Freeze drying is defined as which of the following?

• A. A method of removing water from food by boiling
• B. A process that improves flavor only
• C. A method of removing water from food, using sublimation
• D. A method of freezing foods for storage

Answer: (C)

Freeze drying removes water from food by sublimation under low pressure after the product is frozen. The ice turns directly into vapor, bypassing the liquid phase, which helps preserve texture, nutrients, and overall quality. The process starts with freezing, then lowering the pressure and applying a little heat so the ice sublimates. This is why describing it as removing water by sublimation is the best fit. Boiling removes water by evaporation, not sublimation, so it’s not how freeze drying works. It’s not simply about improving flavor or just freezing foods for storage—the key idea is removing water through sublimation while the product stays structured.