While the consumer may not know the difference between these two methods of long term food storage, the sellers of freeze-dried and dehydrated foods do. Or, they should. If you are reading this then you may not. Allow us to educate you. There is indeed a difference between the two methods. But first, let's discuss the similarities.
Both dehydrated foods and freeze-dried foods are capable of lasting for years after they are packaged, assuming they are stored correctly. The correct packaging for long term food storage is a pouch capable of preventing both air and moisture from entering into it. Mylar storage bags remain the best method for storing food for longer than a year. Mylar pouches stored in an airtight container have been recorded to last 30+ years and retain the flavor the whole time. During both processes, the majority of the food’s moisture is removed before packaging. But how the moisture is removed is different for the two processes. The two methods of water removal also affect the taste and nutritional value.
When food is dehydrated, it has been subjected to low heat over an extended time. As a result, most of the food's water has evaporated. Compared to freeze-dried foods, dehydrated foods are much cheaper to make. Food can be dehydrated simply by placing it in sunlight for a few days. This is how we get things like sun-dried tomatoes. An easier method is to use machines called dehydrators. These machines circulate warm air which causes the water in the food to evaporate and then it gets expelled through the machine's vents. An oven on low heat can also dehydrate food if you remember to open it occasionally to allow the evaporated moisture to escape. For the longest shelf life, food should be dried until 95% or more of the moisture is removed. This percentage can be lower, but the more moisture dehydrated food has, the shorter the shelf life. The pros and cons of dehydration are as follows;
- Less susceptible to outside elements
- Shelf-life up to 15 years
- Pack friendly
- Dehydrated food costs less than freeze-dried food
- Less nutritional value
- Takes longer to rehydrate
- More water required to rehydrate
- Generally packaged without any seasoning or additional ingredients
Because of the hardier nature of dehydrated foods, we recommend a bag with a 3.9 mils thickness, for example, the 308.
Like dehydrated foods, freeze-dried foods have had most of their moisture removed, but where dehydration uses heat, freeze-drying uses cold. This difference results in higher nutrient content and more flavor. In the freeze-drying process, food is subjected to extremely low temperatures (-40F or colder) until frozen. Then once frozen, a vacuum is formed around the food, and then the temperature is slowly raised. The frozen water goes through sublimation or transfers directly from a solid to a gas state. This process requires specialized machinery that is typically found in commercial settings.
- Shelf-life up to 25 years
- Lighter in weight
- Higher nutritional values
- Less water required to rehydrate
- Packaged containing a multitude of ingredients and seasonings
- More susceptible to outside elements
Since Freeze-dried foods are more susceptible to degradation, you should be using a thicker, 4.7 mils bag like the 306.
Preservation of food for extended lengths is only achievable when the food is guarded against the elements. As long as the moisture is removed from the food, either through freeze-drying or dehydration, and then stored in an airtight container, it can last as long as 15-30 years.