Freeze-dried products must be hermetically sealed immediately after receipt. The packaging must isolate the product from oxygen in the air and the action of light, prevent the sorption of moisture by the dried product from the environment, protect against mechanical damage, protect against loss of natural odor and the acquisition of strangers. The most acceptable for these purposes are containers made of polymeric materials, the main advantages of which are relatively high barrier properties, low weight and rigidity, good appearance and low cost. The best option in this case are polymeric materials based on aluminum foil cached by polymer films. Products should be packaged immediately after drying in conditions of low oxygen and moisture content.
Oxygen is removed from the package by various methods: physical, chemical or biochemical. Of the physical methods in production practice, the most widespread is a single vacuuming of packaging with the subsequent introduction of nitrogen into it. Quite effective chemical methods include the removal of oxygen from the package as a result of its reaction with hydrogen, which occurs with the participation of a catalyst, which is used as palladium. It is also possible to pack products in special sealed chambers with an inert gas, where this is controlled by a microprocessor.
It is now generally accepted that some changes in the properties of the feedstock occur in the freeze-drying process, but they are minimal compared to changes in canning by other methods.