In an effort to avoid hosting a game of bear-bag pin~ata, and also as an excuse to learn something about chemistry, I'm curious about the odor barrier properties of PET soda bottles as an alternative to Opsak or the lighter plastic bags I've seen discussed in this forum. I've been reading about the properties of various plastics and PET seems to have even lower gas permeability than the plastic used in odor-proof bags such as Opsak. I've also been surprised that different plastics seem to have different permeability to different gasses: for example PET is very good at blocking CO2 (important for soda) but is not necessarily as good at blocking O2. I know that odor transmission is all about molecules but don't know which molecules are the important players in food smell and how they stack up against the various types of plastic.

My last two trips were short and I didn't cook. Almost all of my food consisted of peanuts, steel-cut oats, and sport drink mix, all of which could have been stored in soda bottles. My half-baked concept is that if all of the food is in bottles, and if some level of negative pressure could be applied inside the bottle before sealing (such as a squeeze before twisting the cap closed) then there will be very little molecular flow through the plastic and almost all of it will be directed inward. My engineer mind says that this should equate to little or no odor transmission.

Storing cooking utensils in a soda bottle might be problematic, so this concept is primarily aimed at no-cook trips.

Are there any chemists out there who would like to weigh in?

This not an attempt to justify ignoring bear canister or hanging advice: both of those primary food defense measures should benefit from even imperfect odor reduction.