Rancid - defect
Rancid is one of the most common defects that can be found in an Olive Oil. The smell is that of oxidized fat left in the air. For some it can be traced back to the smell that you smell when opening a packet of old or expired chips.
It is a defect of the Oil that undergoes an oxidative process in contact with the air, and can be due both to the olive processing process, and to the natural deterioration of the product over time. For this reason it is necessary to store the product away from oxygen, light and heat sources.