The influence of harvesting time and filtration on the quality of extra virgin olive oils extracted from Koroneiki olive fruits from higher altitude Messiniaki Mani

Abstract

Parameters playing an important role on the quality of olive oil include the olive fruits ripening stage (i.e. harvesting time) and filtration (i.e. stabilisation before storage). This study was aiming to investigate the influence of harvesting time (approximately 250 kg olives were collected five times in the period from the beginning of December until mid-February) and filtration on quality attributes of olive oils produced from Koroneiki drupes grown at higher altitude (400-450 m) in Exochori, Messiniaki Mani (Greece). The olive oil yield, defined here as kg of olives required to produce 1 kg of oil, decreased with increasing maturity index for the olives at later harvesting stages; i.e. the olive oil output increased by approximately 10-15%. All freshly pressed unfiltered and filtered samples could be classified as extra virgin olive oils (EVOOs), according to findings of acidity, peroxide and K values, and total phenols values of around 300 GAC/kg oil were observed for unfiltered samples (lower values were recorded for filtered samples). After 18 months of shelf storage in a cellar at 15 ± 5 °C the monitored acidity and K values increased but, with the exception of the K232 values, still stayed below the EU limit for EVOOs. However, higher acidity values were recorded for all unfiltered samples compared to the filtered samples at this stage. Accelerated oxidative stability tests showed an increase in peroxide values over time (up to 3.5 months at 60 °C) for all unfiltered samples and for filtered samples from the olives collected and pressed at the beginning and the end of the harvesting period. After these tests all samples, with the exception of the unfiltered sample from the end of the harvesting period, still displayed acidity values of below the 0.8% limit.