# Filtration Scheduling: Quality Changes in Freshly Produced Virgin Olive Oil
## 4 Conclusions  
The focus of this original study was to optimise the scheduling of filtration during the olive milling season. Consequently, during the first month of storage, we examined the kinetics of volatile compound contents in immediately filtered olive oil samples and in the respective veiled olive oil samples, which would be hypothetically filtered after several days. Two effects were observed on the olive oil quality. First, the veiled oil samples were downgraded from the \"extra virgin\" to \"virgin\" quality category after less than five days in protective storage conditions. This deterioration was caused by the formation of unpleasant volatile compounds and an increasing perception of the \"fusty\" defect during storage, probably due to undesirable oil-born microorganisms. Second, lipoxygenase volatile compound contents were highest in the veiled olive oil samples, and the positive fruity sensory attribute was most marked in the veiled olive oil samples at the beginning of storage. It is possible that the appearance of the \"fusty\" defect could have masked an increase in the fruity attribute observed at the beginning of storage. Our experiment showed that a fast filter press filtration prevented microbial contamination and limited microbial and enzymatic activity. Consequently, the filtered olive oils samples were not downgraded, as the \"fusty\" defect did not develop; this critical, positive result outweighs the disadvantage of a less fruity olive oil. Figure 5: Mean contents of the volatile compounds related to the rancid defect in veiled (blue squares) and filtered (red circles) olive oil samples during storage. The obtained results allowed to increase the general knowledge of the volatile compositions of filtered and unfiltered olive oils during the first month of storage and to confirm the stabilisation role of filtration due the removal of water, solids, and microorganisms, limiting the microbial and enzymatic activity. Indeed, the microbial and endogenous enzyme activity, responsible for the development of volatile compounds related to defects like \"fusty\" and \"muddy\", were promoted by factors such as the oil turbidity, water and solid contents, and high water activity. The comparison between the kinetics of the volatile compound contents in the veiled and filtered olive oil samples has shown not only that unfiltered oils deteriorate more than filtered ones but, also, that this deterioration is really fast. The innovative take by this work is an operative contribution to optimise the workload during olive oil production. Our study demonstrates that filtration should be carried out within a few days after olive oil production to reduce the risk of the emergence of sensory defects. Furthermore, a trade-off between workload and quality risk was highlighted. Immediately after the production, the workload is at its peak, while the risk for quality is minimum. Then, the workload progressively decreases, while the risk increases until the commercial category downgrade. According to our data, the filtration had to be done in five days from the production. This value could change according to the turbidity composition of the olive oil, but only in the first few days did we find a low risk for extra virgin olive oil quality. Conceptualisation: L.G. and A.P. ; funding acquisition: L.G., B.Z., and A.P. ; investigation: [PERSON], L.C., G.A., and P.M.; project administration: L.C. ; supervision: [PERSON] and A.P. ; writing--original draft: [PERSON] and C.B. ; and writing--review and editing: [PERSON] and B.Z. All authors have read and agreed to the published version of the manuscript. This research was funded by Monini S.p.A. The authors would like to particularly thank [PERSON], [PERSON], and [PERSON] for their support during the experiment. Moreover, the authors would like to thank [PERSON] of Fattoria Altomena S.r.l. for his support during crop season. The authors declare no conflicts of interest.