Influence of decanter working parameters on the extra virgin olive oil quality

An experimental investigation was carried out in order to get more information about the influence of decanter processing parameters on the quality of the extracted extra virgin olive oil. In particular, both two- and three-phases decanter, set up at two different differential speeds between drum and cochlea (Dn16 and Dn11), were considered. The determinations of the free fatty acids, peroxide value, spectrophotometric constants, phenols, tocopherols, carotenoids, chlorophylls, and antioxidant activity were carried out on samples, as well as sensory and volatile compounds analyses. The obtained results showed that increasing the Dn, the oils obtained were more pungent and richer in aldehydes and antioxidant compounds; whereas the oils extracted at lower drum speeds were more bitter and showed higher peroxide and K270 values, as well as higher amounts of volatile compounds related to aldehydes oxidation. Moreover, the addition of water, made when working at three-phases, decreased significantly the level of phenolic compounds, but allowed to retain more tocopherols and carotenoids. On the other hand, the extraction with the three-phase decanter determined a more perceivable fruity note and higher levels of trans-2-hexenal, but only in the oils obtained at higher speeds. The oils obtained with the two-phase decanter were more pungent and richer of volatiles related to this sensory note. Practical application: The results of this paper help to understand the influence of decanter processing parameters (differential speeds between drum and cochlea, working at two and three-phases) on the quality of the extracted oil. Technical innovation in decanters would enable real-time adjustments of working parameters in function of the different raw material characteristics.