Selection, training and utilization of a sensory panel for the evaluation of lipolyzed flavor in milk

This research was an attempt to establish guidelines for selecting and training of sensory panelists for the evaluation of lipolyzed flavor in milk. Trained panelists were utilized in the evaluation of laboratory-prepared lipolyzed samples, retail samples, and laboratory-pasteurized samples. Gas chromatography and a titration procedure were used to evaluate the samples simultaneously with the sensory panelists.

Lipolyzed flavors in varying intensities of laboratory-prepared lipolyzed samples were not detected by the chemical methods but the trained panelists recognized the changes in the intensities. Both sensory and chemical evaluations of retail milk samples suggested that lipolyzed flavor is not a common problem in the Knoxville, TN area. Laboratory-pasteurized milk samples were slightly lipolyzed after one day of storage and moderately lipolyzed after fifteen days of storage. Good correlation between sensory scores and free fatty acids was limited to 1-day samples. Even though the titration method provided a more accurate measurement of lipolyzed flavor, it did not sufficiently account for the variation in lipolyzed flavor as evaluated by the panelists. Difficulties in sampling and the presence of other off-flavors in the 15-day laboratory-pasteurized milk may have misled the panelists, thus confounding the results. The use of samples that resemble authentically lipolyzed flavor is important.