Partial De‐Stoning of Olive Paste to Increase Olive Oil Quality, Yield, and Sustainability of the Olive Oil Extraction Process

Abstract

Stone recovery in the olive oil extraction process can be an opportunity to increase both incomes and environmental sustainability. To this aim a new partial de-stoning machine (called Moliden) is installed at the first stage of an olive oil extraction plant to investigate its influence on the quality and sustainability of the extraction process. Quantitative and qualitative results are compared with those achieved using a conventional extraction process. Despite the 60% of stone recovered, no significant differences are registered for oil yield and extractability. A high-quality biomass is recovered by the partial de-stoner machine, belonging to A1 class quality when compared to the standard of the wood pellet, with the only exception of the moisture content. The partial de-stoning also improves the extra virgin olive oil (EVOO) quality in terms of hydrophilic phenols resulting in an enhancement of bitter and pungent sensory notes and most of all provides a beneficial effect for human health. Practical Applications: The new concept of partial de-stoner machine proposed in this work allows reducing the equipment employed in the extraction process of olive oil, since it consists of two sections: crushing and de-stoning. When compared with a standard unit, which recover pits from pomace, it provides a higher quality stone to be used as a biomass fuel. This leads to economic benefits for the millers and has a significant impact on the environmental sustainability of the process.

Experimental Investigation of a New Modular Crusher Machine Developed for Olive Oil Extraction Plants

“…The diameter of the holes and speed of rotation are also technological parameters to be considered during the crushing process, as they determine the thickness of the paste and thus the composition and quality of the final EVOO produced, as investigated by Inarejos-García et al [19]. These results are in accordance with those reported by other authors [14,17,21,22]. The present study entailed a set of experimental tests on a new machine, a new type of modular mechanical crusher developed in partnership with a private company manufacturing machines for the extraction of olive oil.…”

“…A higher granulometric fraction of KC olive paste entailed a lower level of POX activity during the mechanical extraction process, justifying the higher total phenol content of KC VOOs compared to HC VOO samples due to reduced oxidoreductase activity. The limited activity of POX, due to a mild disruption of the seed tissues or the use of a destoning machine, confirms results on the improvement of the phenolic compounds of VOOs during the mechanical extraction process [17,[37][38][39][40][41]. The new knife rotor, fitted with five overlapping fringes, was able to combine the optimal rupture of the olive pulp necessary for the biogeneration of phenolic compounds , limiting the negative effects due to the oxidation process induced by POX (Luaces et al, 2007;Garcia-Rodriguez et al, 2015) [35,37].…”

“…The crushing operation is crucial in determining the extraction yield, the quality and composition of the final product and the bioactivity level of the virgin olive oil produced [11,14]. Throughout this phase, all the endogenous enzymes of the olive fruit are activated and involved in subsequent phases in the extraction process, with them also being involved in the formation and modification of the phenolic and volatile compounds of the extra virgin olive oil (EVOO) [15][16][17]. The different mechanical aspects of crushers used in normal olive mills can result in different crushing effects, leading to different final concentrations in terms of phenolic and volatile compounds, which have significant effects on the taste, flavor and stability of the olive oil and thus the quality of the EVOO [18][19][20][21].…”

Effects of Ultrasound Technology on the Qualitative Properties of Italian Extra Virgin Olive Oil

“…The phenolic concentration of Canino, Coratina, and Peranzana showed an improvement of total phenols of EVOOs extracted from de-stoned olives compared to the control test, with significant increases of 21, 19.7, and 15.8%, respectively (Figure 6). The effect of the destoning process on phenolic content was not influenced by the genotypes, as reported by previous studies [26,29,40]. On the contrary, Criado-Navarro et al [41], in a recent study, showed a differentiated impact on secoiridoid content of Arbequina and Picual cultivars.…”

“…The values of the merchandising parameters did not show any significant alteration. The lack of effects on EVOO legal quality parameters has been confirmed by other authors, not only for the de-stoning process but also for new technologies with a high physicalchemical impact on the olive paste tissues [26][27][28][29]. The slight differences detected among the cultivars were not due to the different extraction processes but to the quality index and the different maturity of the olives.…”