Effect of facilitated harvesting and fruit cooling on extra virgin olive oil quality

To produce high quality olive oil, best practices recommend both to avoid fruit damages during the harvesting and to avoid long storage time between harvesting and crushing. The mechanical harvesting could damage the olives, favouring pulp softening, cell breakage, increasing the fruit respiration and leading to a fast olive oil degradation. Furthermore, the working capacity of the plants is not sufficient to cover the incoming volumes of olives, and a storage period is needed. To minimise the spoilage of olives, several hand-held facilitating machines were developed and refrigerated cells for fruit storage are currently spread. A full factorial design evaluated the combined effects of harvesting method (manual vs facilitated), storage temperature (25 degrees C vs 6.5 degrees C) and their interaction, aiming to understand if the storage at low temperature, applied to olives harvested using hand-held electric combs, could mitigate the potential negative effects given by the beating. From chemical analyses of legal parameters, phenolic and aromatic fractions, the highest amounts of total phenolic compounds occurred in olive oil samples, extracted from olives harvested through the manual method. Moreover, storage at low temperature preserved secoiridoids, even if it favoured their oxidation. The mechanical stress on olives due to harvest resulted in preferably activating the oxidative reactions, including the lipoxygenase pathway, which is responsible for the production of olive oil fruity notes. The latter phenomena were enhanced by low temperatures, probably due to the higher solubility of oxygen and the selected activity of hydroperoxide lyase.

Automated summary

To produce high quality olive oil, it is important to avoid fruit damages during harvesting and minimize storage time between harvesting and crushing. Mechanical harvesting can damage the olives and lead to fast degradation of olive oil. Hand-held facilitating machines and refrigerated fruit storage cells have been developed to minimize spoilage of olives. A factorial design study explored the combined effects of harvesting method, storage temperature, and their interaction. Results showed that manual harvesting and low temperature storage preserved the highest amounts of phenolic compounds in olive oil samples, but also facilitated their oxidation. Mechanical stress on olives during harvest activated oxidative reactions, particularly the lipoxygenase pathway responsible for fruity notes in olive oil. Low temperatures enhanced these reactions, possibly due to higher oxygen solubility and enzyme activity.