system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are plastic chip bags always chrome on the inside?
gpt
Chip bags are usually given an interior coating of aluminum. This is because most bags are made of polyethylene, which is not an oxygen barrier. As the oils in the chips oxidize, the flavor changes (they basically sour), which would severely shorten their shelf life. In order to slow this process, the plastic is doped (coated) with a very thin layer of aluminum to help block oxygen. The bags are also usually packed in a nitrogen or other inert-gas environment to further delay oxidation.