The Science of Freeze Dried Foods

Food is a vital tool for human survival. And, because of this, food preservation technologies are used to prolong the life of foods. Preserving food properly is key to self-sufficient living, especially in the wake of a man-made, natural, or financial crisis.

There are various methods of preservation techniques. In this article, we’ll examine the science behind freeze dried foods and their preservation process.

Photo Credit to Jo Naylor on Flickr

What is Food Preservation All About?

Preserving food is an age-old practice. There are two basic ideas behind food preservation, in all forms:

It slows down bacteria activity responsible for causing diseases.
It helps to kill disease-causing bacteria altogether.

Freeze-drying is one of the common techniques used to preserve foods. With this technique, a special method of drying is used in order to remove the moisture from the foods. Freeze dried foods are flash frozen, as opposed to be “dried out” using heat. Because of this, the effect on the taste of the foods is much less than that of normally dehydrated products.

How does flash freezing work? During the freeze-drying process, the products are frozen using extreme temperatures. They are then placed inside an extremely strong vacuum chamber. This causes the moisture (water contents) within the food to sublimate, meaning: turn from ice straight into vapor.

An Experiment in the Science of Freeze Dried Foods

For this experiment, you’ll use your freezer as your home vacuum chamber. Although it will take a week for the process to complete, it’s a great way to learn to freeze dry your own foods for better self-sufficiency. Here’s everything you’ll need for this freeze drying experiment:

A perforated tray – metal mesh tray, cake-cooling rack, etc…
A product to freeze-dry – apples (best), carrots, potatoes, etc…

Note: If you don’t have a perforated tray, a simple plate or cookie sheet will work. However, this experiment will take quite a bit longer to complete that way.

Freeze Drying Experiment

Follow these simple steps below to begin the experiment:

Use a knife to cut your food product as thin as possible. Paper-thin is best. Just keep in mind that the thinner the slices, the less time it will take to complete the freeze drying process.
Arrange all of the food slices on your tray, without stacking them on top of each other.
Place the tray in the freezer. The entire process needs to be done fairly quickly. If not, your apple and/or potato slices will begin to discolor.
Check your slices in about 30 minutes. They should all be frozen solid. Leave them in the freezer.
Take a look at your slices often over the next week. The moisture contents will have sublimated away. This means that the solid water in the foods will have converted straight to water vapor, never actually hitting a liquid state.
Depending on just how cold your freezer gets, the food will completely dry out after about a week. To test, take one of your slices out of the freezer and allow it to thaw out. If the slice turns black almost instantly, it wasn’t completely dried out yet.

Once the products are completely dry, you’ve created freeze-dried food. To reconstitute them, or put them back to their original form, put them in a bowl or cup, and add some boiling water. You can also add room temperature or cold water, and place them in the microwave until the water is boiling. And, that, my friends, is the science of freeze dried foods.