Evaluation of the variability of instruments used in meat color assessments

The study objectives were to determine how different instrumental settings and measurement environments affect the means and variability of instrumental muscle color in pork loins and Boston butts (serratus ventralis). Three studies were conducted testing different variables; study 1 tested aperture type (closed vs. open), study 2 tested illuminant (D65 vs. C), and study 3 tested measurement environment (commercial facility vs. university; loins only). Within each set of loins and Boston butts, the 100 greatest and lowest lightness (L*), redness (a*), and yellowness (b*) measurements were determined for each machine/setting combination. Color data within a set were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). Variances and coefficient of variation were calculated using the MEANS procedure. Coefficients of determination between machines within a set were calculated using the REG procedure. L* and a* measurements in loins and Boston butts were more variable when using an open aperture than a closed aperture (P ≤ 0.02). Illuminant did not affect L* or a* variability in either muscle (P ≥ 0.16). In loins and Boston butts, measurements from machine 1 explained 11% – 54% (P < 0.0001) of variation in machine 2 measurements when settings differed, and there was 17%–65% agreement between machines for extreme values. In loins, machine 1 measurements explained 41%–49% (P < 0.0001) of variation in machine 2 measurements under commercial conditions and 86%–92% (P < 0.0001) under controlled conditions. With identical settings, there was 49%–73% agreement between machines for the greatest and lowest 100 values under commercial conditions and 84%–90% agreement under university conditions. Overall, using a closed aperture decreased overall color variability compared with using an open aperture. However, it is difficult to compare studies measuring instrumental color when operational settings differ or the environment is not well controlled.