Structure- and Temperature-Dependent Modulation of the Partitioning of Medium-Chain Fatty Acids and Lipid-Related...

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.