The process of freeze drying food is known as Lyophilization. This is a type of food preparation where all the moisture has been removed to increase its shelf-life, while also increasing its flavour, texture and nutritional value by helping to preserve nutrients such as vitamins and minerals. In addition, freeze-dried food often contains fewer preservatives than canned or processed foods.
A special machine called a freeze dryer is used for the extraction of the water by first freezing the food to around -35 to -45 degrees celsius. Once frozen, the freeze dryer creates a vacuum in the food chamber. As the food is gradually warmed, the water crystals that form in the food are then converted to vapour using a process called sublimation.
When dry, the food is then ready to be placed in a vacuum sealed container that are both moisture and oxygen proof. This ensures that the food stays fresh until opened.
The whole process takes around 20 – 40 hours.
The resulting freeze-dried food is lightweight, easy to store, and can be rehydrated quickly by adding water. Freeze-dried food is commonly used in camping, backpacking, and emergency preparedness, as it can be stored for long periods of time without refrigeration and provides a source of nutritious food in a compact and convenient form.
Freeze-dried food is great as a convenient light-weight meal to take camping as a lot of the manufacturers store it in mylar bags. They usually sell larger portions in tins which are probably too bulky to take camping but would be great to store at home.
Freeze-dried food is very light due to the fact that all of its moisture has been removed. To prepare the food for consumption, all you need to do is add boiling water to the bag, wait for a few minutes for the water to rehydrate it and you end up with an instant meal.
Unfortunately the cost of these dryers is usually too high for the average person to justify. The average cost of ready-made freeze-dried meals is also usually a lot higher than other forms of preserved food.
Some common examples of freeze-dried foods include fruits, vegetables, meats, soups, and desserts but you can freeze-dry any food and even whole meals. What better way to store excess food than popping it into the freeze dryer. Maybe you’ve made a few big apple pies, just split it into meal size portions along with a helping of custard and freeze-dry it all.