PRINCIPAL COMPONENT ANALYSIS OF TIME-INTENSITY BITTERNESS CURVES1

Perceived bitterness in drinks is known to fade slowly over time. Time-Intensity curves are a means of studying this fading process. K subjects record the perceived bitterness intensity by moving a slider on a monitor using a mouse. Usually average TI-curves are calculated to give a representation of the TI-curve for one particular object. The problem is that there often are large individual differences, so the average TI-curve is not always a good representation. An alternative is to perform a Principal Component Analysis on the matrices of objects by individual TI-curves for each object. The resulting, so-called, Principal Time Intensity Curves (PTIC's) are better representations than the average curves. Often the PTIC's for the different products are hard to distinguish. In this case a noncentered PCA of the matrix with curves gives results which show more differences between the products.