DYNAMIC HEADSPACE ANALYSIS OF LIGHT-ACTIVATED FLAVOR IN MILK

Dynamic headspace analysis (DHA) was evaluated for its ability to reco ver, fractionate and identify the key volatile compounds responsible f or development of light activated flavor (LAF) in commercial fluid mil k stored in Pyrex test tubes and exposed to 200 foot-candles of fluore scent light for 6 to 48 h at 0-5 degrees C, with and without headspace during storage. Major volatile compounds recovered and identified fro m greater than or equal to 12 h light exposed milk, presumably resulti ng from photosensitization and decomposition of riboflavin and oxidati on of lipids and sulfur compounds, included: hexanal, pentanal, dimeth yl disulfide (DMDS), 2-butanone, and 2-propanol. Formation of all five compounds was favored by providing headspace during light exposure, e xcept for 2-butanone and 2-propanol in 48 h light-exposed milk. DMDS w as not detected in 12 h light-exposed milk at steadily increasing conc entrations. DMDS formation was favored headspace during light exposure . A trained sensory panel was not able to detect LAF in 6 or 12 h ligh t-exposed milk without headspace, whereas DHA was able to detect incre ases in concentrations of two volatile compounds, i.e., pentanol and h exanal, in 12 h light-exposed milk without headspace, which correspond s to commercial milk storage conditions.