Rapid Communication: Effect of machine, anatomical location, and replication on instrumental color of boneless pork loins

Abstract

The objective was to determine the effect of machine, anatomical location, and replication (multiple readings) on instrumental color and to characterize the amount of variation each factor contributed to overall color. Instrumental color was measured three times on the anterior and three times on the posterior end of 250 pork loins with two different Minolta CR-400 Chroma meter devices. Each Minolta was programed to use a D65 illuminant, 2° observer with an 8 mm aperture, and calibrated with white tiles specific to each machine. Therefore, a total of 12 instrumental color measurements were collected on each loin. The VARCOMP procedure in SAS was used to estimate the proportion of variation contributed by each factor to CIE L*, a*, b*, chroma, and hue. Based on previous research, the average untrained consumer is able to distinguish between 3-L* units, 0.4-a* units, and 0.9-hue angle units. Loins evaluated with machine 1 were 0.71 L* units darker (P < 0.01), 1.09 b* units more yellow (P < 0.01), 0.47 chroma units more saturated (P < 0.01), and had a hue angle 5.12 units greater (P < 0.01) than when evaluated with machine 2 but did not differ (P = 0.24) in redness. The anterior portion of the loin was lighter, less red, more yellow, more saturated and had a greater hue angle than the posterior end (P < 0.01). All color trait values decreased (P < 0.01) as replication number increased. Inherent color differences among loins contributed the greatest proportion of variability for lightness (58%), redness (57%), yellowness (70%), saturation (70%), and hue angle (49%). Machine contributed 1% variability to lightness 3% to saturation, 23% to yellowness, and 31% to hue angle (31%) but did not contribute to variability for redness. Anatomical location contributed 41% to lightness, 43% to redness, 7% to yellowness, 27% to saturation, and 31% to hue angle. Replication did not contribute to total variation for any color traits, even though it did differ among measurements. Overall, there were differences in instrumental color values between the two machines tested, but those differences were likely less than the threshold for detection by a consumer. Even so, inherent color differences between loins were a greater contributor to total variability than the differences between the two machines. Therefore, it is more important to define the location of measurements than replication or machine when using a Minolta CR-400 when performing color evaluations, assuming the settings are the same.

Nix Pro Color Sensor Comparison to HunterLab MiniScan for Measuring Lamb Meat Colour and Investigation of Repeat Measures, Illuminant and Standard Observer Effects

“…This is noteworthy as HunterLab spectrophotometers are the second most commonly used instruments for the determination of colour in meat studies (Tapp et al 2011). Methods can impact on colour data precision and reproducibility, as Barkley et al (2018) reported when pork loin colour values were shown to change as the repeat measures (readings) increased from one to three. This example demonstrates the importance of reporting the number of repeat measures when assessment meat colour to ensure the reader's comprehension when interpreting the results.…”

Evaluation of the variability of instruments used in meat color assessments

“…These findings were expected, because color values were different between machines when different operational settings were used in a previous study (Brewer et al, 2001). Additionally, Barkley et al (2018) determined that means differ between machines even when operational settings remained constant. However, both of the previous studies only investigated differences in mean values, and not variability of those readings.…”

“…To maximize replicability of instrumental color measurements, it is important to have an understanding of which variables may impact instrumental variability. Barkley et al (2018) conducted a study analyzing the effect of the machine itself on instrumental color measurements when all settings were kept constant and when loins were measured in a controlled environment. While statistical differences in color traits between machines were present, the study concluded that said differences were too small to be of practical importance and that those machines could be used interchangeably as long as each machine used identical settings.…”

“…While statistical differences in color traits between machines were present, the study concluded that said differences were too small to be of practical importance and that those machines could be used interchangeably as long as each machine used identical settings. In order to build on the findings of Barkley et al (2018), the current study was conducted to determine how purposely altering operating conditions, including machine settings and measurement environment, would affect the replicability of instrumental color readings.…”

“…When measuring instrumental color, a wide variety of operational settings exist that make replicability of measurements between groups difficult. Barkley et al (2018) reported that when settings between machines of the same model were kept constant and measurements were obtained in the same environment, differences in color traits were not large enough to be of practical significance. However, it may not always be practical for researchers or technicians to use identical settings, because not all research groups collect color data using the same equipment.…”