Effect of Milk Components on Release of Retronasal-aroma Compounds from Coffee with Milk

Abstract

The effect of milk fat (MF) and milk solids–nonfat (MSNF) on the release of retronasal-aroma (RA) compounds from coffee with milk was investigated by correlating with the lipophilicity (log k_w) of the compounds. RA compounds of a coffee flavor-added (FA) sample with MF (0 – 3%) and/or MSNF (0 – 8%) were collected by exposing a solid-phase microextraction fiber to RA simulator effluent gas and analyzed by gas chromatography-mass spectrometry (GC-MS). GC-MS analysis of volatiles released from the FA sample revealed that the relative release ratios of compounds with log k_w values >2 decreased significantly as the MF and/or MSNF content increased. Changes in relative release ratios with different MSNF contents were smaller than those with different MF contents, indicating that MF is the predominant factor affecting RA compound release. In FA samples with 0.5 – 3% MF, relationships between the relative release ratios and log k_w values could be approximated by sigmoid functions, and exponential regression models for the relative release ratios at different MF contents were obtained for compounds with log k_w >2. The resulting model for FA samples is applicable to coffee-added samples for the prediction of relative release ratios.