Whats the process for extracting vegetable oil?
Is it different for say canola oil than for soy or corn ?
When was vegetable oil first used? Did the ancient greeks use olive oil?
Corn, soya beans, castor beans, sunflower seeds, etc. are all products of vegetation and the oil is vegetable oil. The distinction is between oil from vegetation and that from minerals like petroleum (literally “rock oil”) and animal fats such as whale oil.
The traditional process is simply “pressing”. Virgin olive oil is the first pressing. Presumably non-virgin would be later pressings, with perhaps some higher tolerances for impurities. A more modern method of extraction is with chemical solvents such as hexane.