Advanced spectroscopic techniques to investigate on the primary metabolome of the Vallo di Diano onion and highlight diagnostic compositional and nutraceutical features

Powerful, innovative and alternative analytical methods are required to characterize in-deep food and develop tools to protect agrobiodiversity heritage, identify peculiar nutraceutical and nutritional features, and investigate on the adaptability to soil and climatic conditions. The San Pietro al Tanagro onion (SPT) is a native copper onion of Vallo Di Diano (Southern Italy, Salerno) which, despite its promising organoleptic qualities, has never been studied in-depth and characterized through modern and advanced analytical techniques. In line with the ob- jectives of the European commission, such an approach may help valorizing and protecting it, being an autochthonous species at risk of extinction. Therefore, we assessed important quali- and quantitative charac- teristics of representative SPT samples grown under different conditions (open field vs under greenhouse) and compared with those of a commercial “ Montoro copper onion ” , a well-known autochthonous Italian variety belonging to the same onion group and serving as external copper onion reference. Beyond nutraceutical ana- lyses, we exploited advanced high resolution 1H nuclear magnetic resonance (NMR) and Near infrared (NIR) spectroscopies to characterize the primary metabolome of studied onion samples and identify their molecular fingerprint via metabolomics (PCA, PLS-DA and Heat-Map clustering). We demonstrated that NMR and NIR data unveiled important molecular traits useful to enable a clear and significant discrimination among all examined onions samples. Our findings permit to candidate the proposed composite approach as an effective strategy to identify and trace high-quality onion production.