Colorimetry of Foods. 1. Correlation of Raw, Transformed and Reduced Data with Visual Rankings for Spinach Puree

SUMMARY — Freshly processed spinach puree and stored processed puree were mixed in proportions varying from O to 100% in increments of 10% to provide three different sets of 11 samples each. These sets simulated the range of color values actually obtained with samples in storage after processing. Color measurements were performed by means of a General Electric Recording Spectrophotometer, a Hunterlab Model D25 Color Difference Meter, and a Colormaster Differential Colorimeter, Model V. Experiments were carried out on each set of samples to obtain tristimulus values from each instrument. These values were mathematically transformed to the tristimulus values of the other two color systems. Tristimulus values from the instruments also were reduced to common color functions, and all data were correlated with visual rankings. Good correlations of instrument versus visual rank were obtained. Absolute values obtained from the transformation equations were very different from instrumental values. However, the transformations resulted in only a slight decrease in correlation with visual preference. Reduced data calculated from instrumental read‐out correlated well with visual rank. However, conversion of Colormaster data to Adams data and resultant reduction produced poor correlations.