Characterization of volatile compounds in ultra-high-pressure homogenized milk

The effect of ultra-high-pressure homogenization (UHPH) on the volatile profile of milk was studied and compared with thermal treatments. Milk was treated at 200 and 300 MPa with inlet temperatures of 30 and 40 °C. UHPH-treated milk samples were compared with high-pasteurized milk (PA; 90 °C, 15 s) and to commercial UHT, in-bottle sterilized and pasteurized milk types. Volatiles were extracted by solid phase micro-extraction and were identified by gas chromatography/mass spectrometry. Volatile profiles showed that UHPH-treated milk at 200 MPa produced fewer carbonyl compounds than PA and 300 MPa milk samples but there was a high level of hexanoic acid, related to rancid flavors. Milk treated at 300 MPa showed higher aldehyde content compared to PA milk, but lower compared with commercial milk samples (UHT, in-bottle sterilized and pasteurized). No differences were detected in relation to dimethyl sulfide. Heat treatment resulted in an increase in aldehydes and methyl ketones with increased severity of treatment. UHPH technology induced an increase in aldehydes alone.