COLORIMETRY OF FOODS. 3. Carrot Puree

Abstract

SUMMARY– A series of 10 carrot purees was prepared with added FD&C Green No. 1 food color in increments of 0.015 ppm. The samples were evaluated visually for color differences under illumination of 7400°K and measured with a G.E. spectrophotometer with D&H tristimulus integrator and a Hun terlab D25 colorimeter in cells varying from 2–8 mm in thickness against both a white and black background. The instrumental data were calculated in conventional and K/S ratios and correlated with visual and theoretical rankings. The panelists could reasonably well rank samples differing by 0.10–0.15 delta E units, calculated as [(delta L)2+ (delta a)2+ (delta b)2 1/2. Highest correlations with the theoretical order were obtained with a black background and sample thicknesses of 6 mm or more. Adequate rankings with either instrument required a multiple correlation with all 3 color parameters (X Y Z or L a b). Optimum separation of samples with the G.E. spectrophotometer was obtained with a white background and a sample thickness of 5 mm or more. The Hunterlab D25 colorimeter was superior to the G.E. spectrophotometer for separation of samples. Optimum separation was with a 2‐in.‐diameter aperture and a cell 4 mm or more in thickness against a white background. Correlations of Hunter data with theoretical order were higher than those with visual vs. theoretical ranking. Individual K and S values may be useful in characterizing purees for colorimetry.