Sampling and sample preparation techniques for the determination of the volatile components of milk and dairy products

This chapter gives a description of the techniques utilized for the extraction of volatile analytes from milk and its derivatives, such as cheese and yogurt. The first part focuses on the chemical composition of the flavor of milk and dairy products, explaining the biochemical pathways and the technological factors which lead to aroma formation (glycolysis, lipolysis, proteolysis, and addition of starter cultures). An overview on the sample preparation techniques is given, from the conventional (i.e., solvent extraction and distillation) up to the most advanced (purge and trap, SPME), discussing benefits and drawbacks. Finally, an extensive summary of the most significant applications for each technique is presented, emphasizing objectives, analytical methods, and findings of the studies retrieved from the recent literature. Examples of applications are: characterization of the flavor constituents of cheese of various origins, determination of off-flavor in infant formula milk, assessment of relationships between the starter culture used and the qualitative composition of the flavor, and monitoring the volatile fraction of dairy products depending upon variables such as productive season and geographic origin.