Subjective Pink Threshold
Establishment of a subjective pink threshold was an
important step toward setting a cutoff for judging the
existence of pinking during the experiment. Table 1 presents
instrumental color values of the cooked samples examined
to establish the pink threshold. Visual appraisal
of the cooked samples in the light booth showed all the
samples injected with nitrite to have pink discoloration.
Samples injected with only 1 ppm of sodium nitrite had
a light pink discoloration that was distinguishable from
a control sample injected with sodium chloride only. Samples
injected with 1 ppm sodium nitrite and 1% sodium
chloride were compared to the controls injected with 1%
sodium chloride; this comparison resulted in establishing
the least discoverable visible pinking in cooked samples.
During the six replications, a* values ranged from 3.79
to 3.85 for the 1 ppm level. Statistical analysis showed no
significance for L* and b* between samples injected with
different sodium nitrite levels (with the exception of thecontrol sample). The a* value of the sample injected with
1 ppm of nitrite differed from those injected with 3, 4, or
5 ppm but not from that injected with 2 ppm. In samples
injected with 4 or 5 ppm, a* values were significantly
different from the rest of the samples. The change in a*
value was accompanied by change in hue angle, which
decreased from 72.86° in 1 ppm to 67.05°in 5 ppm sample.
Chroma values were similar for all the pink samples and
ranged from 12.26 to 13.12. The highest chroma value
(16.13) and hue angle (80.65°) were found in the control
sample. The results indicate that among pink samples,
the a* value, but not L* or b* values, were affected by
nitrite. Thus, when chroma values were similar, a* value
seemed to cause the most changes in hue angle. Therefore,
a* is the best choice to use as the threshold value within
the range 79 to 84 for L* value and 10 to 16 for b* value.
Previous research (Heaton et al., 2000) had also confirmed
that the a* value correlates well with sensory (visual)
scores of meat color. A comparison of results from a visual
examination and colorimetric data established the least
visible pinking at a* = 3.8. This value represents an average
value from six replications. The pink threshold presented
here is even lower than the a* values > 4.0 for
white meat reported by other authors