Investigation of Volatile Compounds in Two Raspberry Cultivars by Two Headspace Techniques: Solid-Phase Microextraction/Gas Chromatography-Mass Spectrometry (SPME/GC-MS) and Proton-Transfer Reaction-Mass Spectrometry (PTR-MS)

The volatile compounds emitted by two raspberry varieties (Rubus idaeus, cv. Polka and Tulameen) were analyzed, in both the case of fresh fruits and juices, by two headspace methods that are rapid, solvent-free, and with reduced or no sample pretreatment: solid-phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) and proton-transfer reaction-mass spectrometry (PTR-MS). Multivariate analysis of the SPME/GC-MS results allows for an unambiguous sample discrimination for both mashed fruits and juices. PTR-MS instrumental fingerprint provides, in a faster way, similar qualitative information on the overall flavor profile. The two cultivars show both qualitative and quantitative differences. SPME/GC-MS analysis shows that alcohols and aldehydes are more abundant in the headspace of Tulameen as, e.g., hexanal and hexanol that induce herbaceous odor notes. This observation has been confirmed by sensory analysis. PTR-MS was also used to monitor rapid processes that modify the original aromatic profile, such as lipo-oxigenase activity induced by tissue damages occurring during industrial transformation, accidental mechanical damages, or as a consequence of chewing.