Isoflavones are biologically active compounds occurring naturally in a variety of plants, with relatively high levels found in soybeans. Twelve laboratories participated in a collaborative study to determine the aglycon isoflavone content of 8 test samples of soy and foods containing soy. The analytical method for the determination of isoflavones incorporates a mild saponification step that reduces the number of analytes measured and permits quantitation versus commercially available, stable reference standards. Test samples were extracted at 65°C with methanol–water (80 + 20), saponified with dilute sodium hydroxide solution, and analyzed by reversed-phase liquid chromatography with UV detection at 260 nm. Isoflavone results were reported as μg/aglycon/g or μg aglycon equivalents/g. The 8 test samples included 2 blind duplicates and 4 single test samples with total isoflavone concentrations ranging from approximately 50 to 3000 μg/g. Test samples of soy ingredients and products made with soy were distributed to collaborators with appropriate reference standards. Collaborators were asked to analyze test samples in duplicate on 2 separate days. The data were analyzed for individual isoflavone components, subtotals of daidzin–daidzein, glycitin–glycitein, and genistin–genistein, and total isoflavones. The relative standard deviation (RSD) for repeatability was 1.8–7.1%, and the RSD for reproducibility was 3.2–16.1% for total isoflavone values of 47–3099 μg/g.

Literature studies emphasize the importance of experimentally optimizing all purge-and-trap parameters to obtain adequate amounts of representative compounds for gas chromatographic analyses. Conventional "one variable at a time" evaluation of method parameters calls for exhaustive experimentation, systematically altering one variable at a time until an optimum point is attained.Response surface methodology was utilized in this study to determine the best combination of sampling parameters that maximized the amounts (with respect to proportion) of compounds isolated from dry pet foods. Purge time, sample size, and their interaction had the greatest effects on response. Quantities of volatile flavors isolated could be optimized and the sampling time could be reduced using response surface methodology.One objective for the quantitative and qualitative analyses of flavors is to correlate sensory data with instrumental results to determine flavor components of organoleptic importance. Volatile flavor compounds occur in foods in defined proportions, and they exhibit their desirable sensory attributes in given concentration ranges. Therefore, the analytical methods used to assay flavors must yield data that are reflective of the original composition of a sample. Unfortunately, the isolation and characterization of flavor compounds is very challenging because flavor compounds have trace level properties, complex nature, and diverse chemical classes.Purge-and-trap, also referred to as dynamic headspace sampling (DHS), is a means of enriching headspace gas prior to GC analyses. DHS with thermal desorption has been shown to be highly sensitive and relatively inert in the analyses of fragrances and food flavors (7-3). Cessna and Kerr (4) commented that the use of purge-and-trap systems for the analysis of aroma compounds has grown in popularity because of greater sensitivity in detecting both volatile and semi-volatile organic compounds. 22