Submitted to: Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2013
Publication Date: 11/27/2013
Publication URL: http://handle.nal.usda.gov/10113/59477
Citation: Tunick, M.H., Iandola, S.K., Van Hekken, D.L. 2013. Comparison of methods for determining volatile compounds in milk, cheese, and whey powder. Foods. 2:534-543.
Interpretive Summary: Volatile compounds are responsible for much of the aroma and flavor of dairy products, and their presence and abundance may be found by using sophisticated analytical methods that involve sample heating. These techniques have not been standardized, so some compounds may be missed and false positive results are also possible. In order to identify the pitfalls that may occur, milk, whey powder, and cheese were analyzed by using these methods under different sampling conditions. Milk turns out to be particularly sensitive to temperature and sampling time, so the conditions for properly analyzing it have to be carefully monitored. Whey powder and Queso Fresco cheese are less sensitive and may be heated to a higher temperature for a shorter time, allowing for more samples to be completed in a day. The information gathered should help scientists better determine the volatile compounds leading to the characteristic aromas and flavors in dairy products.
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 conditions have to be adjusted for optimal SPME release while not generating new compounds that are absent in the original sample. Queso Fresco, a fresh non-melting cheese, may be heated at 60 deg C for 30 min, while exposure to light and elevated temperatures produces new compounds in milk. Therefore, milk samples should be heated as little as possible. 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. 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.