Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2013
Publication Date: 9/8/2013
Citation: Tunick, M.H., Iandola, S.K., Van Hekken, D.L. 2013. Comparison of methods for determining volatile compounds in cheese, milk, and whey powder [abstract]. American Chemical Society 246th National Meeting, "Advances in the Understanding of Dairy/Cheese Flavors“. AGFD:0007.
Technical Abstract: Solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) are commonly used for qualitative and quantitative analysis of volatile compounds in various dairy products, but selecting the proper procedures presents challenges. Heat is applied to drive volatiles from the sample into the SPME fiber, from which they are injected into the GC-MS, but conditions have to be adjusted to maximize release while not altering sample composition by either charring or bacterial activity. Queso Fresco, a fresh non-melting cheese, may be heated at 60 deg C for 30 min, but aged cheese such as Cheddar is heated at 40 deg C to prevent melting. Compounds are generated in milk when exposed to light and air, so milk samples are heated at 60 deg C for only 5 min. Products such as dehydrated whey protein are more stable and can be exposed to longer periods (60 min) of warming at lower temperature (40 deg C) without decomposition, allowing for capture and analysis of many minor components. Gas flow rates are decreased to separate large numbers of compounds, but maintained as high as practical so more analyses can be run in a day. The techniques for determining the volatiles in dairy products by SPME and GC-MS have to be optimized to produce reliable results with minimal modifications and analysis times.