Nosespace analysis by PTR-ToF-MS for the extravirgin olive oil characterization

Introduction: Extravirgin olive (EVO) oil aroma and taste influence consumer preferences. Volatile organic compounds (VOCs) release from food within oral cavity is a complex process. Nose-space (NS) analysis should unravel the retro-nasal olfaction processes happened during olive oil tasting. Proton Transfer Reaction-Mass Spectrometry with Time-of-Flight analyser (PTR-ToF-MS) was already successfully applied for NS analysis of apples [2], cereal bars [3], coffee [4,5]. Methods: In this study 2 Italian EVO oils were used: commercial vs home made (Lago di Garda, TN). Pure oil, oil mixed with tomato sauce, oil on bread prepared for each EVO oil were used for headspace (HS) and NS measurements by PTR-ToF-MS 8000. The samples were presented to 8 assessors in duplicate. For NS sampling a glass nose-piece with silicone rubber tube was fitted into assessors’ nostrils and connected to PTR-ToF-MS. The method for HS analysis was described elsewhere [6]. Results: 26 out of 319 mass peaks of NS dataset displayed signal related to olive oil, tomato or bread aroma. Peaks related to human metabolism were eliminated. The individual profiles differed in peak intensity and duration. However it was possible to distinguish the two types of EVO oils. HS data confirmed diversity of the oils. Home-made EVO oil in all products was characterized by significantly higher concentrations of mass peak 99.081 tentatively identified (t.i.) as (E)-2-hexenal associated to a green-leaf and fruity flavor [1]. Commercial EVO oil was richer in t.i. pentanal, acetic acid, butanal, and several esters which are reported as oxidation products of olive oil [7]. The samples of olive oil on bread showed the best performance (higher signals intensities) for all panellists due to an increased release surface area, prolonged presence in mouth, increased interaction with saliva and mucosal surfaces. Adding tomato sauce to olive oil decreased the olive oil aroma release in NS and contaminated it with tomato aroma. Conclusions NS analysis performed by PTR-ToF-MS discriminated different EVO olive oils. HS and NS data were consistent. The next steps are the optimization of sample preparations, tasting protocol, and the improvement of PTR-ToF-MS sensitivity by applying an ion funnel. The optimized methods will be applied to study different EVO olive oils within the project “VIOLIN” aiming to the valorisation and promotion of Italian EVO oils. Novel Aspect: For the first time NS analysis was applied for olive oil profiling taking into consideration individual perception and the combination with different food matrices.