Quality losses in virgin olive oil due to washing and short‐term storage before olive milling

To identify critical points during olive mill pre‐processing operations, the effect of the closed circuit washing stage on olive microbiological contamination, and the influence of the successive short‐term storage on olives and virgin olive oil (VOO) quality were evaluated. Microbiological, physical, and chemical parameters were assessed in olives and oils at three mill pre‐processing stages: reception, washing, and short‐term storage. Olive washing in closed loop systems was shown to be a critical control point at the olive mill due to microbiological cross‐contamination and fruit physical damage. Moreover, when the olives were short‐term stored before oil extraction, positive VOO sensory attributes decreased by as much as one point of intensity, as justified by the changes observed in phenolic and lipoxygenase derived volatile compounds. These results confirm the high risk of fruit cross‐contamination due to the poor hygiene of the water used in olives mills to wash olives, and point out the effect on VOO quality of a common practice such as short term silo storage of olives. Practical applications: The identification of new critical control points within pre‐processing operations in ordinary usage, and commonly accepted as good production practices, will contribute to enhance virgin olive oil quality. Preventive actions can be undertaken on the basis of the reported results, such as the control of water hygiene and short term storage conditions. The figure shows the microbiological contamination of olives during washing with recycled water and during short‐term silo storage, and the loss of sensory quality in the correspondent virgin olive oils.