VII. QUICK-FREEZING AND FREEZING-DRYING 229 



There would have been little justification for starting without the 

 assurance tliat at the end they would still be dealing with an organism 

 of unchanged characteristics. Freeze-drying made this possible. 

 As a result of this work carried on by Siler and associates, a far better 

 vaccine for preventing typhoid fever was produced and was available 

 for use in World War II. This is another major, although indirect, 

 contribution that freeze-dr3dng made to the great success of American 

 military medicine during the w^ar. Welch, Borman, and Mickle re- 

 ported successful application to Klebsiella pneumoniae in unaltered 

 form (30). 



Flosdorf and Kimball reported on extensive use of freeze-drying 

 with Hemophilus pertussis (6). In this case, agglutinin absorption 

 w^as used to demonstrate that no dissociation occurs as a result of 

 drying. The fundamental importance in antibacterial immunity of 

 the combination of agglutinins with surface antigens of bacteria is 

 well established. With nonflagellated organisms the use of such sur- 

 face reactions as agglutination or phagocytosis therefore provides dis- 

 tinguishing methods of assay for effective surface reactants in either 

 serum or antigen. Complement fixation and precipitin testing with 

 soluble antigens are of diagnostic value but do not distinguish sur- 

 face antigen-antibody combination from phenomena involving other 

 antigens. 



Appleman and Sears (31) reported that legume nodule bacteria 

 {Rhizohium leguminosarum) retain viability and their ability to nodu- 

 late plant hosts and to fix nitrogen after four years of storage without 

 loss. Bacteria tested w^ere isolated originally from alfalfa, lespedeza, 

 cowpea, pea, soybean, vetch, crown vetch, and clover host plants. 

 The cultures were gro^vn on asparagus mannitol medium and then 

 emulsified in sterile water for drying. 



Freeze-dried viable cultures of molds and bacteria are now avail- 

 able commercially in the dairy industry as "starters" for first propaga- 

 tion in production of cottage cheese, buttermilk, butter acidophilus, 

 Bulgarian milk, and yoghurt. 



3. Preservation of Miscellaneous Products 



As has been discussed earlier in this chapter, blood plasma was 

 preserved on a very large scale during World War II. It represented 

 the largest application of freeze-drying until that time. Plants were 

 erected throughout the country for the purpose. The method was 

 also employed as part of the fractionating procedure in the Cohn 



