UTILIZZO DELL'ANIDRIDE CARBONICA EMESSA DALLE PASTE DI OLIVA DURANTE LA TRASFORMAZIONE PER MIGLIORARE LA QUALITÀ DELL'OLIO. SECONDO CONTRIBUTO: PROVE DI FRANTOIO

Abstract - The aim of this work was to investigate the qualitative effects of an innovative malaxation technique for extra virgin olive oil extraction at industrial plant scale. This technique allows to reduce oxidation processes through the protection against oxygen by means of the natural CO2 emission of olive paste during malaxation. For this purpose a conventional (horizontal) malaxator was modified for working under confined atmosphere (hermetically sealed apparatus). Two malaxation trials were conducted, one with the sealed apparatus and another one with open-to-air in order to allow the free oxygen exchange (control). Chemical analyses such as total acidity, peroxide value, chlorophyll concentration and profile of hydrophilic phenols were used to assess the quality of the olive oil. The air in the head space of the sealed apparatus was sampled and analyzed. The variations of CO2 concentration, as a function of the time, resulted slower than those reported in analogous lab scale trials (oxygen concentration reaches the 50 % of the initial value after 50 min malaxation time). Therefore, the effectiveness of the protection against oxidations was limited. Nevertheless, the oils with the sealed malaxator, for each time of malaxation, showed a smaller values of peroxides and a larger content in total chlorophylls and hydrophilic phenols. The compound mainly affected by the treatment was DMO-da (dialdehydic open form of decarboxymethyl elenolic acid linked to 3,4-Dihydroxyphenylethanol), with a 30 % increase in concentration over the control. The sensory evaluation of olive oils did not show any negative attributes due to the treatment, while the intensities of bitterness and pungency perceived by the testers were potentially higher for oils from the sealed malaxator than the open-to-air apparatus.