Descriptive analysis of complex odors: reality, model or illusion?

In order to ascertain changes in bitterness as beer aged naturally, time¯intensity (TI) measurements were made by a professional sensory panel using a squeezer transducer system. TI parameters were fitted by variance components models using Restricted Maximum Likelihood (REML). It was shown that bitterness decreased with age, although this ageinduced difference was smaller than the original differences among the eight fresh (commercial lager) beer types which spanned about 10 European Bitterness Units (EBU). Intensity-related parameters obtained from the TI curves were more important than time-related parameters for differentiating samples. Perceived bitterness could not be explained entirely by concentrations of five iso-alpha-acid peaks as measured by High Performance Liquid Chromatography (HPLC). Analytical and sensory data were correlated using Partial Least Squares (PLS2) and by fitting iso-alpha-acid peak areas in the REML models.