Whoever wants to extend the shelf life of food has various options to choose from. Besides freezing and canning in glass jars, freeze-drying is a good solution to ensure that foods are more usable for longer periods. This process is suitable not only for fruity foods like fruits and berries but also for hearty foods such as meat and vegetables. But how exactly does freeze-drying work, and what advantages does it have?
Freeze-Drying - What Is It Exactly?
Freeze-drying belongs to the drying methods used to increase the shelf life of foods. During freeze-drying, almost all water is removed from the food. This process uses the principle of sublimation: due to its special physical properties, frozen water immediately transitions from a solid state directly into a gaseous state when it is in a vacuum. To preserve fruity or hearty foods through freeze-drying, they are first frozen at very low temperatures. Then, a vacuum is created so that the water contained in the food directly transitions from a solid to a gaseous aggregate state. The water vapor released during sublimation extracts thermal energy from the surrounding environment. Therefore, heat must be supplied again to the refrigeration chamber. Thus, after freeze-drying, a food product results that is very similar to its original state but contains almost no water. This allows it to now last much longer. Depending on which foods are involved, freeze-drying can take up to 24 hours. It is considered the most gentle drying method for foods, although it is also quite expensive. The process is often used when instant coffee is produced. But also berries and other fruit varieties are sold freeze-dried in stores.
Advantages of Freeze-Drying
In principle, foods can also be dried much more simply, such as by drying with hot air or directly in fresh air. These drying variants are much simpler and consume less energy. Typically, many dried foods like dried fruit or dried meat are produced using simpler methods. However, other drying processes have a disadvantage: they significantly change the food. This is especially true for structure, because the fruit and meat shrink almost completely. But also the taste changes, as the aroma compounds in the food react with the oxygen in the air. Furthermore, vitamins are destroyed by heat. During freeze-drying, the frozen foods remain rigid and cannot change their structure. The dried cellular components remain as a shell and can later absorb water again. Since hardly any reactions occur on a molecular level during freeze-drying because of the missing ambient air and very low temperatures, the aroma compounds are largely preserved. Therefore, it is due to the multitude of advantages that freeze-drying, despite higher costs, is a very popular drying method for foods:
- The drying process is very gentle as the temperatures during drying are low
- The structure of the food is well maintained
- The shelf life of freeze-dried foods is very high
- The quality is better than that of foods dried with other methods
The greatest advantage of freeze-drying lies clearly in the fact that the foods are dried in a very gentle manner. Therefore, not only does the structure remain almost completely intact, but also vitamins are hardly destroyed. The shelf life of foods can be significantly extended through freeze-drying. After drying, the foods can usually be stored for several years. In terms of quality, freeze-dried foods differ clearly from those treated with other drying methods.
Freeze-Drying Has Its Disadvantages Too
Naturally, freeze-drying also has a few disadvantages that cannot go unmentioned. For example, the process consumes a lot of energy and takes significantly more time than other drying processes. The equipment needed for freeze-drying is relatively expensive. Although smaller freeze-dryers are available in stores for private use, the acquisition costs for them are also very high. Private households can hardly carry out true freeze-drying due to financial reasons. However, individuals or companies have the possibility to realize freeze-drying with Paradise Fruits. The Paradise Fruit GmbH allows for experimenting with one's own recipes in their modern equipped test facilities. Raw materials can also be processed in the company’s lyophilization plants. Small batches are just as realized as large production volumes.
Which Foods Are Suitable for Freeze-Drying?
Not all foods are equally well suited to be freeze-dried. The best option is for foods that contain a lot of water, such as fruits like bananas, apples, grapes or berries. Also vegetable varieties like potatoes, carrots, turnips, and sweet potatoes can be preserved through freeze-drying. In addition, the process is even used for hearty foods: cooked meat, cheese, and even complete meals can be freeze-dried. Suitable are not grain products such as bread, cookies, or cakes.