Application of on‐line HRGC‐FTIR spectroscopy to the analysis of acetylenic flavour precursors

Aroma extracts from various plants were screened for acetylenic flavour precursors using on‐line HRGC‐FTIR spectroscopy. Selected wavelength monitoring (2100–2250 cm−1) revealed for the first time the presence of 3‐hydroxy‐7,8‐didehydro‐β‐ionone in peelings of lulo syn. naranjilla (Solanum vestissimum D.) fruit. The same compound was also detected as a major aglycone after enzymatic hydrolysis of a glycosidic extract isolated from Vitis vinifera cv. Riesling leaves. The related acetylenic diol, 3‐hydroxy‐7,8‐didehydro‐β‐ionol, was similarly identified as the aglycone in a glycosidic extract obtained from purple passion fruit (Passiflora edulis Sims) juice. The discovery of these acetylenes is discussed with regard to the formation of β‐damascenone in plants.