Freeze-dried food – what is itand how is it made?

Mankind knows many techniques of food preservation – we preserve it, for example, by using preservatives that are not necessarily good for our body, by drying, smoking, pasteurization, freezing, etc. Unfortunately, most of these methods have many disadvantages because either they are associated with certain losses (for example, the loss of certain micronutrients or taste attributes) or addition of various chemicals. However, there is a technology thanks to which food retains almost all of its nutritional values, and additionally it does not change its taste at all! We are talking about freeze drying – check how freeze-dried food is made and why and when it is worth having it on hand!

WHAT IS FREEZE DRYING?

Freeze-drying technology is relatively new because it was first used during World War II – the US military was looking for a way to transport food easier (to be more specific, its weight was the concern) and to extend its shelf life.

Freeze drying involves ice sublimation, and the whole process goes as follows: first, a product, for example strawberries, is placed in a freeze-drier. Then the temperature inside the freeze-dried is reduced to -40°C. When this is achieved, a vacuum is created inside the freeze-drier, thanks to which the aforementioned ice sublimation occurs, i.e. water evaporates omitting the liquid state. The last stage is drying, which takes place at a temperature of 40-50°C. The process takes several hours, and the water content in the finished product is 1-2%. Thanks to such a low water content, freeze-dried products can be consumed even many years after being subjected to freeze drying. Interestingly, apart from water, the product does not lose any of its nutritional values, nor does it change its look or size. Even the taste does not change drastically. The difference is only in the consistency, which after freeze drying is crunchy.

WHAT PRODUCTS CAN BE FREEZE-DRIED?

The answer to this question is simple – you can lyophilize literally everything on your plate, from vegetables or fruits, through herbs, mushrooms, meat, to ready-made dishes, such as spaghetti.

The use of freeze drying is very broad and does not only apply to food. During World War II, the US military also freeze-dried … blood plasma! The process is also used by pharmaceutical companies, etc.

HOW DOES FREEZE-DRIED FOOD TASTE?

It depends on how we eat it. For example, a freeze-dried strawberry is dry and crunchy at first. However, after a while it will take on water, which will make it soft and its taste will not differ much from a strawberry picked from a bush.

Freeze-dried food can also be poured over with water, thanks to which it will become moist and taste similar to a ready-made dish. However, it may differ slightly in consistency due to the fact that the water that our freeze-dried dish will absorb may be decomposed differently than in the same product before subjecting it to freeze drying.

WHEN AND WHY IS IT WORTH USING FREEZE-DRIED FOOD?

Freeze-dried food is a great solution, for example, for multi-day mountain hikes because it is very light, so it does not burden your spine when you carry it in your backpack, and what’s more you can store it for many days in various conditions – it is resistant to both low and high temperatures. In addition, it is characterized by high nutritional values, almost the same as the food had before it was subjected to freeze drying.

Freeze-dried food can also easily replace fresh fruit, for example in your muesli – after pouring milk or yoghurt over it, it will have a similar taste to that before freeze drying and the same values, with the difference that you will not have to buy and add fresh fruit to your muesli every day.

BRIEFLY ABOUT THE HISTORY OF FREEZE DRYING

Interestingly, a process similar to freeze drying was used by the Chilean Incas – they left potato tubers high in the mountains, where they froze at night, and the low pressure caused a phenomenon similar to ice sublimation. The morning sun helped evaporate it, and the food from then on could be stored longer. Of course, today’s technology is much more efficient, but the process itself is quite similar.

Modern lyophilisation took place much later because as mentioned earlier, this technology was first used during World War II. Another great moment for freeze-dried food was the time when mankind made its first flights into space. Astronauts faced a rather trivial problem, as it might seem, i.e. the problem of food in space. Many forms of serving food in space have been tried, for example, food in tubes resembling those in which we buy toothpaste today, or cubes that were dried using traditional methods. Unfortunately, they worked quite poorly and did not appeal to astronauts, and in addition, the cubes could be a danger to both crew members and equipment, because they left crumbs that wandered in the cabin vacuum. After many trials, NASA finally opted for freeze-dried food because it was easy to prepare, did not leave crumbs, and additionally retained almost all its health properties. Taste did not change either, which made it very appealing to astronauts!

DO NOT BE AFRAID OF FREEZE-DRIED FOOD!

Freeze-dried food is a huge technological achievement! It keeps its freshness for many years, it can be stored in a home pantry at room temperature, and the only condition that such a pantry must meet is low humidity. Of course, an ordinary zip lock bag can help us minimize it!

It is worth taking such food, for example, for a weekend in the mountains or simply add it to your muesli and other dishes – once you buy freeze-dried food, you can store it for a long time, thanks to which you are not dependent, for example, on the seasonality of some fruits or vegetables!