Elucidation of Endogenous Aroma Compounds in Tamarillo (Solanum betaceum) Using a Molecular Sensory Approach

Glycosidically bound volatiles (GBVs) are flavorless compounds in fruits and may undergo hydrolysis during fruit maturation, storage, and processing, releasing free aglycones that are odor active. However, the contribution of glycosidic aglycones to the sensory attributes of fruits remains unclear. Herein, the key odor-active aglycones in tamarillo fruits were elucidated through the molecular sensory approach. We extracted GBVs from three cultivars of tamarillo fruits using solid-phase extraction and subsequently prepared aglycone isolates by enzymatic hydrolysis of GBVs. Gas chromatography-mass spectrometry-olfactometry (GC-MS-O) coupled with odor activity value (OAV) calculation, comparative aroma extract dilution analysis (cAEDA), and omission tests were used to identify key aromatic aglycones. A total of 42 odorants were determined by GC-MS-O analysis. Among them, trans-2,cis-6-nonadienal, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF), linalool, 4-vinylguaiacol, geraniol, and α-terpineol showed high OAVs. The cultivar Amber had more aglycones with flavor dilution (FD) factors >16 than the Mulligan cultivar (27 vs 21, respectively), and the Laird's Large fruit showed the highest FD of 1024 for glycosidic DMHF. Omission tests indicated 14 aglycones as essential odorants related to GBVs in tamarillo fruits. Moreover, the enzymatic liberation of aglycones affected the sensory attributes of the tamarillo juice, resulting in an intensified odor profile with noticeable fruity and sweet notes. This study gives insights into the role of endogenous aroma during tamarillo-flavor perception, which lays the groundwork for developing tamarillo-based products with improved sensory properties.