SOLID-PHASE EXTRACTION OF LESS VOLATILE FLAVOR COMPOUNDS FROM ULTRAHIGH-TEMPERATURE PROCESSED MILK

A rapid and sensitive, solid-phase extraction method was developed to isolate relatively nonvolatile flavor compounds from ultrahigh-temperature (UHT) milk. Various solid-phase materials were investigated including activated carbons, C18 reversed-phase silica, Florisil, and silica gel. The solid-phase materials packed in small columns (5-mL glass syringes) were treated with various solvents and loaded with the milk samples. Then, the compounds retained in the columns were eluted with methylene chloride and analyzed by gas chromatography or gas chromatography-mass spectrometry. Results indicated that the combination of activated carbon and C18 reversed-phase silica was the most effective in isolating relatively nonvolatile flavor compounds from UHT milk. Recoveries of the lactones added to milk were as low as 30 ppb, and reproducibility of the method appeared to be acceptable according to the coefficients of variation.