The oil of the olive fruit, obtained by pressing the fruit at various stages of maturity. About 70 - 90% of the liquid obtained from olives is bitter water residue, which must be extracted to produce oil. Oil is classified as extra virgin or virgin according to its chemical makeup (the amount of acidity in the oil). Pure olive oil or light olive oil come from secondary pressings or are obtained from re-processing olive mash. The ideal shelf life of olive oil is about one year and it should be kept in a cool, dark place away from direct sunlight.