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How is freeze-drying connected to the sublimation of water?

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Diagram showing four physical states of matter: solid with tightly packed molecules, liquid with loosely packed molecules, gas with widely spaced molecules, and plasma with free electrons and nuclei, each labeled with descriptions and an arrow indicating increasing energy. — phase States of matter.

Freeze-drying is a method of dehydration that relies directly on the process of sublimation.

In this process, a substance—such as food—is first frozen. Once in a frozen state, it is placed under a high vacuum. Under these specific conditions, the water contained within the food transitions directly from a solid to a gaseous state without ever passing through the intermediate liquid phase.1

By bypassing the liquid phase, freeze-drying allows for the removal of moisture while preserving the structure and quality of heat-sensitive products, as it avoids the damage that can occur during traditional thawing or heating processes.2