I’m back home from college and noticed that the vegetable oil that my parents use is stored in a container but the lid is missing. How long would it take for it to oxidize? Is it safe to consume oil that’s been exposed to the air for multiple months?
I would toss it. Oxygen can make the oil rancid and in all truth- opened cooking oil shouldn’t be used past 6 months anyways…or maybe less: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4245579/
I have no scientific knowledge regarding this, but anecdotally, my dad had a Fry Daddy with no lid that sat on his counter for years and got used 3-4 times per week (we Appalachians like deep frying) and it always tasted fine to me.