That's a great question that we are asked often! So often that we've dedicated an entire blog post about it, which you can read about here.
In short, dehydration in its most basic form is heat and airflow. Products are placed on trays where warm air is circulated throughout the dehydrator to slowly dry out the food and usually removes between 90 to 95% of water.
Freeze-drying is a more complicated process as it involves freezing all food to a very low temperature, usually between -30C and - 40C; after this a vacuum is pulled and then the temperature within the machine is slowly heated up so that the moisture transitions directly from ice to water vapor without ever becoming a liquid. This process is known as submlimation.
No, absolutely not! We do not add any artificial preservatives to our food. Rather, our meals are naturally preserved by removing the two main culprits that cause food to spoil: oxygen and moisture. The freeze-drying process is what makes our food shelf-stable.
While we highly recommend using boiling water (especially if you are out in the backcountry using water collected from rivers/streams/lakes), the meal will rehydrate with warm water. If you are using warm water rather than boiling water, you may need to stir more thoroughly and wait a little longer for the water to be reabsorbed.
If you are using cold water, we suggest rehydrating your meal at least 30 minutes before you plan to eat so that the food has fully absorbed the cold water.