Decoding carob flavor aroma using HS-SPME-GC-MS and chemometrics

Ceratonia siliqua L. is quite popular for the sweetness of its fruit ("natural chocolate") and the strong, persistent, characteristic odor that associates not only carob fruit, but also its traditional food products. This is due to the emission of an array of volatile organic compounds (VOCs). The released odor is a complex mixture, and therefore, needs to be separated prior detected, especially when its origin varies and is engaged. Therefore, Headspace-Solid-Phase Microextraction-Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS) analysis was performed in ground carob pods from three different European countries to decode their released aroma. The method was applied to Cypriot (Kountourka, Koumpota, Tilliria), Spanish (Negra, Rojal, Matalafera) and Italian (Saccarata, Racemosa, Gibiliana) cultivars, and the released volatile species were further processed with multivariate data analysis (MDA). The chromatographic separation highlighted 54 common VOCs in the grounded carob pods; the most abundant appeared to be propanoic acid 2-methyl (isobutyric acid), acetic acid, butanoic acid, hexanoic acid, and propanoic acid 2-methyl-methyl ester. The quantitative results for acetic acid, propanoic acid 2-methyl, butanoic acid, furfural and pentanoic acid revealed their emission in the low ppb(v) levels. The engage of MDA on the obtained results showed a clear differentiation of the carobs based on their geographical and botanical origin. The combination of HS-SPME-GC-MS and chemometrics contributes to the quality characterization of carobs and highlights their authenticity markers.