Interrelationships Between Visual and Instrumental Measures of Ground Beef Color

Abstract

Two experiments were conducted to understand the interrelationship among visual color score, FarnsworthMunsell values, instrumental meat color measurements, and their impact on beef color evaluation. In experiment 1, L*, a*, and b* values and various reflectance traits of the Farnsworth-Munsell 100-Hue Test tiles were measured. Incremental changes of the tiles were used to predict changes in a* values and other color variables that can be seen by a trained visual panel. Regression analysis suggests that trained panelists that 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. In experiment 2, ground beef was assigned randomly to one of 36 combinations of 3 storage temperatures, 4 storage times, and 3 display temperatures to create a variety of surface colors. A 10% change in ground beef metmyoglobin content corresponded to 3.2 units of a* (R2 = 0.95). Of all the instrumental measurements, a* (r = −0.97) and chroma (r = −0.97) best represented the red color intensity that panelists saw on the surface of ground beef. Significant surface discoloration occurred at 37.1% metmyoglobin and an a* value of 25.4 (with Illuminant A). Using a 5-point visual lean color scale, the change required in a* value for a unit change visual color score was 4.6. In conclusion, a* and chroma are highly related to visual color scores and changes in metmyoglobin, and a change in a* of 0.95 can be observed by visual panelists that have passed the Farnsworth-Munsell test.