M. Kinnear  &  H.L. de Kock

Department of Food Science, University of Pretoria, Pretoria 0002, South Africa

A group of 8 individuals was selected and trained to objectively and reliably evaluate the sensory properties of 8 instant coffee samples. The trained sensory panel found significant differences among the coffee samples in terms of appearance and aroma of the dry coffee granules, aroma and flavour of the prepared coffee.  Although the panel was trained to perform similarly, clear differences were observed in their ratings for specific attributes.  Various graphical techniques, using PanelCheck, were used to evaluate the repeatability of the individuals and compare the performance of individuals compared to the rest of the panel.

Using the MSE plot, it was shown that panellists 3 and 7 were the most repeatable when assessing the appearance and the aroma of the coffee granules.  Panellists 3, 5 and 7 seemed to be more repeatable than the others when evaluating the aroma and flavour of the prepared coffee samples.  Using the p*MSE plot, it was concluded that panellist 4 was both repeatable and discriminated during the evaluation of both the dry and prepared coffee samples.  The ratings of panellist 8 were repeatable but this panellist did not distinguish between the 8 samples.  Panellist 5 was able to distinguish between the coffees but was not repeatable, while panellists 2 and 6 were not repeatable and was also not able to distinguish between the samples.  The egg shell plots showed that the panel were in good agreement concerning the coffee attributes, burnt and smokey aroma, burnt flavour, astringency, bitterness and acidity of the prepared coffee samples as well as the brown colour of the dry coffee granules.

PanelCheck provides a convenient user-friendly option to investigate trained panellist performance.  The results gathered from this post trial investigation will be helpful to plan and execute further panel training and monitoring of the trained sensory panel.

Keywords: Descriptive sensory panel, panel performance, instant coffees, PanelCheck