This unit discusses the use and design of the two mouth simulators, the retronasal aroma simulator (RAS) and the model mouth, that have successfully been verified to produce an effluent with volatile ratios similar to that found in human exhaled breath during eating. Though at a glance the apparatuses seem very different, they produce relatively similar effluents. Of obvious notability is the difference in the size of the reservoir; the RAS reservoir is 1 liter and the model mouth reservoir is 70 ml. When determining which apparatus to use, carefully consider concentration needs, absorption characteristics of compounds, and shear resistance of the food. Figure G1.7.1 is a comparison of chromatograms from a solid-phase microextraction (SPME) from a beverage in a sealed container and from the same beverage in a mouth simulator. This comparison demonstrates that a very different volatile ratio is produced from the same food under different sampling conditions. Due to these differences, it is important to use a sampling method that simulates mouth conditions when studying flavor compositions that produce a human perception. Most methods intended to increase headspace volatile concentration, such as adding salt for salting out, do not uniformly affect volatility. For some compounds,
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