Pheophytin α degradation products as useful indices in the quality control of virgin olive oil

In previous studies we reported the presence of compounds with spectral characteristics similar to pheophytin a (Pheo alpha), which often accompany the Pheo a peak in the chromatographic profile of virgin olive oils (VOO) at 410 nm under normal-phase HPLC conditions. The occurrence and levels of these compounds were found to be affected by storage conditions of the oil samples. In the present study we investigated whether the major Pheo a degradation products, identified as pyropheophytin alpha (coeluting with the respective epimer) and 13(2)-OH-pheophytin alpha, could be used as estimates of VOO history. The content of Pheo a and its degradation products was determined for a great number of authentic olive oil samples of unknown history. Results are discussed in comparison with other quality indices (e.g., antioxidant content) when necessary. High amounts of the pyro form (20-30% of total pheophytins) were related to thermal abuse or lengthy storage. The presence of allomers indicated oxygen availability. The levels of these products, 0-20% of the total pheophytin content for 62% of the samples, seemed to be influenced by the presence of pro- and antioxidants. When low levels of Pheo a are not accompanied by other degradation products, light exposure for a certain period of storage can be assumed.