Structure- and Temperature-Dependent Modulation of the Partitioning of Medium-Chain Fatty Acids and Lipid-Related Volatiles by Dissolved Carbon Dioxide.

The release of lipid-related volatile compounds influences the sensory quality and stability of oil-containing foods; however, the physicochemical role of dissolved carbon dioxide (CO2) in their partitioning remains unclear. This study examined the effects of dissolved CO2 on the gas-liquid partitioning of representative lipid-related compounds, including fatty acids with carbon chain lengths ranging from C4 to C14, aldehydes, ketones, alcohols, and acetate esters, using simplified aqueous model systems. Headspace concentrations under CO2 were compared with those under nitrogen (N2) at 30-50 °C by solid-phase microextraction coupled with gas chromatography-mass spectrometry.Dissolved CO2 modulated gas-phase transfer in a structure- and temperature-dependent manner. The most pronounced differences were observed at 40 °C for medium-chain compounds, particularly C10 species such as decanoic acid and 1-decanol. The CO2/N2 headspace ratio showed a positive correlation with hydrogen-bonding capacity, although this relationship should be interpreted cautiously because other physicochemical properties may also contribute. Control experiments using O2, N2O, air, and pH-adjusted solutions suggested that the observed effects cannot be explained solely by general gas sparging or acidification.These results are consistent with the possibility that dissolved CO2 influences the balance between aqueous solvation and gas-phase partitioning, potentially through weak interactions with the hydrogen-bond network of water. The selective response of medium-chain fatty acids may have implications for understanding flavor release in carbonated and oil-containing food systems.