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Freeze dry food - Definition and Advantages

Lyophilization or freeze drying is a newly developed food processing and preservation method. It provides the best results among all preservation solutions, in terms of food taste and appearance, shelf life, nutrition values, weight and volume, or preparation method.

Among preservation methods…

Since the oldest time, food preservation has been a concern and necessary for survival ; the process of decay begin early, right after fruits and vegetables, or meats, are harvested. During difficult periods, man could only rely on some preservation methods if he wanted to eat all year round.

The best known method is sun and wind drying, fairly used in Africa and the Middle East. In colder climates, people used to take advantage of severe winter conditions to frost their food (by keeping them in the same snow). Later on, new methods took place : smoking has become the best meat preservation technique …

Another well-known method, still in use today, is appertisation. It refers to the preservation of pre-sterilized food in airtight containers (tin cans or jars for example). Sterilization is a preservation process that kills germs and microbial spores by exposing food to high temperatures (above 100°C). This technique was invented by Nicolas Appert in response to the French army that was in need of a more efficient preservation technique back in 1795.

Freeze drying

Food freeze drying was already used by the indigenous people from the Andes. The freeze drying method that is used today was developed by French inventors Arsène d'Arsonval and Frédéric Bordas in 1906.

This principle was improved during World War II for vaccine transport to avoid refrigeration that was deemed too uncertain. Then, it was mainly used by NASA, to provide a varied and good quality supply of food to astronauts on assignment.

Since then, freeze drying has made itself known to the general public thanks to a daily flagship product : the freeze-dried coffee.

Freeze drying consists first in freezing and dehydrating foods to remove water. As a result, the product takes up less space; but, once rehydrated, it will revert back to its shape. From the freeze dryer to our cup or plate, there are many steps involved to get a freeze dried product. Here is the principle behind it :

1 - Fast freezing of the fresh or precooked product, at an extremely low temperature, around -40°C.

2 - Sublimation of the frozen product : the frozen water evaporates quickly when it is placed under a deep vacuum. Foods are warmed up in that environment. Once 0°C is reached, water in its solid state cannot get back to a liquid state since it is in a vacuum environment, so it converts directly to a gas state. And foods become freeze dried.

3 - Sealing of freeze dried foods in moisture-free packages with oxygen-absorbing material to attain long-term storage stability. Some items can sit on a shelf for 25 years without degrading !

This method is still an expensive operation due to the high energy consumption, but it offers many advantages compared to other food preservation methods.

Freeze drying advantages

Freeze drying is a method that can be applied to any food item (even to ice creams !) … These products are used by people practicing outdoor activities (Backpacking, Mountain biking, Sailing, Kayaking, self-sufficient Running, Trail running …) or by those who just want to be prepared and have a food source for use in survival situations.

Below are the reasons why people use freeze dried products :

- Taste and appearance : freeze dried products taste and look like fresh products. Freeze drying does not shrink or harden the food, it rather preserves its aroma, shape, flavor… Once rehydrated, food products are like their fresh counterparts.

- Shelf life : freeze dried products have a very long shelf life. When the product is properly stored, food can last between 15 and 25 years. Even beyond this period, products will remain safe to eat, their flavor and nutrition values will be just as good as the day they were freeze dried. In comparison, dehydrated food and frozen products only can last 2 years.

- Nutrition values : freeze drying causes only little damage to food. Freeze-dried products maintain around 95% of their nutrients throughout the freeze drying process. Other methods, like dehydration, keep only 60% of the nutritional value because the heat used during the process breaks down some of the food’s vitamins and minerals.

- Weight and space : once the water is removed from the foods, they become very light. For example, the water content of vegetables, fruits, or dairies, exceeds 80%, cooked pasta contain around 70% of water, fish and meat contain between 65 and 70% of water, some products such as butter contain a little amount of water. Additionally, freeze drying is highly space-efficient; it allows you to stockpile more food in your storage space or to carry several units in your backpack.

- Preparation : freeze dried meals prepare easy and quickly, all you need to do is add hot or cold water depending on the menu, wait a few minutes and ‘voila’… your food is ready for eating ! Today, manufacturers are able to offer a large range of freeze dried meals. From breakfast to dessert, every meal can be freeze dried. From aligot to paella, through scrambled eggs and apple sauce, today thanks to the freeze-drying process, you can enjoy eating healthy and varied meals even in the open sea or on top of a mountain.