Colorimetry of Foods 5. Tang

Abstract

The study was undertaken to evaluate the application of the Kubelka-Munk colorant layer concept as a method of color measurement for a translucent, pulp free, carotene containing beverage of medium reflectance and high chroma. Series of samples containing small increments of canthaxanthin were ranked for color differences visually and instrumentally with a General Electric Recording Spectrophotometer and a Hunterlab D25A colorimeter. Sample thicknesses were varied and white and black backgrounds used. The panel was successful in ranking small color differences (delta E=0.25 or less). The limitation of delta E as an expression of color difference was demonstrated. Differences were expanded for very thin cells and white background presentation as a result of an increased scattering effect. Color differences for thicker cells were expanded as a result of greater absorption. These differences were reflected in the K/S ratios. High correlations were obtained for Hunter “a” and for hue with theoretical ranking. Correlations for GERS data were lower than those for Hunter data and correlations for Kubelka-Munk treatment of the data tended to be low except for the more complicated multiple correlations.