Final answer:
To clarify, using dry nitrogen when breaking the vacuum during dehydration indeed slows the process. In freeze drying, lower atmospheric pressure speeds up dehydration and results in the freezing of the food because the evaporation of water lowers the average kinetic energy of the remaining molecules.
Step-by-step explanation:
It is best practice to use dry nitrogen to break the vacuum when dehydrating by the triple evacuation method. Using dry nitrogen affects the dehydration process by slowing it down because nitrogen is non-reactive and does not hold any moisture that could otherwise be introduced into the system.
Understanding Freeze Drying
Freeze drying is a dehydration process used to preserve food, in which low atmospheric pressure in a vacuum chamber accelerates water evaporation. This lowered pressure decreases the partial pressure of water, enhancing evaporation as those water molecules with high velocities leave first. The remaining molecules have a lover average kinetic energy, resulting in a drop in temperature and freezing of the food.