Keeping the oil in proper bulk storage conditions and packaging it on demand extends the shelf life of the oil compared to packaging it all at once. Our review (PDF 129 KB) of the scientific literature revealed that the type of packaging influences the oxidation rate of the oil. Dark or opaque packaging minimizes the light exposure that hastens oxidation.
To increase shelf life, oxygen in the container should also be limited, particularly in the headspace between the oil and the top of the package, although some headspace is necessary to allow for the natural expansion of the oil that occurs with increases in temperature. Some bottling equipment creates a vacuum in the package and/or injects inert gas into the package to eliminate oxygen in the headspace.
Bag-in-box packages, which include an inner bladder that collapses as the package is emptied, thereby keeping out air, have been shown to be superior for maintaining oil quality. Packages made of metal, such as tinplate, are desirable as they completely keep light out of the oil, as do coated-paperboard containers.
Dark glass has the desirable features of reducing light penetration and being nonpermeable, although there is some concern that oxygen enters the bottle through the cork or screw top. Clear glass exposes oil to light, but a label can be made to almost fully cover the bottle or the glass can be given a protective coating to keep out ultraviolet light—there is evidence that consumers like to see the oil when deciding what to buy.
Polyethylene terephthalate (PET) is the primary type of plastic used in olive oil packaging. PET has the advantages of low cost and recyclability, and a dark-colored PET reduces light degradation of the oil. However, PET is porous, which allows humidity and gases to enter the package.