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Last Update: 01/31/00

Changes in Volatile Organic Composition In Milk Over Time

 INTRODUCTION

Volatile and semi-volatile organic compounds present both in the matrix and the headspace aroma are largely responsible for the flavor qualities of the foods we eat. Flavor is always considered the most important factor of any of the quality categories when comparing various dairy products. Dairy products provide a great sense of eating pleasure for their characteristic flavor and smooth taste as well as have an important role in a well balanced diet. Because milk possesses a bland and soft flavor, the appearance of an objectionable off-flavor or off-odor is readily noticeable. There is a delicate balance between many flavor compounds that produce a desirable milk flavor and if this balance is disturbed, off-flavors may occur. In assessing its overall flavor quality, it would be extremely advantageous to have a reliable and efficient method for the detection, identification and quantification of the volatile organic compounds responsible for the degree of freshness in milk.

Analytical techniques are needed to profile a wider range of volatile and semi-volatile organics in milk and to identify the flavors, off-flavors, off-odors and potential contaminants that may be present. The purpose of this investigation is to develop an analytical technique that could detect and identify a wide range of volatile and semi-volatile compounds in milk over time and relate the differences in volatile organic composition to the quality of milk. For this study, volatile organic compounds were purged from samples of milk followed by trapping onto Tenax® TA adsorbent resin using a dynamic purge and trap technique (P&T). The adsorbent traps were subsequently analyzed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). The dynamic P&T technique together with TD-GC-MS permits the analysis of a wider range of both volatile and semi-volatile organic compounds and is more sensitive than the routinely used static headspace techniques, cryofocusing techniques and high resolution GC.

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