There’s a fairly common misconception that the terms “dehydrated food” and “freeze-dried food” are the same. Knowing the difference will help you decide how to store and preserve food for your family.
History of Dried Foods
With any type of food preservation, moisture needs to be removed from the food. Ancient civilizations discovered this and developed the early systems for drying foods that we still use today. Dehydrating is said to have been in practice since 12,000 B.C. Roman and Middle Eastern populations would dry fruits and vegetables in “still houses,” using fire to dry out and smoke the foods.
By comparison, freeze drying is a relatively modern process, though it is said to have started with the Inca Empire. Much more recently, the freeze drying process was refined during World War II as a way to preserve blood plasma, medicine, and eventually food for the troops.
The Difference Between Dehydrating and Freeze Drying
The main objective with food preservation is to remove moisture so that the food doesn’t decompose or grow mold. Removing moisture without destroying the food’s basic composition adds to both shelf life and the nutritional value of the food.
Dehydration in poorly built home dehydrators removes about 70 percent of the water in foods. In this situation, the food is only good for a few months. However, upscale commercial dryers can remove as much as 90 to 95 percent of moisture content. In contrast, home freeze drying with a Harvest Right unit removes 98 to 99 percent of the water in food.
Because of the amount of moisture that remains in dehydrated food, most dehydrated products done at home like dried fruit, meat, and vegetables have a shelf life of one to two years at most. Those same foods preserved with a freeze dryer have a shelf life of 15-25 years.
Furthermore, the nutritional value of dehydrated food is around only 60 percent of equivalent fresh food. This loss is largely due to the heat used during dehydration, which breaks down the food’s vitamins and minerals. However, according to the American Institute of Cancer Research, freeze-dried foods retain the vast majority of the vitamins and minerals found in their original state. In fact, freeze-dried food typically retains 97 percent of its nutrition because of the cold vacuum process that is used to extract the water.
Freeze drying doesn’t change the look or the taste of the food. The above freeze-dried turkey dinner includes big slices of turkey, mashed potatoes, gravy, stuffing, and corn, that looks and tastes the same as if it had just been made fresh. And, the best part is you wouldn’t know if this meal had been freeze dried 15 years ago.
What preservation methods have you tried before? What went well, what didn’t?
Stuffing, if it has a lot of bread, won’t come out quite the same, but otherwise I’m in perfect agreement.
I’ve had some dental work where it was hard to chew for a while. Dehydrating makes jerky or hard fruits as anyone who has had trail mix has experienced. My dehydrated lunchmeat was light and I had no problem eating it – even easier than potato chips but it tasted better and was healthier. I’m not sure if you can dehydrate any dairy, or if you would like the result. Freeze-dried cheese, yogurt, cottage cheese, etc. is great.
I know they talk about reconstituting things after decades, but I’m just happy the kale, chard, and spinach I got fresh last summer is now a nice, nutritious, crunchy snack. And I don’t have to keep it in the refrigerator or freezer!
Some things like spices – basil, parsley – can be dehydrated, but even those are far better freeze dried.
Compare the nutrition labels of the dehydrated vegetables and the freeze-dried vegetables. I’ve done that online for some food storage companies and have found that the dehydrated vegetables have more nutritional value than the freeze-dried. I’m not sure why that concept of comparing hasn’t been pointed out in this article. Unless there have been some technological changes in the freeze-dried process as of late, dehydrated vegetables are the most nutritious. Also, if we do not have vitamins stored in our long-term food storage and rotated properly, we’ll need the best source of vitamins as possible.
Sally, you might be comparing against some commercially freeze dried food companies. But, dehydrating uses heat to remove the food so that heat destroys some of the nutrition. Freeze drying technology allows you to retain 97% of nutrition because it does not use heat to remove the water from the food. The advances in technology are such that you can freeze dry your own quality food at home and not have to add any preservatives in order for it to keep on your shelf, so it also even healthier because of that.
Also, typically serving size is 1 cup. Because dehydrated food shrinks considerably (think grape to raisin), the calories and vitamins would potentially be higher because you can fit more into one cup. Freeze drying doesn’t shrink the food, so not as much gets packed into 1 cup. Following this logic, dehydrated food, would also have higher nutrients than fresh food. Which of course isn’t true :).
To my knowledge you have to dehydrate with temperature below 105 to retain the nutrients
That depends. Some enzymes help at higher temperatures (however generally moisture must exist). Also it depends partly on how much moisture exists in the product when heated and how hot as well as how long. Temperatures under 120 degrees generally do very little harm (and good sometimes). If a product is freeze dried then there is not water to create a chemical reaction with at such low temperatures as 120F.
Many people prefer freeze-dried fruits and vegetables. It is quick to rehydrate and tastes good whether it is rehydrated or not. My issue comes in with how accurate the findings are with nutrition in most advertisements. I’m not sure if it makes a difference whether I’m looking at labels of commercially produced freeze-dried products or not. Best to you.
Other site said freeze dried is COOKED before freeze drying? Is that always true? Have some “raw” freeze dried pet food we assumed was NOT COOKED before freeze drying (Primal Pet)
No. It doesn’t always have to be cooked before freeze drying. Many people do raw meats and freeze dry them.
Correction needed. The Romans weren’t around in “12,000 BC.”
Food does NOT have to be cooked before freeze drying, but consider how and when you will use it. I cook everything that we need to cook before eating because I am preparing food for camping (prefer to do as little cooking as we can get by with) and long term storage for emergencies. After a hurricane, we might not be able to cook our raw freeze dried food. But we can rehydrate it with cool water if we have to, and many FD foods don’t need to be rehydrated (fruits, some raw veggies, cooked meats, cooked veggies).
Could you direct me to the study from the American Institute of Cancer Research? I haven’t been able to find it. Thanks!