The basic premise is given away by the name – a process that removes water (‘drying’) to create a dry product. The freezing phase is critical in this process as it allows the product to maintain its shape and high quality. A basic overview of the steps is as follows: freezing the product rapidly, exposing it to low pressure in a vacuum, and removing the ice via ‘sublimation’ (a fancy word that simply means the ice is converted from solid to gas without melting).
You may be wondering what makes this process more superior than its heat-filled drying counterparts. When a product is freeze-dried it keeps its overall structure, colour and flavour profile. The delicate nature of fruits make them susceptible to quality loss if a more conventional dehydration method is used. While you have probably noted that dried fruits (e.g. dried apricots) tend to be chewy and shrunken, these results do not occur in freeze drying due to its low temperature and the loss of liquid.
Besides this sensory element, the nutritional profile is also maintained in the freeze drying process. The higher temperatures used in other methods cause certain nutrients to be lost if they are heat-sensitive. Studies have shown that freeze drying fruits is the best method to maintain the highest quality product.
The end product is only 1-2% water and is therefore dry enough to be turned into a powder, whereas more conventional dehydration methods only remove 90-95% water. Freeze dried powders are prone to clumping if exposed to moisture. This is particularly significant for fruits due to their high sugar content as the clumps could be paired with stickiness. The benefits of being able to enjoy so many different foods on the go and all year round far outweighs this hurdle. Clumps can easily be avoided by tightly sealing the product in foil sachets for freshness and enjoyment whenever you please!