Chemicals with sweet aroma descriptors found in Portuguese wines from the Douro region: 2,6,6-Trimethylcyclohex-2-ene-1,4-dione and diacetyl

2,6,6-Trimethylcyclohex-2-ene-1,4-dione (TMCHD), a norisoprenoid with a swe et honey aroma descriptor, is reported for the first time as a minor consti tuent of single-varietal table and fortified wines from the demarcated Dour o region. Olfactory gas chromatography (GC-O) of a volatile wine extract, p reviously isolated by preparative gas chromatography, indicated the presenc e of a zone containing an intense honey descriptor. The targeted odor compo und was identified by GC-MS, GC-O, and Kovats index. Quantitative analysis using a selected characteristic ion (m/z 96) indicated that young Douro for tified wines from the 1997 vintage contained up to 4 mug/L TMCHD. The sweet honey sensory threshold limit for TMCHD in a model Port wine solution was found to be 25 mug/L. TMCHD is therefore only likely to contribute as a col lective element to Port wine aroma. The wine volatile diacetyl was identifi ed as a strong contributor to the sweet caramel aroma descriptor often asso ciated with Port.