EN FR ES DE PL

The freeze-drying process

July 07, 2016

The freeze-drying process

What is the freeze-drying all about?

The market of freeze-dried food has flourished in the last years, being actually considered the best food preservation method at the moment. It has expended well beyond serving the market for soldiers and astronauts, to being very popular among trekkers, bikers, climbers, sailors and people eager to stash some food in their house in case of emergency.

Freeze-dried food is lightweight, does not go bad, it’s convenient to use and it’s up to 90% lighter than the original product. But how does it get to be like this?

The first step of the freeze-drying process is freezing the product. Then, the surrounding pressure is reduced resulting in a vacuum. The temperature is slowly augmented and the frozen water content sublimes directly from the solid phase to gas phase. This process is called sublimation and it takes between 16 to 24 hours, depending on the size of the product.

Herbs

Once the water is removed from the product, this one becomes very light, losing over 90% of its original weight. This makes food transportation much easier. The moisture content is reduced to 2% which inhibits the action of microorganisms and enzymes. In a hermetic sealed packaging the product can be stored at room temperature without refrigeration for many years.

Most of the nutritional benefits of the products remain intact. Nutrients are reduced only by the process of sublimation when some of them are lost with the water that evaporates. Nevertheless, 98% of all nutrients are maintained. The method is so good, that it's not necessary at all to put any artificial additives to the product as preservatives, colorants, taste enhancers or synthetic vitamins.

Preparing herbs to freeze-drying

The benefits of the freeze-drying process can be summed up simply: it allows the maintaining of the nutritional qualities, original form, size and taste of all ingredients. The food is easy to store, does not require refrigeration and has a long shelf life.

There are different ways to prepare a freeze-dried meal. Some prefer to freeze-dry all ingredients first and then mix them together. This method can cause that you don't reach the right taste of the meal and here's where artificial additives come up. LYOFOOD wanted to go for that real taste of a homemade meal. There is no place for industrial cooking. We cut all ingredients into bite-sized pieces. Consequently the meals not only taste like a homemade dish but they also look like it. Furthermore every meal is cooked before it is freeze-dried - just as a normal dish is prepared.

How it all started

Apparently the Peruvian Incas first applied a form of freeze-drying in order to conserve their food. They were bringing their potatoes up in the mountains, where the high altitude, the low pressure and fresh air “vaporized the water.” The potatoes froze during the night and then during the day with low pressure and rise of the temperatures, the ice from those frozen potatoes started to evaporate - just like inside freeze-drying vacuum chambers.

Freeze-dried food was first applied in the late forties and fifties of the twentieth century, when the threat of the Cold War looked into the eyes of ordinary, however wealthy American citizens. Information about nuclear armaments from the USSR and the fear of nuclear weapons resulted in the need to build shelters for the civilian population and the possibility of surviving in such a shelter in case people need to stay there for a longer period of time.

Then, at the request of U.S. government, first attempts have been made in order to produce food that can be used in the extreme conditions to effectively replace the traditional cuisine. The only method used until the 50’s was food freezing. Even though the lyophilisation process was already known, it had been successfully used only in the production of medicine and vaccines. The next important event that could be linked to the success of freeze-drying as a method of preserving food is the conquest of space. In the space travel era freeze-dried meals were an indispensable element of the astronauts’ diet during their travels. After being proved in such extreme conditions freeze-dried meals have been also chosen as food for special troops.

These examples show how unique freeze-dried food is and that it is simply irreplaceable in extreme conditions. Freeze-dried food has successfully stood all challenges and revolutionized the food industry. Freeze-drying has found its niche in the food processing industry and has a stable place in high quality spices, fruits and meals.

Good to know

The process of freeze-drying fruits and vegetables causes only little damage to the product’s structure and studies show that the antioxidant phytochemicals found in fresh fruits are retained at levels almost as high after freeze-drying. Dr. Gary Stoner has been researching since the 1980s how the phytochemicals in freeze-dried fruits, such as raspberries, strawberries and blueberries, might protect against different types of cancer.  

Raspberries

Gary Stoner is Professor of Medicine at the Medical College of Wisconsin, Division of Hematology and Oncology, specializing in the fields of chemical carcinogenesis and cancer chemoprevention. His laboratory developed a “food-based” approach to the prevention of esophagus and colon cancers in animals and in humans. Most researches were done using freeze-dried black raspberries, due to their high antioxidant potential and their high content of anthocyanins and fiber.

Using freeze-dried fruits and vegetables is a good method for making sure you get all the antioxidants and vitamins your body needs. At home or during traveling, adding them in the cereal in the morning or eating them as snacks during the day could provide you with the necessary nutrients you might not get otherwise.

Strawberries and freeze-dried strawberries

 
Photo credit:
Przemek Skrzypek / LYOFOOD freeze-drying factory

References:
Amercian Institute for Cancer Research, “Freeze-Dried Fruits Are a Good Health Choice?", May 2006

The Vegetable and Fruit Improvement Center (VFIC)

 





Leave a comment

Comments will be approved before showing up.