The interest in the phenolic compounds of olive oil is constantly growing, owing to their multiple functions, antioxidant properties, nutraceutical properties, the high stability that they provide to olive oil during storage and sensory characteristics ^[1][2]. Numerous studies (Table 1) have been conducted to clarify the relationship between destoning technology and the content of virgin olive oil phenolic compounds.

^21] observed that volatile components deriving from the lipoxygenase pathway were very influenced by the destoned process. In fact, volatile compounds of destoned oils from Coratina cv manifested a higher amount of C6 metabolites than those obtained with the traditional method. The sum of all C6 compounds, expressed as ppm, was 54.4 and 33.7 in destoned and whole samples, respectively. In particular, trans-2-hexenal was the main metabolite accumulated (44.8 and 30.7 ppm in destoned and whole samples). The authors concluded that the larger amount of C6 constituents in destoned oils would be related to a higher release of the membrane enzymes involved in the LOX pathway, due to effective grinding of the pulp tissues. In Coratina cv, Amirante, Clodoveo, Dugo, Leone and Tamborrino ^[5] reported an investigation on the volatile components of destoned oils in comparison with the oil from whole olives. Experimental data highlighted that the oils from destoning a greater quantity of C5 and C6 formed and were characterized by the presence of intense flavor notes in confront to these from the whole paste. Especially, trans-2-hexenal (185.4 vs. 110.8 mg/Kg in destoned and whole samples, respectively) and cis-3-hexen-1-ol (4.8 vs. 8.6 mg/Kg in destoned and whole samples). Servili et al. ^[8] investigated how destoning influenced volatile components in Frantoio and Coratina oils. The results indicated the C6 aldehydes quantity, such as trans-2-hexenal was higher in the crushed pulp, while C6 alcohols were greater in the seed. The trial demonstrated that the LOX pathway embroils diverse enzymes in various parts of the drupe. In fact, the seed showed a shorter hydroperoxide lyase and a greater alcohol dehydrogenase activity, in comparison to the mesocarp. These findings were in accordance with Luaces, Pérez and Sanz ^[22]. Moreover, C6 aldehydes amounts were higher also for destoned samples, whereas in the oils from whole olives the level of C6 alcohols was higher. The consequence of this feature is that the C6 unsaturated aldehydes positively enhance the cut grass notes of olive oil. Destoned oils from Gentile di Chieti, Caroleo and Coratina cv were compared with those obtained from whole olives ^[9]. The sample from stone removal showed greater amounts of volatile compounds, such as green aromas C6 aldehydes, alcohols, esters, and C5 compounds. Moreover, of great interest was the discovery of α-copaene and α-muurulene volatile components in destoned samples, in agreement with Saitta et al. ^[23]. Runcio, Sorgonà, Mincione, Santacaterina and Poiana ^[24] analyzed the influence of stone removal on volatile compounds in Carolea and Ottobratica oils. Data indicated that the destoned oils by the two morphologic different varieties had a greater content of C5 and C6, in comparison to whole oils, demonstrating that this characteristic was variety independent. In particular, the sum of the C6 compounds in Carolaea cv was 27.00 vs. 15.09 mg/Kg for destoned and whole samples, while in Ottobratica cv, it was 14.87 vs. 4.24 for destoned and whole samples, respectively. Composition of volatile fraction in destoned and whole Nocellara del Belice cv olives was reported by Ranalli and Contento ^[10]. Results suggested that destoning samples had higher concentrations of C5 and C6 volatile, responsible for the pleasant aromatic green notes in the oil. Unsaturated aldehydes were major metabolites, especially trans-2-hexenal was 425.1 vs. 331.2 mg/Kg in destoned and whole samples, respectively. This positive effect has been attributed by the authors to the milder functioning with small amounts of thermal energy, so as not to interrupt the hydro-peroxidelyase enzyme. Ranalli et al. ^[14] reported the differences of volatile composition in Olivastra di Seggiano oil obtained by destoning and traditional process. Stone removal from the fruit before processing displayed higher levels of C6 green volatiles, such as trans-2-hexenal (963.1 vs. 658.9 mg/Kg in destoned and whole samples, respectively). Moreover, in the destoned oil, the presence of new volatile molecules, α-copaene and α-muurulene, not present in the oil extracted from whole olives, was confirmed. More recently, Manganiello et al. ^[18] also found a growth in the total aldehydes, especially of the trans-2-hexenal for destoned oils in comparison with oils from traditional methods. The oils from Canino, Coratina, and Peranzana showed a different increment in aldehydes (33.4%, 19.4%, and 13.8%, respectively). Overall, an improvement in the quality of the pitted oils was confirmed also due to the increase in the volatile component. Several kinds of research on the influences of destoning technology on virgin olive oil volatile compounds are summed in Table 2.

Servili et al. ^[2] highlighted the importance of phenolic constituents due to their role against the oxidation of compounds present in oils. In the paper are discussed the mechanical technologies that influence their amount in the olive oil. Among these, mechanical extraction from destoned pastes has improved the phenolic content of the oils. Total phenols (mg/Kg) of virgin olive oils obtained from destoned and control (whole fruit) pastes were evaluated at time 0 and after 12 months of storage at room temperature (25 °C). Oils of destoned olive pastes had a content of 355 at the time 0 and 195 mg/Kg after 12 months, vs. oils of whole fruit olive pastes, with values of 345 at the time 0 and 150 mg/Kg after 12 months. The destoning process consented in part to removing peroxidase activity during the extraction process, improving the phenolic compounds of oils and their oxidative stability. Lavelli and Bondesan ^[3] studied the influence of destoning on the content in secoiridoids and the antioxidant activity of oils obtained from the Leccino, Moraiolo, Frantoio, Pendolino, Taggiasca, and Colombaia cultivars. Results showed that destoning has grown the secoiridoids and the antioxidant activity of oils (up to 3.5 times). Extra virgin olive, from destoned olives Leccino cv, had high phenolic content (1241 vs. 429 mg/Kg for destoned and stoned samples respectively). Destoning caused a minor increase in the phenolic content of Moraiolo cv (respectively 1072 vs. 1115 mg/Kg for the destoned and stoned samples). So, the study also indicated that these effects depended on variety, assuming that the influence of stone removal was associated with endogenous enzymes. Mulinacci et al. ^[4] focused on comparing the phenolic compounds of 16 fresh commercial samples of extra virgin olive oil obtained from both stoned and traditional methods. In the oils from destoned olives, higher concentrations of phenolic compounds were found in agreement with their higher antioxidant capacity. Among investigated cv, Coratina showed values of 120 vs. 52.4 mg/L for 3,4-DHEA-EDA in oils obtained from stoned and whole fruits respectively. Peranzana cv showed values of 169.8 vs. 114.4 mg/L for 3,4-DHPEA-EDA in stoned and traditional samples respectively. Del Caro, Vacca, Poiana, Fenu and Piga ^[6] evaluated the impact of the destoning method on minor components and antioxidants in oils from Bosana cv. In the destoned oils was found higher shelf-life with respect to these obtained from traditional systems. Luaces, Romero, Gutierrez, Sanz and Perez ^[7] assessed whether olive seeds played a role in the phenols of olive oils. The results showed an increase in total phenols in stone removal samples produced by Spanish cultivars (Manzanilla, Hojiblanca and Picual). The authors indicated that olive seeds carry the major peroxidase activity (72.4 U g (−1) FW), responsible for the degradation of phenols. Therefore, olive seeds are fundamental in determining the phenolic profile associated with their high peroxidase activity. The increase in total phenols was noted to be superior in Picual (34%) with respect to in Manzanilla and Hojiblanca (18%). Servili et al. ^[8] observed in the oils from destoned olives a notable increase of the phenolic heritage, particularly the secoiridoid derivatives such as the dialdehydic forms of elenolic acid linked to (3,4-dihydroxyphenyl) ethanol and (phydroxyphenyl)ethanol (3,4-DHPEA-EDA and p-HPEA-EDA, respectively) and the isomer of the oleuropein aglycon (3,4-DHPEA-EA) while the lignans have not undergone any changes. The stone removal process affects especially phenolic composition in Coratina cv, the secoiridoid derivates such as 3,4-DHPEA-EDA shows significant modifications (365.2 mg/Kg in traditional and 507.1 mg/Kg in destoned oils). Ranalli et al. ^[9] evaluated the oils obtained from destoned olives (Gentile di Chieti, Caroleo, and Coratina cultivars) compared to those with traditional extraction. The destoning has made it possible to obtain highly nutraceutical oils, with a higher content of hydrophilic biophenols. Coratina cv showed the highest content of secoiridoids (56 vs. 44 mg/Kg in the destoned and traditional samples, respectively); Caroleo cv showed 39 vs. 28 mg/Kg in the destoned and traditional samples, and Gentile di Chieti cv had 56 vs. 44 mg/Kg in the destoned and traditional samples. Ranalli and Contento ^[10] evidenced the effect of the destoning technique on the concentration of bioactive compounds. They found significantly increased content in oxidized oleuropein and ligstruside derivates in two oils obtained by Leccino cv, destoned vs. stoned. In particular, oleuropein aglycon, dialdehydic form (9.2 vs. 4.3 mg/Kg in destoned and stoned samples respectively), and ligstroside aglycon, dialdehydic form (24.1 vs. 10.0 mg/Kg in destoned and stoned samples respectively). This increase has been attributed to the removal of the stone rich in polyphenoloxidase enzyme, which is the principal cause of phenols’ oxidative phenomena in the oils. Hence, the destoning technique ensures a higher concentration of biophenols, and also richer quantity in α- and γ-tocopherol and in α- and γ-tocotrienol, entertained as important substances having a biological effect. Discrepancies among data concentration of total tocopherols after destoning have been reported. An increase of 4–27% in the findings of some authors ^[6][17] and a 1–12% decrease for other ones ^[3][11][13] were reported. Amirante, Clodoveo, Dugo, Leone and Tamborrino ^[5] considered the characteristics of Coratina cv oils both from destoned and in whole olives. This research confirmed that the destoning process determined higher total phenols in olive oils obtained. Phenolic content was 399 mg/kg in the oils obtained from destoned olive pastes and 235 mg/Kg in those from the traditional techniques. Analogous findings were also obtained by Gambacorta et al. ^[11]. In their research, the total phenols in oils from Coratina cv were found to be higher in destoned samples (450.7 mg/Kg), versus those from whole olives (338 mg/Kg). Concerning the phenol compounds, a significant difference was highlighted mainly for hydroxytyrosol and, also in this study, stone removal produced samples rich in phenols in comparison to these obtained from the traditional process (3.28 vs. 1.65 mg/Kg in destoned and whole oils respectively), (+)-1-acetoxypinoresinol (10.55 vs. 8.43 mg/Kg in destoned and whole oils respectively), and 3,4-DHPEA-EA (10.02 vs. 7.49 mg/Kg in destoned and whole oils respectively). Restuccia et al. ^[12] conducted an investigation into the influence of destoning on the antioxidant properties of extra virgin olive oil from Cerasuola cv. The comparison of the total phenolic content of the destoned and whole samples confirmed an increase in oils from destoned pastes. The amounts were 2.65 and 1.53 μmol GA/g polar extract for fractions from destoned and non-destoned respectively. Yorulmaz, Tekin and Turan ^[13] analyzed the effect of stone removal with malaxation in nitrogen atmosphere on the defense to oxidation of oils from Edremit yaglik cv. Findings demonstrated the oils destonated and malaxed in nitrogen flush had a higher total phenols content than those obtained with the same conditions but not destoned (328 vs. 282 mg/Kg respectively). Using destoning and malaxation together in the nitrogen atmosphere also increased the oxidative stability of oils (59.50 vs. 37.70% for samples malaxed under nitrogen flush destoned and non-destoned). Moreover, the authors highlighted that while destoning alone led to a 6% decrease in tocopherol concentration, adding nitrogen washing induced a 16% increase. Ranalli et al. ^[14] observed phenolic constituents in destoned (vs. whole) virgin olive oil from Olivastra di Seggiano cv. The authors investigated from 2008 to 2010 and showed an increase in the biophenols due to the destoning process by obtaining oils of elevated quality. They considered this fact probably due to the lower thermoquinonization of the phenolic molecules and the lower activities of oxidoreductase, present in greater quantities in the stone. Total ligstroside derivatives were 98.92 vs. 83.51 mg/Kg tyrosol for destoned and whole samples respectively. Destoned oils had also higher oleocanthal levels, p-HPEA-EDA, compared to whole olive samples (23 vs. 21.4 mg/Kg tyrosol). Katsoyannos et al. ^[15] investigated the effects of stone removal with different varieties (Greek varieties Koroneiki and Megaritiki) on the phenols of oils. The phenols of oils from destoned pastes were greater with respect to these obtained by the traditional method. Moreover, the total phenol content of Koroneiki from destoned samples (303.45 vs. 226.49 mg/Kg in destoned samples and whole samples respectively) was found to be significantly greater than that in Megaritiki pitted olive oils (258.05 vs. 222.99 mg/Kg in destoned samples and whole samples respectively). It was concluded that the pitting technique maintains high content of bioactive compounds. These results were recently confirmed by Criado-Navarro et al. ^[16], who evaluated the effects of stone removal before processing on the bioactive constituents in virgin olive oil. In their work, they analyzed “Arbequina” and “Picual” cultivars. Destoning has been demonstrated to have different effects for cultivars and especially on secoiridoid derivatives. It was observed that these compounds in “Arbequina” oil were present in minor quantities if stone removal was conducted, while an increase was observed in “Picual” oil obtained from destoned fruits. Thus, the metabolism of secoiridoids particularly β-glucosidases and esterases resulted conditioned by the destoning of olives in a significant way. Enlightenment for this fact would be that “Arbequina” oils from destoned olives had lost enzymes which are contained in the stone. The opposite consequence was revealed for flavonoids; in fact their concentration was enhanced in “Arbequina” oil from stone removal whereas in “Picual” flavonoids decreased in virgin olive oil from destoned olives. The authors established a direct incidence on the healthful effect bonded to the phenols; stone removal contributed to decreasing the health benefits of olive oil “Arbequina” while not “Picual” cv. These findings were confirmed by other studies ^[18] that observed destoned olives showed an improvement of extra virgin olive oil quality both for phenolic and volatile composition with a significant enhancement of sensory characteristics. The authors reported the influence of ultrasound technologies on the quality parameters and sensory profile of extra virgin olive oils extracted from whole and destoned olives of the three main Italian cultivars. In the studied cultivars, Canino, Coratina, and Peranzana there was an improvement of total phenols of oils extracted from destoned olives compared to the control test, with significant increases of 21, 19.7, and 15.8%, respectively. In this regard, it was highlighted that the destoning process increased oleuropein and ligstroside derivatives. The application of ultrasound coupled with the destoning process produced a slight enhancement of phenolic concentration.

Volatiles are very important compounds due to their impact on the flavor and sensory characteristics of oils. Many factors influence the volatile components such as cultivar, ripeness, geographic, and technological factors ^[19]. However, a significant proportion of the volatiles derives the enzyme activity lipoxygenase, especially during crushing and malaxation ^[20]. Angerosa, Basti, Vito and Lanza ^[

Sensory traits of extra virgin olive oil depend primarily on the phenolic heritage of olive cultivars and then on many other parameters, such as technological process. As highlighted by many authors ^{[2][3][4][5][8][9][10][11]}, the stone removal modifies the phenolic concentration in virgin olive oil, and consequently, also influences the sensory notes. Sensory analysis of destoned oils from Gentile di Chieti, Caroleo and Coratina cultivars was conducted, in comparison with the oils produced with the traditional process ^[9]. Data reported destoned oils had a delicate and harmonic flavor, characterized by marked green fruitiness, with respect to the oils obtained from the traditional system. Moreover, these positive sensory notes had scored higher by panelists (Coratina cv oils obtained a sensory scoring of 8.1 vs. 7.6 in destoned and traditional samples, respectively). The stoned oils had no marked bitter and astringent notes. This fact is favorable particularly for Coratina cv oils since it is a variety distinguished for the high intensity of bitterness and pungency. These results were in accordance with Gambacorta et al. ^[11]. They compared stoned and whole Coratina oils by evaluating the sensorial analysis. Samples obtained with the traditional process showed high notes in bitterness and pungency in comparison to destoned oils. Destoned oils, which had a malaxation presented a greater sensorial appreciation since they are very equable and fruity oils. Ranalli and Contento ^[10] confirmed that oils obtained from destoning technique were scored more by the panelists, and had a higher fruitiness, in comparison with whole olive oils. Ranalli et al. ^[14] reported the sensory characteristics of Olivastra di Seggiano oil from destoned olives compared to those from the traditional process. The sensory profile of the oil showed that among the sensory attributes, the artichoke taste was the most evident, and in the destoned samples, this sensorial attribute was higher compared to control (the median values of the artichoke attribute were 5.7 vs. 5.0 in destoned and whole oils respectively). In destoned oils, also the fruitiness flavor was more than the whole oils (the median values of the fruitiness were 8.6 vs. 7.0 in destoned and whole oils, respectively). Guermazi, Ghasallaoui, Perri, Gabsi and Benincasa ^[25] evaluated the sensory characteristic of oil produced from the whole and stoned olives of Chemlali cultivar, using the IOOC standard profile sheet method ^[26]. Results showed that the fruity positive attribute in conventional oil presented the lower values (2.6) while in destoned oils was almost double (5.1). For the pungent note, it was noted that the values had the same trend, they were respectively 5.7 and 2.3 in stoned and conventional oils. The stoned samples had lower values (2.1) for the bitter attribute in comparison with the conventional oils (5.7). So, the stone removal process increased the fruity and the pungent attributes, whereas it decreased oil bitterness. This fact improved the sensory quality of olive oil. In recent work ^[27], a partial destoning and a whole process were confronted to evaluate olive oil quality and its sensory characteristics. Data showed that the positive attributes (fruitiness, bitter and pungent) in Coratina cv oils obtained from partial destoned and whole olives were different. Particularly, the partial destoned oil had the fruitiness attribute higher than oils from whole olives (fruity was 3.9 vs. 2.5 respectively). Furthermore, green fruitiness and green almond were present in the partial destoned oil, while the whole oil had ripe fruitiness and ripe almond. Overall, the partial destoned samples were more harmonic in comparison with those produced using the traditional process, and for this reason, they were in better acceptance by consumers. Manganiello et al. ^[18] analyzed sensorial profiles of Peranzana, Coratina, and Canino cultivars highlighting that only for the Coratina cultivar, the destoning coupled with ultrasound treatment has decreased in bitterness and increased in herb sensation. In this regard, the increase in the “green” sensation contributed to enhancing the positive notes of the oil taste and the higher quantity of phenolic and volatile compounds due to the removal of the seeds, have given oil a greater sensorial score.