Estimation of the oil water partition coefficient, experimental and theoretical approaches related to volatile behaviour in milk

Oil/water partition coefficients (Kow) of 20 volatile compounds in model or milk-based emulsions were determined experimentally using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). The Kow values were estimated by comparing the headspace concentration of volatiles above solutions with different lipid content (2, 7, 12, 27, 62 and 102 g/L). This involved curve fitting of a series of the six experimental values to an equation describing the expected behaviour of volatiles in lipid containing systems. Alternatively, a simpler experimental method based on the comparison of only two samples was used. Overall, the Kow values determined in the milk-based emulsion were the same as those found in simple model emulsions, suggesting that the partitioning behaviour of volatiles between air and the two emulsion systems was the same. The Log P values of the 20 volatile compounds were calculated using four software programmes, the Log P values from EPI Suite™ were found to correlate best with experimental Log Kow values.