Abstract
This study focuses on the detectable metabolome of high-quality raw hazelnuts (Corylus avellana L.) and on its changes after dry-roasting. Informative fingerprinting was obtained by comprehensive two-dimensional gas chromatography with fast-scanning quadrupole mass spectrometry (GC×GC-qMS) combined with dedicated data processing. In particular, combined untargeted and targeted (UT) fingerprinting, based on pattern recognition by template matching, is applied to chromatograms from raw and roasted samples of Tonda Gentile Trilobata and Anakliuri hazelnuts harvested in Italy and Georgia. Lab-scale roasting was designed to develop a desirable organoleptic profile matching industrial standards. Results, based on 430 peak features, reveal that phenotype expression is markedly correlated to cultivar and pedoclimatic conditions. Discriminant components between cultivars are amino acids (valine, alanine, glycine, and proline); organic acids (citric, aspartic, malic, gluconic, threonic, and 4-aminobutanoic acids); and sugars and polyols (maltose, xylulose, xylitol, turanose, mannitol, scyllo-inositol, and pinitol). Of these, alanine, glycine, and proline have a high informational role as precursors of 2-acetyl- and 2-propionylpyrroline, two key-aroma compounds of roasted hazelnuts. Roasting has a decisive impact on metabolite patterns—it caused a marked decrease (−90%) of alanine, proline, leucine and valine, and aspartic and pyroglutamic acid and a −50% reduction of saccharose and galactose.
Highlights
Roasting is a key technological step for hazelnut industrial transformation that yields distinctive flavors, color, and crunchy texture
2D peak patterns generated by comprehensive two-dimensional gas chromatography (GC×GC) can be considered as a sample’s distinctive fingerprint, and the detected compounds as minutiae features to be annotated and tracked across multiple samples
The term “minutiae” derives from biometric fingerprinting used in forensic science [50], therein indicating ridge endings and bifurcations on fingertips whose relative position is unique in each individual
Summary
Roasting is a key technological step for hazelnut industrial transformation that yields distinctive flavors, color, and crunchy texture. It triggers a complex array of many different chemical reactions, mainly involving major constituents—carbohydrates, proteins, free amino acids, and fats [1,2,3,4,5,6]. The high temperatures adopted during roasting impact the integrity of oleosomes (reserve bodies of lipids in raw hazelnuts) and reduce oxidative stability [7]. Lipid oxidation contributes to the formation of reactive carbonyl compounds (in particular, glyoxal and methylglyoxal). High-molecular-weight products characterized by a brown color (melanoidins) are formed, contributing to the final color of the product
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
