Tin cans offer complete impenetrability to light and oxygen, preventing the reaction of photosensitive oxidation, catalyzed by the substance chlorophyll that is basically responsible for the deterioration of the quality of packaged olive oil. Since tinplate containers are impermeable to light, the complete removal of oxygen is not required in the packaging procedure, because the unsaturated fatty acids contained in the oil -especially the monounsaturated oleic acid- are not particularly prone to autoxidation.
Conversely, plastic and glass bottles, because of the transparency of the packaging, need to be sealed under vacuum to remove all air from the interior. Tin cans combine the best features of the two other alternative packaging materials and, in particular, the light weight and strength of the plastic with the complete sealing of the glass. This means that the oil packaged in tin cans preserves its high biological value till the last drop, even if the casually closed container remains in a kitchen cupboard for long periods of time.