Updated: Aug 22, 2020
When you think of freeze-drying, you probably think of outdoor food instantly, right? But have you ever thought what is actually involved in getting the food dried and ready for you to re-hydrate? Well read on and see what is involved with drying the food, and see why it is such an excellent option for the food we take adventuring.
I guess the place to start really is, a little bit of the history of freeze-drying. You can trace freeze-drying back to the 15th century in its most basic form. The Inca people would store their crops in the mountains above Machu Picchu. The freezing cold temperatures and the low air pressures led to the moisture slowly turning to vapour and leaving the food effectively freeze-dried.
The modern techniques were developed during World War 2 due to a lack of refrigeration when transporting blood from the US to Europe for the wounded soldiers. It was then developed commercially for the medical field. NASA then made the freeze-drying process widely popular when it wanted Ice Cream in space in true American style.
So, "what actually is freeze-drying?" Well, simply put, the food is frozen and then dried, right? There is actually a little more to the process. So let's see what is that looks like;
1- First, the food is frozen; however, it is frozen to a freezing cold minus 50°C. This is to ensure all the water is frozen in the food.
2- The pressure in the freeze dryer is lowered to about 600 millibars. For some context, that's about the air pressure at the summit of Aoraki/Mt Cook.