The authors demonstrated a meaningful decrease on all tested parameters with a marked reduction of riboflavin level (\(-30\%\)) in hazelnuts from the Akcakoca region of Turkey and of thiamine level (\(-50\%\)). Within the group of nutritionally relevant amino acids, lysine (Lys) diminished \(<\)\(-6\%\) in roasted Giresun hazelnuts but \(-31\%\) in Akcakoca hazelnuts. [PERSON] et al. [10] screened eighteen native hazelnut varieties from the Giresun province of Turkey for their sugars, organic acids, condensed tannins, and free phenolic acids profile. Fructose, glucose, sucrose, myo-inositol, raffinose, and stachyose ranged from \(1.99\) g/\(100\) g to \(4.94\) g/\(100\) g among the considered samples. Organic acids (oxalic, maleic, citric, malic, lactic, succinic, and acetic) ranged between \(0.96\) g/\(100\) g to \(2.72\) g/\(100\) g, while gallic acid was between \(0.159\) mg/\(100\) g and \(0.871\) mg/\(100\) g. The authors observed that roasting brought significant losses (\(p<0.05\)) of both condensed tannins (\(-97\%\)) and gallic acid (\(-67\%\)), whereas its effect on sugars and organic acids was not noteworthy. In a study aimed at evaluating the impact of different roasting conditions on phenolic compounds, [PERSON] et al. [11] revealed a marked decrease of all individual phenolics, with the exception of gallic acid while confirming the presence of flavan-3-ols (catechin, epicatechin, 2 procyanidin dimers, and 3 procyanidin trimers), flavonoids (quercetin pentoside, quercetin-3-O-rhannoside, and myricetin-3-O-rhannoside), hydrobenzoic acids (gallic acid, protocatechuic acid), and phloem-2\({}^{\prime}\)-O-glucoside (dihydrochalcone class). Nevertheless, the authors evidenced that roasting did not impact the total phenolic content (TPC) and antioxidative potential of kernels. These results are in accordance with those obtained by [PERSON] et al. [12], who monitored the TPC and antioxidant activity along shelf-life. The effects of roasting on proanthocyanidins were studied by [PERSON] et al. [13], who compared the content of extractable and bound proanthocyanidins of raw and roasted Turkish Tombul hazelnuts. In raw hazelnuts, extractable proanthocyanidins fraction was \(81\%\) of the total phenolic fraction with the presence of oligomers (4-9 mers) and polymers (\(\geq\)10 mers), whereas in roasted hazelnuts, extractable moieties were only monomers to trimers. This variation, likely related to skin loss during roasting, was accompanied by a higher recovery of dimers, trimers, and tetramers after alkaline hydrolysis of roasted hazelnut skins. [PERSON] et al. [14] focused on the lipid fraction and revealed just minor changes in fatty acid and triacylglycerol compositions. After intense roasting conditions (165-200 \({}^{\circ}\)C for 15 min on average), the authors observed a slight increase of oleic acid, saturated fatty acids, and triacylglycerions containing oleic acid moieties; and a decrease of linoleic acid, phytosterols (maximum 14.4%), and vitamin E homologues (maximum 10.0%). Negligible amounts of trans fatty acids also were detected. Of the studies focused on the effect of roasting in the development of characteristic brown color, [PERSON] et al. [15] evaluated the role of fat fraction, hexanal, and saccharose in color development and hydroxymethylfurfural (HMF) formation. HMF levels were highest in hazelnuts with the deepest browning; the lowest HMF and brown color were correlated to lower fat content (or defattted) samples. [PERSON] et al. correlated color and D- amino acids distribution, proposing a complex mathematical model (Back Propagation Neural Network on the Discrete Fourier Transform output of the whole surface color) to predict the occurrence of toxic compounds. The present study was designed to cover gaps for a more comprehensive understanding of the impact of roasting on the detectable metabolome of hazelnuts and on different hazelnut cultivars and harvest regions.