Evaluation of R-indices for preference testing of apple juices

Abstract

New hedonic consumer evaluations, based on signal-detection theory, were examined using three sensory panels [consumer ( n = 256), ‘experienced taster’ ( n = 36), ‘proprietary’ ( n = 36)] and four apple juices. For each panel, half the panellists rated and the other half ranked the apple juices. Scale and panel performance were evaluated by comparing Friedman's rank-sum preference scores and by calculating R-indices. For the consumer panel, results from the rated and ranked analyses were similar, with juices having the same relative order of preference. Although the children as a group ( n = 78), were non-discriminating, the adults ( n = 178) significantly differentiated the juices, disliking one juice from the others. Small panel size as well as proprietary bias markedly affected the stability of the R-index. Results from ‘experienced’ and ‘proprietary’ panels were not effective indicators of consumer response. Differences in juice preferences, between the consumer and other panels were attributed to proprietary bias, expectation error, and differences in sample size ( n). R-indices and mean preference scores for the consumer panel were highly correlated ( r > 0.98), for both ranking and rating data, and were believed to monitor the same underlying variation. The R-index, however, provided alternate information to conventional preference methodologies and was believed to be an important complement to the existing sensory methodologies.