Inter-relationships between visual and instrumental measures of ground beef color

Two experiments were conducted to betterunderstand the practical applications of reflectance values and how instrumentalmeat color measurements are interpreted. In experiment 1, L*, a*,and b* values and various reflectance traits of the Farnsworth Munsell85-Hue tiles were measured. Incremental changes of the tiles were used topredict changes in a* values and other color variables that can be seenby a trained visual panel. Regression analysis suggests that trained paneliststhat pass the Farnsworth Munsell Hue test can discriminate a change of 0.95 in a*,0.9 in b*, and 2.54 in hue angle values when Illuminant A is used. Inexperiment 2, ground beef was assigned randomly to 1 of 36 combinations of 3 storagetemperatures, 4 storage times and 3 display temperatures to create a variety ofsurface colors. A 10% change in ground beef metmyoglobin content correspondedto 3.2 units of a* (R2 = 0.95). Of all the instrumentalmeasurements, a* (r = -0.97) and chroma (r = -0.97) best represented thered color intensity that panelists saw on the surface of ground beef. Significantsurface discoloration occurred at 37.1% metmyoglobin and an a* value of25.4 (with Illuminant A). Using a five-point visual lean color scale, thechange required in a* value for a unit change visual color score was 4.6.In conclusion, a* and chroma are highly related with visual colorscores and changes in metmyoglobin, and a change in a* of 0.95 can beobserved by visual panelists that have passed the Farnsworth Munsell test.