Olive fruit fly effects on free acidity and peroxides value of olive oil

A field study was conducted on the effects of damage due to the infestation of the Bactrocera oleae (Rossi) on free acidity and peroxides value of olive oil. Olive fruits were harvested from field-grown, irrigated trees (Olea europaea L. 'Frantoio') at three dates in 2007. Samples were prepared so to obtain four (0, 30, 60, 100%) or five (0, 20, 40, 60, 100%) treatments of olive fruits, differing in percentage of olive fly exit holes. The fruits were either crushed using a miniature press or a laboratory-type mill and the oil was separated by centrifugation. The free acidity of the oil was generally low regardless of treatment at both dates, with values well below the limits for the extra-virgin oil category. Increases in free acidity and peroxides value of oils extracted on October 16 were apparent for the 60 and 100% treatments, but not on October 30. In the second experiment free acidity and peroxides value appeared directly related to the percentage of exit holes immediately after the oil was extracted