| abstract |
A method of preserving sensitive biological dispersions, suspensions, emulsions and solutions by forming stable foams from fluid materials to be dehydrated, as an aid both to the drying of one or more biologically active substrates in the fluid and as an aid in preparing an easily divisible dried product suitable for further commercial use. The stable foams are formed by partially removing the water to form a viscous liquid and by further subjecting the reduced liquid to vacuum, to cause it to "boil" during further drying at temperatures substantially lower than 100 degrees C. In other words, reduced pressure is applied to viscous solutions or suspensions of biologically active materials to cause the solutions or suspensions to foam during boiling, and during the foaming process further solvent removal causes the ultimate production of a stable open-cell or closed-cell foam. |