Friedrich, J.E. and Acree, T.E.
The GCO of Dairy Products.,
Analysis of the aroma pf 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: dimethylsulphone, ethyl butonoate, ethyl hexanoate, heptanal, indole, nonanal, and 1-octen-3-ol. The effect of heating cow's milk changed the aroma profile of the milk, resulting in the formation of four common odor-potent compounds: hexanal, 2-nonanone, benzothiazole, and s-decalatone. Five fermented dairy products have been analyzed by GC/O. Fermentation resulted in the formation of common odorants: 1-octen-3-one, methional, 3-ethylbutanal, 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).