HILIC-ESI-HRMS amino acid profiling of fruits of barattiere (Cucumis melo L.), a traditional Apulian melon landrace

Barattiere, an unripe Cucumis melo L. landrace from Apulia, Southern Italy, delights with its crisp texture, mild flavour, and exceptional digestibility, making it a cherished gem among vegetal food products. Yet, its biochemical secrets, especially the amino acid (AA) profile, that may underpin these traits, have remained largely hidden. To unlock them, we developed a green extraction using acidified water, optimized via design of experiments for up to 90% yields, and followed by analysis using hydrophilic interaction liquid chromatography-electrospray ionization high-resolution mass spectrometry (HILIC-ESI(+)-HRMS). This method separated all proteinogenic and non-proteinogenic (i.e., citrulline, ornithine, and GABA) AAs, including tricky isomers like Leu/Ile, in just 20 min. Profiling whole fruits and tissues (namely, epicarp/mesocarp vs. placenta) revealed striking differences across harvest years. Most abundant AAs included citrulline (33–250 µg/g fresh weight (FW)), glutamine (70–210 µg/g FW), and aspartic acid (11–160 µg/g FW). Total free AA concentrations ranged between 200 µg and 1 mg/g FW, often being larger than those found in other cucurbits, thus spotlighting barattiere’s nutraceutical value and supporting its valorization as a local landrace.