Karamucki Tadeusz, Jakubowska Małgorzata
Department of Microbiology and Biotechnology, West Pomeranian University of Technology, Szczecin, Poland.
Acta Sci Pol Technol Aliment. 2021 Oct-Dec;20(4):485-496. doi: 10.17306/J.AFS.0971.
In pork colour measurements, the value of each parameter depends on the type of illuminant used. The spectra of D65 and A illuminants show great differences, with illuminant A having greater emission in the red part of the visible spectrum. Therefore, its application in the colour measurements of the pork longissimus muscle should result in larger changes in redness (Δa*) and hue angle (Δh°) and higher correlation between Δa* and Δh° and pH48 and WHC. The purpose of this study was to compare the suitability of the illuminant/observer systems D65/10° and A/10° for colour measurements of pork longissimus muscle, using the CIELAB and CIELCh systems.
The study involved 168 samples of longissimus lumborum muscle taken from 168 carcasses (mean weight 90.2 ±6.0 kg) of pigs slaughtered on an industrial processing line. The moisture content, crude protein, intramuscular fat content, WHC, and pH48 were determined. Colour measurements using CIELAB and CIELCh scales were carried out with both D65/10° and A/10° illuminant/observer systems and reflectance measurements. The chromatic absorbance value at 525 nm (A525p) and the relative amounts of MbO2, MetMb, and Mb were calculated according to methods proposed by Krzywicki (1979) and AMSA (2012). Meat samples were illuminated and differences in the values of colour parameters (ΔL*, Δa*, Δb*, ΔC*, Δh°), chromatic absorbance at 525 nm (ΔA525p), and in the relative amounts of chemical forms of myoglobin (ΔMbO2, ΔMetMb, ΔMb) were determined. In addition, hue difference (ΔH) and total difference (ΔE) were calculated.
The values of correlation coefficients between moisture content (especially crude protein and intramuscular fat, and colour parameters) were low and often statistically insignificant. Higher and mostly significant values of correlation coefficients were found between colour parameters and WHC and pH48. The A/10° system resulted in higher values of correlation coefficients than D65/10° between (I) WHC, pH48 and (II) h°, Δa* and Δh°. At the same time, in the A/10° system the combined effect of the relative amounts of myoglobin chemical forms on the variation of h° values and the combined effect of changes (Δ) in their amounts on the variation of Δh° and ΔH and ΔE were greater than in D65/10°, with the greatest effect of these changes (Δ) in the amount of MetMb.
Replacement of the illuminant/observer D65/10° system with the A/10° system in colour measurements of raw pork longissimus muscle changed the proportion of pigments and the relative number of chemical forms of myoglobin in influencing the values of colour parameters, primarily h°. Therefore, using the A/10° system for colour measurements allows us to better capture the differences (Δ) in redness Δa* and especially in hue angle (Δh°), as well as hue difference (ΔH) and total difference (ΔE), with an increase in the relative amount of MetMb becoming the main determinant of these differences (Δ). At the same time, measurements using the A/10° system increased the correlation coefficients between WHC and pH48 and changes in redness (Δa*) and hue angle (Δh°). Therefore, the A/10° system compared to the D65/10° system may be more useful for measuring the colour stability of raw pork, especially the determination of Δh° and ΔH and ΔE. >.
在猪肉颜色测量中，每个参数的值取决于所使用的光源类型。D65和A光源的光谱显示出很大差异，A光源在可见光谱的红色部分发射更强。因此，将其应用于猪背最长肌的颜色测量时，应会导致红度（Δa*）和色相角（Δh°）有更大变化，且Δa*与Δh°以及pH48和滴水损失（WHC）之间具有更高的相关性。本研究的目的是使用CIELAB和CIELCh系统，比较D65/10°和A/10°光源/观察者系统对猪背最长肌颜色测量的适用性。
本研究涉及从在工业加工线上屠宰的168头猪（平均体重90.2 ±6.0 kg）的168个猪胴体上采集的背最长肌样本。测定了水分含量、粗蛋白、肌内脂肪含量、滴水损失和pH48。使用D65/10°和A/10°光源/观察者系统以及反射率测量，采用CIELAB和CIELCh量表进行颜色测量。根据Krzywicki（1979年）和美国肉类科学协会（AMSA，2012年）提出的方法，计算了525 nm处的色度吸光度值（A525p）以及氧合肌红蛋白（MbO2）、高铁肌红蛋白（MetMb）和肌红蛋白（Mb）的相对含量。对肉样进行光照，并测定颜色参数（ΔL*、Δa*、Δb*、ΔC*、Δh°）、525 nm处的色度吸光度（ΔA525p）以及肌红蛋白化学形式的相对含量（ΔMbO2、ΔMetMb、ΔMb）的差异。此外，还计算了色相差异（ΔH）和总差异（ΔE）。
水分含量（尤其是粗蛋白和肌内脂肪）与颜色参数之间的相关系数值较低，且通常无统计学意义。在颜色参数与滴水损失和pH48之间发现了更高且大多具有统计学意义的相关系数值。在（I）滴水损失、pH48和（II）h°、Δa*和Δh°之间，A/10°系统的相关系数值高于D65/10°系统。同时，在A/10°系统中，肌红蛋白化学形式的相对含量对h°值变化的综合影响以及其含量变化（Δ）对Δh°、ΔH和ΔE变化的综合影响大于D65/10°系统，其中MetMb含量的这些变化（Δ）影响最大。
在生猪肉背最长肌的颜色测量中，用A/10°系统替代D65/10°光源/观察者系统，改变了色素比例和肌红蛋白化学形式的相对数量对颜色参数值（主要是h°）的影响。因此，使用A/10°系统进行颜色测量可以使我们更好地捕捉红度Δa尤其是色相角（Δh°）方面的差异（Δ），以及色相差异（ΔH）和总差异（ΔE），MetMb相对含量的增加成为这些差异（Δ）的主要决定因素。同时，使用A/10°系统进行测量增加了滴水损失和pH48与红度变化（Δa）和色相角变化（Δh°）之间的相关系数。因此，与D65/10°系统相比，A/10°系统可能更有助于测量生猪肉的颜色稳定性尤其是Δh°、ΔH和ΔE的测定。
