dW) as a function of time. 100 vials with 10% albumin solution, with different pc, different freezing methods and layer thickness as parameter.

Virtually all the proteins in animal blood can be dispersed into useful adhesive form. These include the serum albumin and globulin and even the red cell hemoglobin [42]. The fibrin clotting substance is sometimes removed before drying (by agitation or acidification) because of its instability in solution. Thus, except for residual moisture content, dried blood is essentially 100% active adhesive protein. 

Pikal and Shah [43] studied intravial distribution of residual moisture in dextran, human serum albumin, and bovine somatotropin. In general, the residual moisture in the top of a core sample of the freeze-dried product was less than the moisture content in the bottom core section of the product. The section closest to the vial wall was consistently found to be lowest in moisture content. 

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