Four commercial samples of extra-virgin olive oil have been analysed in order to evaluate the influence of storage time on quality. The following parameters were determined after 3 and 6 months of storage: acidity, peroxide index, absorption coefficients K270 and K230, percentage of humidity, impurity content (%), phenols content, iodine index, saponification index, colour index and fatty acid content. At the same time, the effects of container type on the deterioration in quality were studied. Each olive oil was stored in five different containers at room temperature with the same surface area of exposition to air and light: clear PET bottle, PET bottle (covered with Al foil), glass bottle, tin, and Tetra-brik®. The results showed a gradual loss of quality during storage, especially in plastic or glass bottles. The best containers for commercial packing of extra-olive oil were tin and Tetra-brik®.
