It is pretty common for the terms “freeze dried” and “dehydrated” to be used in each other’s place throughout a lot of content you might find out there. Although they may appear similar when looking at the end result, and both remain shelf-stable for quite some time, the process is rather different. The end results also perform differently when it comes to nutrition, storage, and many other important factors.
For both preservation processes, water is removed from the food. The term “dried” applies here for both types for it is simply the methods for how the water is removed that changes. Essentially, dehydrated foods achieve an average amount of 90% to 95% water reduction, and freeze dried foods achieve up to 98% to 99%!
Food can be dehydrated in one of a couple of ways. Traditionally, food was left in the sun or air to dry for several days when the humidity was low and temperatures were high. It is one of the most prevalent forms of preserving food by ancient cultures. Nowadays, people use simplistic machines with built-in fans to mechanically keep the air flowing in a controlled environment to dry out their food. The machines provide the most optimal amount of heat and flowing air to dehydrate the food at the quickest speed most delicately.
Freeze drying has much more recent roots, having been invented in the year 1906! As a way to preserve medicine during WWII, it didn’t become popular to use for food for a little while longer. While consumers have the option to purchase a freeze drier for indoor use in their homes, the large commercial machines only affordable by industrial warehouses make up the sources of the bulk of freeze dried food available today.
While dehydrating food uses heat to evaporate the moisture out of food, freeze drying takes a little different approach. The food is first brought to below freezing temperatures. It is then subjected to a slow heating process that releases the frozen liquid from the food as a vapor (as a process known as sublimation). The vacuum environment inside the machine then removes the moisture vapor from the food until the food is dried efficiently.
The following topics outline some basic ways that dehydrated foods are different than freeze dried foods:
Foods that can be dehydrated or freeze dried vary.
There is a bit of controversy and debate online in some blogs and articles about which types of foods you can dehydrate vs. which ones you can freeze-dry, allowing more choices in frozen-drying alternatives. At the same time, since freezing dried foods allows more processes to take place and will involve the use of complex types of machinery for water extraction, then, understandably, these types of foods are more expensive than those dehydrated. This is the reason many people feel frozen dried foods have a superior flavor than those dehydrated, which uses heat to remove the moisture, thereby losing flavor, original texture, and aroma. If you plan on keeping the foods in your pantry or emergency food supply until you need them, then weight is not a real concern.
Temperatures during processing are different.
Instead of using heat, freeze-drying uses extremely cold temperatures, such as -40F, then forms a vacuum around the food, and heats and cools the food alternately, to extract 99% of the moisture from the food. Both freeze-drying and dehydrating are methods of preserving foods by removing the water from foods, giving them much longer shelf lives. Dehydrating foods removes around 80% of the water from the food, meaning even if it is not quite as long-lasting as freezing, it is still an excellent method to save foods that you know you cannot use immediately.
The characteristics of the resulting food items are not the same.
Freezing or dehydrating does tend to change a foods natural flavors just a little bit (though often with texture differences, too), and freezing is a better method of preserving the normal flavors and odors of food. Dehydration and basic freeze-drying both involve taking the moisture out of a food in order to make it shelf-stable — a food preservation technique that also makes a food lighter and compact in order to maximize resources in storage and shipment. Dehydrated foods tend to have retained the integrity of their skins or other structures, only to have had them reduced of their moisture. This can lead to chewiness and sometimes a tougher food product. Freeze dried foods, while they can be reconstituted to their original forms and makeup, it is possible to crunch or crumble them while in their freeze dried form.
This information is not only entertaining to learn more about, but it can help with making both important food storage and commercial business decisions. To learn even more about the freeze drying process, and how Shepherd Foods can give you the ingredients you need, visit our website or give us a call today at (801) 798-0344!
This post was originally published on 2/24/22 and updated on 5/17/2022 for accuracy and a larger scope of information.