Characterization of table olives from “Piantone di Mogliano” cultivar: proteomic studies and antioxidant properties evaluation

“Piantone di Mogliano” is an olive cultivar from Marche region, mainly located in Mogliano (Macerata). This work aimed to the production of table olives from “Piantone di Mogliano” through innovative techniques able to enhance both taste and nutritional properties of the olives. In general, olive drupe is composed by water, fat, carbohydrates, protein, fibre, pectin, biophenols, vitamins, organic acids and mineral elements which all together are responsible for the quality and aroma of the fruit. The quality of the table olive is also due to several factors including suitability of raw materials, nutritional composition and sensory properties and processing technologies. These latter are very important since olives are rarely used in their natural form due to their bitter taste. In this work, two processing technologies were used: the Sevillian style (Sst) and the Natural style (Nst.) In each final product, the total polyphenol content and the antioxidant activity was determined, furthermore, and all the values obtained were compared to that of the Raw Olives (RO) Finally, a proteomic characterization, until now only on the RO, has been carried out. “Piantone di Mogliano” olives were subjected to Sst (based on NaOH and partial fermentation) and Nst (based only on fermentation) processes, modified in order to obtain a final product with enhanced organoleptic characteristics. In the RO, Sst and Nst olives the polyphenol total content was determined according to the Folin-Ciocalteu method and the total antioxidant activity was assessed through the total antioxidant activity (TAA) test and the chemiluminescence assays [1, 2]. As a result, it was found that RO has a polyphenol content of 6,45 mgGAE/g, Nst keeps its phenolic composition almost unaltered (5,69 mgGAE/g), whereas the Sst have the lowest polyphenol content (2,93 mgGAE/g), if compared to RO. Chemiluminescence assay was performed using two specific probes, lucigenin and luminol, that are sensitive to superoxide anion and hydrogen peroxide, respectively. In all cases, the results indicated that the natural style olive extracts have an antioxidant activity similar to that of raw olive extracts. As regard to the total antioxidant activity evaluation, Nst has an antioxidant activity similar to RO and proved to possess a greater antioxidant activity with respect to Sst. Thanks to the proteomic studies, it is possible to achieve a sort of "identity card", very important for the traceability of “Piantone di Mogliano” olives. The protein extraction method, performed as previously described [3], removed the interfering substances (i.e. lipids) and allowed to obtain a concentrated protein fraction from the olive pulp (0.025 mg/g of olive powder). Two-dimensional electrophoresis (2DE), performed until now only on RO extracts as previously described [3], revealed the presence of some proteins with a particular biological interest such as thaumatin like-protein, a polypeptide with a molecular weight (MW) of 25.0 kDa involved in plant resistance mechanisms. Thaumatin-like proteins can be induced by a large spectrum of pests (such as viruses, bacteria, and fungi) and possess antibacterial and antifungal activity. Other proteins identified by 2DE were: copper and zinc superoxide dismutase (MW: 15.0 kDa) which catalyses the two-step dismutation of the toxic superoxide radical to molecular oxygen and hydrogen peroxide and exerts an important antioxidant defense in living cells exposed to oxygen; formin-like protein 4 (MW: 84.0 kDa), involved in the organization and polarity of the actin cytoskeleton; phospholipid-transporting ATPase 1-like (MW: 33.0 kDa). The results of this study proved that the Nst olives maintain their antioxidant power and total polyphenol content with respect to the Sst olives. Further proteomic studies are in progress in order to assess the protein profile of Sevillian and Natural style olives. References [1] Pellegrini N, Visioli F, Buratti S, Brighenti F. Direct Analysis of Total Antioxidant Activity of Olive Oil and Studies on the Influence of Heating. J Agric Food Chem. 2001; 49: 2532-2538. [2] Gabbianelli R, Santroni AM, Kantar A, Falcioni G. Superoxide anion handling by erythrocytes loaded with alpha and beta haemoglobin chains: a chemiluminescence study. In: Campbell AK, Kricka LJ, Sanley PE, Ed. Chichester, U.K.: John Wiley and Sons. 1994; 227-230. [3] Ariani A, Polidori P, Wang M, Pucciarelli S, Polzonetti V, Vincenzetti S. A proteomic approach for the characterization of olives from “Piantone di Mogliano” cultivar. 2° Convegno Alimenti e nutraceutici: qualità e salute del consumatore. 2017. ISBN: 978-88-6768-028-3. pp 43-44.