COLORIMETRY OF FOODS. 2. Color Measurement of Squash Puree Using the Kubelka‐Munk Concept

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Abstract
SUMMARY: A series of 10 squash purees was prepared with added canthaxan thin in increments of 0.3‐ppm. The samples were evaluated visually for color differences under illumination of 7400°K and measured with a G.E. spectrophotometer with tristimulus integrator and a Hunterlab 025 calorimeter. Each sample was measured against a white and a black background in Plexiglass cells varying in thickness from 2 to 8 mm for both visual and instrumental experiments. The instrumental data were calculated in conventional and K/S ratios and correlated with theoretical and visual color rankings. The optimum visual rankings were found with a 5‐mm thickness or greater, and a black background. The panels could rank samples differing in approximately 0.2 delta E units, calculated as Δ E = (ΔL2+Δa2+Δb2)½ reasonably well with 5mm thickness or greater, and no better with thinner cells, even though the ΔE values were much larger. Adequate rankings of the samples by either instrument required a multiple correlation with all three color parameters (X Y Z or L a b). Calculation of tristimulus data in terms of K/S ratios or K/S ratios at single wavelengths did not improve the correlations with visual or theoretical rankings.

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