Flavor release of diacetyl and 2-heptanone from skimmed and full fat milk under mouth conditions

To gain insight into the process of retronasal olfaction, flavor release from skimmed milk and full fat milk (containing 3.75% fat) was investigated using a model mouth system with a screw plunger. Large differences were determined in the quantity of flavor released using two different methods: with screw plunger movement, which represents "retronasal" flavor release, and without the screw plunger, which represents "orthonasal" flavor release. The screw plunger motion accelerated the release of diacetyl and 2-heptanone in both skimmed and full fat milk. The amount of diacetyl released was not influenced by the fat content of the milk in either case (with or without screw plunger operation), while the amount of 2-heptanone released was lower in full fat milk both with and without screw plunger motion. The influence of fat content on the amount of flavor released was explained by the lipophilicity of the flavor components, and mass transfer also contributed to release of the hydrophilic flavor compound.