How Much Water For Freeze-Dried vs. Dehydrated Food
Freeze-dried foods have 98% of their water removed. This reduces the food’s weight by about 90%. Dehydrated foods have 95% of their water removed for vegetables and 80% for fruits.
Freeze dried foods retain their original color, form, size, taste and texture. Dehydrated foods will shrivel in size as the moisture is removed.
How is freeze-dried food different from dehydrating?
Answer: The temperature used to removed water. Freeze-drying uses cold temperatures and dehydrating uses hot temperatures. In the freeze-drying process, fresh or cooked foods are first flash frozen. Moisture is then removed in a vacuum chamber, as a low-level heat is applied to evaporate the ice without returning it to a liquid form. Since the food remains frozen during the process, the food’s cell structures do not change.
The food dehydration process begins with quality vegetables, fruits, or meats. They are typically sliced thin, about 1/8 to 1/4 inch, and then are slow ‘cooked’ at temperatures ranging from 130 to 145 degrees Fahrenheit. Times vary, but typically are in the range of 12 to 24 hours until sufficient moisture has been removed from the food.
Feeze-dried foods rehydrate quicker and dehydrated foods condense further, allowing more to be stored in less space.
I recently received a good question from someone who asked… “How much water does it take to cook one serving of dehydrated food versus one serving of freeze dried food. The more it takes to cook the less you have to drink.”
Here are my thoughts…
It does take more water to reconstitute freeze dried food than dehydrated food. I randomly pulled out a few freeze dried food packets that I have on hand here, so that I could read the directions. The average amount of water required is a bit more than 1 cup of water per serving (which you would heat up first). On the other hand, some dehydrated food can be consumed without re-constituting with water (particularly fruits or meats). My experience with re-hydrating foods that I have previously dehydrated, are that I tend to use less than 1 cup of water per equivalent serving of vegetables than a freeze dried food.
Overall, I do not believe that there is a significant difference in water consumption between the two methods, except for those dehydrated foods that are consumed without adding water. On the other hand, for those same foods, your body must use some of its water content to digest and process that same food… so in the end is their actually a difference?
I’ve always believed in diversification of food storage types. Store bought canned foods, store bought jar foods, home canned foods, foods that don’t require special treatment (e.g. pastas), long term foods sealed in 5-gallon buckets (e.g. rice, beans, wheat, etc.), freeze dried packaged foods, and dehydrated foods (great for home garden processing)… just to name a few.
I personally like the taste of freeze dried food better than dehydrated food, and its reconstituted ‘shape’ is basically identical to the original. It costs more. But it’s easy and simple to deal with.
I suggest that if someone is looking at the differences between freeze dried and dehydrated with regards to the water that is necessary versus the availability for drinking water… then you ought to be very concerned about your drinking water situation. The earth is abundant with water, although a small percentage is suitable for drinking. The thing is, if you don’t live near a source of fresh water (other than municipal sources), you MUST factor in the amount of water you will need in a survival situation. It’s not hard to store enough for a month. It gets more difficult though when you consider long term. Water is heavy. It’s hard to transport, requires sturdy containment, and it takes up space. But now I’m getting side tracked and off topic…
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Words of wisdom from the off-grid guy:
Place your freeze-dried foods and dehydrated goods within a mouse/rodent proof container. In the Park Service and Forest Service, we used to store sealed food caches within galvanized steel garbage cans with tight-sealed lids tied or bungied into place. I did not do this one time to a personal cache of leftover freeze-dried food and it was raided by mice within a month. It cost me $50.00 back then. Learn from my mistake and rodent-proof your stash.
When eating a steady diet of dehydrated and freeze-dried food, eat a handful of dehydrated fruit each day and drink lots of fluid with it in order to prevent constipation. Even healthy young men and women were getting side-lined by debilitating cases of constipation while eating a steady diet of c-rations and MREs while fighting fire. Maintain your daily intake of fiber and water to clean yourself out.
Do not eat too much dried/dehydrated food in one sitting. If you drink water and the partially digested mass reconstitutes within your stomach, it can be very painful.
Never pass up an opportunity to eat a handful of either fresh greens or fresh fruit at least once a day.
After 5 or more days in the backcountry eating dehydrated and freeze dried rations, your body will crave fats, protein. You will be tempted to go into the first steakhouse you see and order a decadently sized steak and other fat-laden dishes. DON’T EAT THE STEAK. Most of the time your GI tract will be in a state of shock at the sudden influx of concentrated fat and protein and the steak will rebound. Ease your GI tract back into front-country food gently. Stay away from deep-fried foods, gravy and cream sauces for a few days and keep the portions small. It used to take me about 3 days for my GI tract to get back to normal.
Most of the time, we are thrust into a situation where we switch to the backcountry diet suddenly. The urge to gorge ourselves when we are in a restaurant after such an experience is a normal reaction. Remember these things if/when you go on a backpacking/mountaineering trip.
Quote: “Dehydrated foods have 95% of their water removed for vegetables and 80% for fruits.”
Where do these numbers come from? Do you have some references?
While searching (Googling) for information regarding ‘professional’ dehydrated food and the moisture content thereof, I came up with these numbers on average from a number of sources. No doubt that opinions and sources will vary.
I love this post… I will be reading more of your blogs . thank you