Investigating hazelnut roasting with a multi-analytical technique approach

Hazelnut (Corylus avellana L.) is a tree nut with relevant industrial importance. 90% of hazelnut consumption is based on processed products obtained from roasted kernels, such as grain and paste, widely used as raw material for confectionery industry [1]. Therefore, roasting is a fundamental step in hazelnut industrial processing. The thermal treatment triggers microstructural modifications and chemical reactions, leading to changes in morpho-textural properties [2] and volatilome profile [3]. In this study, the roasting process was carried out in a pilot scale infrared roaster. Small aliquots (150200 g) of kernels were collected regularly throughout the thermal treatment, obtaining samples at increasing roasting intensity. Each aliquot was processed to obtain the paste samples, which were characterized for the morpho-textural properties (color and texture) and the profile of volatile organic compounds (VOCs). Hazelnuts from three different geographical and botanical origins were employed in this study: Tonda Gentile Romana monocultivar hazelnuts from Lazio region (Italy), Tonda Gentile delle Langhe monocultivar hazelnuts from Piemonte region (Italy), and Akçakoca hazelnuts from Turkey. The hazelnut paste VOC profile was determined by applying three analytical approaches, namely gas chromatography - ion mobility spectrometry (GC-IMS), proton transfer reaction – time of flight – mass spectrometry (PTR-ToF-MS) and gas chromatography – mass spectrometry (GC-MS). Outcomes of this study demonstrated the complementarity of these analytic techniques and the prospect to apply them to assess the evolution of hazelnut volatilome during roasting.