Freeze-drying has been correctly defined ‘as a process in which food, once frozen, is introduced into a vacuum chamber that separates the water by sublimation. Through different cycles of freezing-evaporating, it manages to eliminate virtually all the free water contained in the original product.’
The process of freeze-drying products – mainly in the food industry – begins once the raw material is harvested, prepared and immediately frozen, then passed into the freeze-drying process in a vacuum chamber. During this process, and under the influence of a slight warming, the water contained in the product in the form of ice is converted into steam and eliminated from the cells. The shape, colour, size, and consistency is preserved. The porous structure of the resulting cells in the final product allows for quick absorption of water when rehydrated.
The freeze-drying process retains the maximum flavour, vitamins, minerals, and aromas of the original product. Freeze-drying produces a completely natural product free from additives and preservatives.
An ancestral and, of course, very basic antecedent to freeze-drying arose out of necessity and a favorable environmental climate. For centuries it was used by the Incas and Vikings, who required high-calorie, lightweight food, that was easy to transport (low weight and volume) and did not rot, for their long journeys and military incursions.
The Incas took advantage of the high Andes with their icy nights and daytime sunlight to transform potatoes (papas) into chuño (made with potato starch) and llama meat into charqui (dried meat), carrying them in their backpacks – possibly the first products in history to be freeze-dried in a rustic and spontaneous way. The Vikings, with lower mountains and more oblique sunlight, freeze-dried herring with more imperfections.
Closer in time, researchers Bordas and d’Arsonval – in 1906 in France – and American Shackell in 1909, discovered the basic principle of sublimation, using elementary laboratory freeze-drying equipment.
Years later, industrial application began at the Pennsylvania School of Medicine in the works of E.W. Flosdorf and S. Mudd, who freeze-dried the first products for large-scale clinical use, mostly serum and plasma for the army.
Since then, the evolution of this technique has been spectacular, firstly for its almost exclusive pharmaceutical use and then, increasingly, in the food industry, where coffee and other soluble nutrients are at the forefront of freeze-drying.
And so we arrive at creative and modern cuisine, where the factor of conservation is less prized than that of taste. And a freeze-dried product not only maintains its properties intact but also strengthens and multiplies the factor of taste.