Freeze-Drying, 1949 r.

Freeze-Drying, 1949 r. - Flosdorf Earl W.

Drying, or desiccation, is known to preserve biomaterials, including foods. In freeze-drying, water is evaporated in a frozen state in a vacuum, by means of sublimation (the process of changing a solid to a vapor without first changing it to a liquid). In 1811, John Leslie had first caused freezing by means of the evaporation and sublimation of ice. In 1813, William Wollaston demonstrated this process to the Royal Society of London. It does not seem to have occurred to either Leslie or Wollaston to use sublimation for drying. That distinction goes to Richard Altmann, a German histologist, who dried pieces of frozen tissue in 1890. Later, in 1903, Vansteenberghe freeze-dried the rabies virus. In 1906, Jacques Arsene d’Arsonval removed water at a low temperature for distillation. Since water removal is the essence of drying, d’Arsonval is often credited with the discovery of freeze-drying, but the first clearly recorded use of sublimation for preservation was by Leon Shackell in 1909. His work was widely recognized, and he freeze-dried a variety of biological materials. The first patent for freeze-drying was issued to Henri Tival, a French inventor, in 1927. In 1934, William Elser received patents for a modern freeze-drying apparatus that supplied heat for sublimation. In 1933, Earl W. Flosdorf had freeze-dried human blood serum and plasma for clinical use. The subsequent efforts of Flosdorf led to commercial freeze-drying applications in the United States.