American rye whiskey is a distilled, alcoholic beverage, manufactured and consumed in the United States since before the Revolutionary War. Although other whiskeys (Scotch, Irish, bourbon) have been studied extensively in recent years, the aroma profile and potent odorants of American rye whiskey have not been reported. Two dilution analysis methods for Gas Chromatography-Olfactometry (GCO) were used to identify the potent odorants in rye whiskey: Sample Dilution Analysis (SDA) – a novel, nonextractive, direct method of analyzing alcoholic distillates – and Aroma Extract Dilution Analysis (AEDA) – a widely used and well-understood extractive method. SDA was found to provide equivalent results to AEDA while reducing analysis time and avoiding extraction bias. American rye whiskey was found to be a complex aroma system, with no-one odorant responsible for its characteristic aroma, but among the
key aroma compounds identified were: 3-methyl-1-butanol, 2-phenylethanol, cis-(3S,4S)-whiskey lactone, guaiacol, syringol, and vanillin. These compounds likely mainly originated from either yeast
metabolism (in the case of fusel alcohols) or lignin pyrrolysis. Odorants identified as important through dilution analysis were then quantified using Stable Isotope Dilution Analysis (SIDA). All key odorants were quantified, with concentrations ranging from 2560 ppm (3-methyl-1-butanol) to 7 ppb (ethyl cinnamate). In addition, acetaldehyde was identified as a key odorant, and quantified using external
standardization. Finally, model solutions based on the quantification were constructed and compared to authentic whiskey samples using a difference test: the R-Index by Rating method. It was shown that naïve judges were unable to discriminate between different brands of commercial whiskeys. These judges were also unable in some but not all cases to discriminate between the model and the commercial whiskeys, indicating that the model and the quantification it was based on were a partial success, but that further work is necessary
