Sensory threshold of 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) and concentrations in young Riesling and non-Riesling wines.

1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) is well-known to contribute "petrol" aromas to aged Riesling wines, but its prevalence and contribution to young Riesling or non-Riesling wines is not well understood. TDN concentrations were measured in 1-3-year-old varietal wines produced from Cabernet franc (n = 14 wines), Chardonnay (17), Cabernet Sauvignon (4), Gewurztraminer (4), Merlot (9), Pinot gris (6), Pinot noir (9), Riesling (28), or Sauvignon blanc (6). TDN concentrations in the Riesling wines, 6.4 ± 3.8 µg/L, were significantly higher than in all other varietals, 1.3 ± 0.8 µg/L. The odor detection thresholds for TDN were then determined in both model wine and a neutral white wine. Group sensory thresholds were found to be the same in both matrices, 2 µg/L, indicating little masking of TDN due to the odorants in the neutral white. The TDN sensory threshold was a factor of 10 below the previously reported odor threshold. On the basis of this revised threshold, 27 of 28 Riesling wines had suprathreshold TDN, whereas only 7 of 69 non-Riesling wines had suprathreshold TDN. The monoterpenes linalool and geraniol were also measured in the Riesling wines, and odor activity values (OAVs) were calculated for the monoterpenes and TDN. The OAV for TDN was higher than for the monoterpenes in 25 of 28 Riesling wines.

Comparison of odor-active compounds in grapes and wines from vitis vinifera and non-foxy American grape species.

Native American grape (Vitis) species have many desirable properties for winegrape breeding, but hybrids of these non-vinifera wild grapes with Vitis vinifera often have undesirable aromas. Other than the foxy-smelling compounds in Vitis labrusca and Vitis rotundifolia , the aromas inherent to American Vitis species are not well characterized. In this paper, the key odorants in wine produced from the American grape species Vitis riparia and Vitis cinerea were characterized in comparison to wine produced from European winegrapes (V. vinifera). Volatile compounds were extracted by solid-phase microextraction (SPME) and identified by gas chromatography-olfactometry/mass spectrometry (GC-O/MS). On the basis of flavor dilution values, most grape-derived compounds with fruity and floral aromas were at similar potency, but non-vinifera wines had higher concentrations of odorants with vegetative and earthy aromas: eugenol, cis-3-hexenol, 1,8-cineole, 3-isobutyl-2-methoxypyrazine (IBMP), and 3-isopropyl-2-methoxypyrazine (IPMP). Elevated concentrations of these compounds in non-vinifera wines were confirmed by quantitative GC-MS. Concentrations of IBMP and IPMP were well above sensory threshold in both non-vinifera wines. In a follow-up study, IBMP and IPMP were surveyed in 31 accessions of V. riparia, V. rupestris, and V. cinerea. Some accessions had concentrations of >350 pg/g IBMP or >30 pg/g IPMP, well above concentrations reported in previous studies of harvest-ripe vinifera grapes. Methyl anthranilate and 2-aminoacetophenone, key odorants responsible for the foxiness of V. labrusca grapes, were undetectable in both the V. riparia and V. cinerea wines (<10 µg/L).

Characterization of cachaça and rum aroma.

Cachaça, the most popular alcoholic beverage in Brazil, is a sugar cane spirit similar to rum. Its production is around 2 billion liters per year, of which <1% is exported. Although rum is similar to cachaça its flavor difference is easily recognizable. Using gas chromatography-olfactometry (GCO) to separate and characterize the odorants present in cachaça and rum, these two sugar cane products were compared and standards identified to use in a descriptive sensory analysis (DSA). In the DSA cachaça was more intense in the grassy, spicy, sulfury, and vinegar descriptors, whereas apple and caramel were the same in both rum and cachaça. The GCO data for the apple-smelling compounds beta-damascenone along with ethyl butyrate, isobutyrate, and 2-methylbutyrate were at the same potency in both cachaça and rum, whereas the spicy-smelling eugenol, 4-ethylguaiacol, and 2,4-nonadienal were much more potent in cachaça.

Identification of metallic-smelling 1-octen-3-one and 1-nonen-3-one from solutions of ferrous sulfate.

Taste threshold tests of ferrous sulfate (FeSO4) solutions have been confounded by the presence of putative odorants. To detect the presence of odorants released from these solutions solid-phase microextraction (SPME) was used to collect volatiles in the headspace above FeSO4 solutions. Gas chromatography-olfactometry of samples collected over three time periods (1, 5, and 16 h) and at two temperatures (22 and 37 degrees C) revealed the presence of several metallic-smelling odorants in the headspace. Using authentic standards, two of the odorants were conclusively identified as 1-octen-3-one and 1-nonen-3-one. Trace levels of other odorants were also detected, but dilution experiments indicated that 1-nonen-3-one was at least 10 times more potent than anything else released from the solutions. 1-Octen-3-one and 1-nonen-3-one are excellent candidates for the metallic odor responses often observed in threshold testing of solutions of FeSO4.