The effect of different processing systems on the olive oil quality parameters of peroxide value and extinction coefficients K-232 and K-270 was studied. Olive oil was extracted by the traditional system of Theocharis, the centrifugal systems Alfa-Laval and Amenduni and the mixed type Rapanelli Sinolea and Decanter systems. The oil samples were analyzed initially and during storage in polyethylene bottles in the dark, diffused light and direct sunlight. Samples stored in the dark had significantly lower peroxide value. In general, the process of oxidation was slow in darkness and faster in diffused and direct light.