Edward H. Lavin

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).

Aroma analysis of coffee brew by gas chromatography-olfactometry

Abstract During the study of coffee flavor, the processes of brewing, extraction and sampling cause losses of the aroma compounds present in coffee grounds. In this study, coffees from two brewing methods were extracted, serially diluted and each dilution sniffed twice using the gas chromatography-olfactometry (GCO) technique called CharmAnalysis™. Among the hundreds of volatile chemicals present, 18 of the thirty most potent odorants were identified by comparing the mass spectra, odor activity and Kovats retention indices with those of authentic standards. Our studies have verified the presence of previously identified aroma compounds among the most potent odorants in coffee and show the differences between the two brewing methods tested.

Gas Chromatography—Olfactometry (GC/O) of Vapor Phases

Aroma is a perception of a response to certain chemicals when they are present above their detection threshold in the vapor phase as they come in contact with receptors in the olfactory epithelium. The response to odor active volatiles (odorants) that enter through the nostrils (orthonasal sensation) from a food is often different from the perception resulting from volatiles that enter from the mouth and respiratory system (retronasal sensation). This is due to different physical and chemical conditions that affect flavor release from the food system in the mouth (e.g. pH, enzymes, temperature, mastication) (Roberts and Acree, 1995). Figure 1 illustrates these two different pathways. An orthonasal aroma composition can be represented by static headspace like that experienced when a bottle of wine is first opened and sniffed, or a dynamic system such as smelling wine in a glass after it has been poured. In contrast, the odor of wine as it is drunk is a retronasal aroma and always results from the dynamic release of odorants. Both the odorant concentrations and their ratios are different in equilibrium and dynamic systems, therefore the appropriate measurement must be chosen (Roberts and Acree, 1996).

Solid Phase Microextraction Application in GC/Olfactometry Dilution Analysis

Aroma chemicals, perceived on the olfactory epithelium, impart an odor character to food. Among the hundreds of volatile compounds in natural foods, only a small fraction contribute to the perceived aroma because aroma compounds must be present above their detection threshold to impart a sensation. Additionally, aromas are volatiles, but not all volatiles cause aroma sensation. Over 500 compounds that cause an aroma sensation have been identified as described on the Flavornet (http://www.nysaes.cornell.edu/fst/faculty/acree/flavornet/index.html) and the characteristic flavor of a particular food comes from the pattern of aroma compounds volatilizing from food.

A Savory Odorant in Sweet Potato Shochu: 2-Methyl-3-(Methyldithio)-Furan

IntroductionThe purpose of this work is to determine the key odorants (KO) in shochu, a Japanese spirit made from sweet potato, barley, rice, soba, or sugarcane extract fermented with 20% rice koji. Each carbohydrate source produces a mild flavored spirit, but sweet potato produces shochu with a strong savory character.MethodsThe KOs released by sweet potato, barley, rice, and sugarcane shochus were determined using headspace solid-phase micro-extraction (HS-SPME), gas chromatography-olfactometry (GC-O) dilution analysis to determine aroma characteristics, gas chromatography-mass spectrometry (GC-MS), and authentic standards to determine identity.ResultsThe five top KOs found in sweet potato shochu were ethyl octanoate, ethyl cinnamate, 2-methyl-3-furanthiol, β-damascenone, 2-methyl-3-(methyldithio)-furan. The five top KOs in barley, rice, and sugarcane shochus were ethyl octanoate, ethyl hexanoate, isoamyl acetate, ethyl 2-methylbutanoate, and ethyl isobutyrate.ConclusionThe unique savory aroma of sweet potato was found to have higher levels of ethyl cinnamate, 2-methyl-3-furanthiol, and 2-methyl-3-(methyldithio)-furan while the five top KOs in barley-, rice-, and sugarcane-derived shochus were esters common in most alcoholic fermentations.ImplicationsThere is growing evidence that a small number of odorants determine our perception of food aroma. The first challenge is to determine what these key odorants are and second to determine the rules used by the olfactory system to create odor images. This research identifies candidates for the unique aroma of sweet potato shochu.

The Perception of Riesling Varietal Character: The Role of 2,2,1-Trimethyl-Dihydronaphthalene (TDN)

The perception of wine aroma is an excellent example of the human ability to experience multiple sensations as a single gestalt, i.e. a configural perception or as a top-down process. For example, the same wine recognized as Riesling could, after some time spent on analysis, yield, “This Riesling has a moderate petrol aroma and a faint lemon smell.” Recent studies of binary mixtures showed that only similar odors cross-adapt while dissimilar odors suppress each other in mixtures, indicating a possible explanation for the suppression of fruity/floral by 2,2,1-trimethyl- dihydronaphthalene (TDN) in Riesling.