Final answer:
Freeze-drying, also known as lyophilization, is a food processing method that involves freezing the food, then creating a vacuum to remove moisture via sublimation. The vacuum speeds up the dehydration process and causes the food to freeze because it lowers the boiling and sublimation points of water.
Step-by-step explanation:
The methods of processing foods mentioned in the Food Safety videos are freezing, canning, and dehydrating.
Understanding Freeze-Drying (Lyophilization)
Freeze-drying, or lyophilization, is a method used to preserve food by removing water content while maintaining the food's structure and nutritional value. The process involves freezing the food and then reducing the surrounding pressure to create a vacuum. This allows the frozen water in the food to sublimate directly from ice to vapor. The vacuum speeds up dehydration because it lowers the air pressure around the food, which in turn decreases the boiling point of water. This makes it easier for the water to evaporate, even at lower temperatures. As the pressure decreases, the temperature at which water sublimates also drops, which is why the food initially freezes. This method is effective for preserving food and controlling microbial growth because it prevents the degradation that can occur with traditional heat drying.