Gas chromatography-olfactometry.

GC-olfactometry (GC-O) refers to the use of human assessors as a sensitive and selective detector for odour-active compounds. The aim of this technique is to determine the odour activity of volatile compounds in a sample extract, and assign a relative importance to each compound. Methods can be classified into three types: detection frequency, dilution to threshold and direct intensity. Dilution to threshold methods measure the potency of odour-active compounds by using a series of extract dilutions, whereas detection frequency and direct-intensity methods measure odour-active compound intensity, or relative importance, in a single concentrated extract. Factors that should be considered to improve the value of GC-O analysis are the extraction method, GC instrument conditions, including the design and operation of the odour port, methods of recording GC-O data and controlling the potential for human assessor bias using experimental design and a trained panel. Considerable emphasis is placed on the requirement for multidimensional GC analysis, and on best practice when using human assessors.