Flavor Chemistry and Odor Thresholds

Determination of odor thresholds of components in water solution was an early method adopted by many researchers for evaluating the relative contribution of food aroma/flavor components. Some more recent methods determine odor thresholds in air added to GC effluent from flavor volatile separation. Relatively simple methods are available for calculating thresholds in air from thresholds determined in water. Similar methods can be used for calculating oil and oil-water mixture thresholds from water threshold data. The ratio of a component’s concentration in the food to its water odor threshold value has been useful in determining relative aroma/flavor importance for mostly aqueous foods. Small variations in chemical nature and structure can lead to large changes in threshold values. Water threshold values are compared for various acetyl nitrogen heterocyclic compounds, alkylhydroxyfuranones and 4-alkoxyfuranone derivatives. Even the most careful studies can lead to errors in threshold measurements. Some examples are given where threshold determination errors were caused by minor amounts of very low threshold impurities.