Here is what the home office said about the Young Living Distilling Process and all that our oils go through before reaching you at home:
I'd like to take a minute, and explain the process that we go through to insure the highest quality distillation possible. There is no other company, in the world, who goes to such efforts as we do in this area.
We completely clean the distilleries between plants such as balsam and lavender so we don’t have contamination of aromatic molecules from one plant type to another.
Because the spruce, pine, and balsam are all conifers and these oils have many of the same compounds, we do not have to clean the same way. All we have to do is steam and wash for four hours.
However, when we change from balsam to melissa , we fill the cooker with two feet of water and some soap and then steam for four hours which cleans the condenser and the separator and removes all the waxy substance that sticks to the walls. Then we rinse with hot water and two gallons of alcohol until all residue is gone. Then we close and put the steam through the system for six hours, completely and naturally sanitizing the entire system.
Next, we open the condenser and take the tube cleaning rod and clean each tube individually while steaming. The separator is then steam cleaned with the portable steam cleaner and then the final rinse cycle runs for another four hours. At that point, there is not any residue left. Again, no one else in the entire essential oil industry, other than Young Living, goes to this extreme level of effort.
After this lengthy cleaning we can then prepare for the next distillation. If we are going to distill melissa, the day we start, we put in enough melissa plant material to fill ¼ of the cooker. Then we distill this small amount which prepares the cooker, condenser, and separator. This oil is used to make the formula for our pesticide spray so it is not wasted. The oil is also tested and tests absolutely pure and is my guarantee of the quality.
We appreciate your asking about the "different" smell in the peppermint. It gives us the opportunity to let you know about the extraordinary effort by Young Living to provide the highest quality essential oils in the world.