The Processes
Freeze drying is a process of sublimation, which is expensive, labor intensive, and done in a professional atmosphere. Sublimation is when a solid, like our peas, changes directly to a vapor without first going through the liquid, or water, phase. During the freeze drying process, the freeze drying is controlled to keep the product temperature low enough to avoid any changes in the dried product appearance or characteristics. So, basically our freeze dried peas look the same, or very nearly the same, as fresh green peas, but the liquid has been removed from it without changing the shape and overall look of the peas. Dehydration removes water or moisture from our food product, like our peas, usually with the presence of heat, which forces the moisture out of the peas, but doesn’t cook the food. Dehydration is something that can be done at home under the right conditions, and there are dehydrators that can be purchased.
Finished Product
Freeze drying preserves the overall shape and taste of the original food, and the result is a lightweight (and sometimes fragile), crunchy, and crispy product that can be eaten without rehydrating. Dehydrating causes the product to shrink or shrivel, making it a more hearty, leathery, and tough product, and it general needs to be rehydrated before consuming.
The Taste
Freeze dried foods have a tendency to be crunchy and flavorful, right out of the bag. Dehydrated foods are usually pliable or leathery, and cannot be eaten (with the exception of fruits) without reconstituting itself or in a recipe.
Moisture Content
Freeze drying removes 98-99% of moisture, and dehydration removes 90-95% of moisture.
The Weight
Freeze dried foods weigh a lot less than dehydrated; however, freeze dried foods are more fragile and need to be stored carefully, or they will easily become powder or get squished easily. Dehydrated foods are substantial, compact, and do not break down as easily.
The Cost
Freeze dried foods are more expensive than dehydrated foods due to the involved, labor intensive, and expensive equipment used to freeze dry fresh or IQF fruits, vegetables, beans, etc.
Cooking
Freeze dried foods can be eaten out of the package, if desired, or if they are reconstituted, they only need water. Dehydrated foods need to be cooked (with the exception of the fruits), and could take minutes to cook, depending on the product.
Children and Eating
Freeze dried foods are extremely kid friendly, and will be eaten without any issue, right out of the packaging. Some kids, who have issues with textures, love freeze dried fruits and vegetables because they’re crunchy and flavorful. Dehydrated foods are typically harder for children to eat right out of the packaging, without rehydrating it first. And then, the dehydrated food will most likely go into a family friendly dinner, entree, casserole, or soup recipe.
Space
After freeze drying, the products retain the look and size of the fresh; so, it will take up more space. It is also easily crushed; so, it needs to be stored carefully. Dehydrated foods shrink and are of a tougher constitution than the freeze dried; so, it is easily stored in large bulk and is compact.
Shelf Life
Freeze dried foods, because so much moisture is removed from it through the freeze drying process, is said to last a little longer on the shelf, in ideal conditions, than dehydrated. Dehydrated foods, due to the drying process, have more moisture left in the product, which can make it more susceptible to moisture than freeze dried, when stored in ideal conditions. A lot of a product’s shelf life is determined by light, temperature, and quality of seal the package (what we call the Big Three) of product has. Regardless of what your store, it will last if you keep it carefully and with awareness of the Big Three.