I have the opportunity to talk to people about storing foods from time to time, especially since we are off grid and do not use refrigeration very often, we have a couple of small dorm sized fridges but rarely plug them up, I also have access to my neighbor’s refrigerator. I have heard more than one conversation where people confuse dehydrated food with freeze dried foods. They are in fact, two different things.
What they do have in common is the food has had most of the moisture removed, where they differ is the methods that are used to dry the food, and the texture and weight of the finished product. Wikipedia says:
“Drying is a method of food preservation that works by removing water from the food, which inhibits the growth of microorganisms and hinders quality decay. Drying food using sun and wind to prevent spoilage has been practiced since ancient times. Water is usually removed by evaporation (air drying, sun drying, smoking or wind drying) but, in the case of freeze-drying, food is first frozen and then the water is removed by sublimation.”
Typically food that is dehydrated shrinks and becomes more dense, though lighter because of the water weight being removed. Foods that are freeze dried will look more like the original food, there is less shrinkage, the main difference is the texture, the freeze dried food will be lighter (in weight), less dense, and will have a light crunch if you eat it in its dehydrated state. It also returns to a more natural/original form when rehydrated.
Dehydrated food is simply food that has had its moisture reduced, period. This is something that anyone can do. Freeze dried food requires much more high end equipment. The food is frozen in the presence of a vacuum. This process causes the moisture in the food to go from a liquid state to a gaseous state, skipping the frozen state, this is called sublimation. I am simplifying this quite a bit, needless to say that most of us, the ordinary public, will not be able to freeze dry foods at home.
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