Gas Chromatography Olfactometry (GC/O) of Dairy Products

Abstract

Analysis of the aroma of dairy products is a complex problem due to the heterogeneous nature of milk. Several analytical methods have been used to study the aroma of dairy products; gas chromatography–mass spectrometry (GC/MS) and gas chromatography– olfactometry (GC/O) are most commonly used. In order to identify the individual odor-active compounds a bioassay that is representative of the pattern of odorants in terms of their smell activity is advantageous. Identification of these compounds is carried out using extraction, distillation, concentration and chromatography. This paper reviews the GC/O work on dairy products to date. Common odor-active compounds were found in various types of dairy products analyzed. Seven common odorants were found in four different types of raw milk: dimethylsulfone, ethyl butanoate, ethyl hexanoate, heptanal, indole, nonanal, and 1-octen-3-ol. The effect of heating cows milk changed the aroma profile of the milk, resulting in the formation of four common odor-potent compounds: hexanal, 2-nonanone, benzothiazole, and δ-decalactone. Five fermented dairy products have been analyzed by GC/O. Fermentation resulted in the formation of common odorants: 1-octen-3-one, methional, 3-methylbutanal, and butyric acid. The flavor chemistry of dairy products has been successfully analyzed using GC/O. However, further work must be conducted to produce a sample that reflects the retronasal composition of the product. This requires the use of a retronasal aroma simulation (RAS) device and/or gas chromatography olfactometry headspace (GCO-H).