Chapter 9: Gas chromatography-olfactometry: Principles, practical aspects and applications in food analysis

Today, sensory aspects are the major driver for consumers' food selection. Among the sensory-active compounds in food, odorants play a major role. The olfactory profile of a food is basically determined by a comparably small number of key odorants, typically in the range of 10-20. Toward the identification of these key food odorants, gas chromatography-olfactometry (GC-O) is a key technique. With little effort, GC-O allows the screening of the volatiles isolated from a food for odor-active compounds and to distinguish them from the majority of odorless volatiles. Gas chromatography-olfactometry is based on using the human nose as a GC detector in parallel to a second detector such as a flame ionization detector or a mass spectrometer. Special care must be taken with sample preparation to avoid compound degradation and the formation of odor-active artifacts. On the basis of the GC-O results, the key odorants in a food can be determined after exact quantitation of potent odorants and calculation of odor activity values followed by sensory evaluation of odor reconstitution models. In food research, GC-O can be applied, for example, to discover novel odorants, to elucidate the molecular basis of varietal aroma differences and off-flavors and to optimize food processing, as well as to approximate odor thresholds, particularly in structure/odor relation studies.