The Freeze-Drying Process
Freeze-Drying is a method of dehydration drying that uses low temperature vacuum pressure to preserve perishable materials such as fruit and vegetables.
Freeze-Drying works by freezing the material first in a blast freeze at -40 degrees Celsius, then placing the product in a vacuum chamber and slowly reducing the surrounding pressure allowing the frozen water in the material to sublime directly from a solid phase (ice) to the gas stage.
Freeze-drying is a very gentle process taking up to 7 days to complete and once finished products need to be stored completely air tight to prevent them from absorbing any atmospheric moisture.
Freeze-Drying differs from Air Drying and Dehydrating/dehumidifying in many ways;
Moisture content plays a huge impact on the shelf life. The more moisture a product has the less time it will keep. Dehydrated and air dried fruits can loose up to 70-90% of their moisture, however the freeze drying process is able to extract 98-99% of all moisture. We recommend storing your freeze dried goods below 25 degrees Celsius as the cool temperature will also help lengthen the shelf life.
Food Science has proved that Freeze Dried food maintains most of its nutritional value, up to 95% of the nutritional value and 100% of the products fibre, throughout the process, and once rehydrated, is very similar to the nutritional value of its fresh counterpart. This is in contrast to dehydrated food with only 50% - 60% of the original nutrients remaining.
Freeze Dried and Dehydrated foods both taste great, but there is a huge difference in the flavour and feel of the finished product. Freeze Drying essentially uses less heat keeping the flavour as close to a fresh product as possible. The shape and colour of the fresh product is also retained.
Rather than a dense, chewy, “leather” like product, freeze dried fruit/veg is virtually weightless, crisp and crunchy with a concentrated flavour.
Freeze Dried fruit weighs much less than
dehydrated food. On average a freeze-dried product can weigh less than 12% of
its fresh weight, where as dehydrated usually weighs around 25%.