Panel performance monitoring by Poincare plot: A case study on flavoured bottled waters

The application of the Poincare method is discussed on the field of sensory panel performance monitoring. The Poincare plot evaluates and visualizes the difference from the consensus for each panelist even for one product and for one attribute. Sensory tests were carried out on 5 commercially available brands of pear-lemon and josta flavoured bottled waters. Several sensory parameters were assessed and a complex dissimilarity index was calculated. Based on this index the attributes and panelists can be ranked highlighting the attribute which was the hardest to evaluate and the most consistent panel member. Our method has been compared to the other methods using the sum of ranking difference method and cross-validated by leave-one-out technique. Regarding both the ranking of the panelists and the ranking of the attributes significant differences were found between the Poincare method and the traditional techniques since the sum of ranking difference was greater than the critical value of 39 and 79 at 5%, respectively. Only the Poincare method was able to indicate sweet flavour as the easiest attribute to evaluate. Free R code is available to carry out the calculations and apply this method.