# Intrinsic and Extrinsic Factors Affecting the Color of Fresh Beef Meat--Comprehensive Review
## 3 Results and Discussion
### Intrinsic Factors
#### 3.1.3 Muscle Position  
High color-stability muscles were defined to have a lower oxygen consumption rate, lower oxidative rancidity, and lower myoglobin content in comparison with muscles classified as color-unstable [44]. Different authors have recorded higher L*, a*, and b* readings for fresh color-stable m. longissimus lmm (LL) in comparison with color-unstable m. psoas major (PM), therefore validating the color difference between these two groups of muscles [15; 45]; however, pH differences between color-stable and color-unstable muscles were not discriminant for meat color, as shown in Table 1. It was stated that LL muscle contained more antioxidant proteins (\(\beta\)-enolase and creatine kinase) than PM muscle, significantly reducing myoglobin and lipid oxidation [46]. Previous data also suggested that higher LDH activity was representative of glycolytic muscle fibers, while higher lcdh (isocitrate dehydrogenase) activity was mostly found in oxidative muscle fibers [36]. It was also reported that higher lipid contents in color-unstable muscles proportionally increased the probability of lipid oxidation to occur [45; 46]. It was proposed that lower oxidation-reduction potential rates (ORP) could be related to less cytochrome c release, less oxidative stress, and lower oxygen consumption in LL muscle when compared to PM [8]. Higher mitochondrial integrity in ovine LL muscle resulted in lower metmyoglobin accumulation compared to PM [9]. This is consistent with other studies that found that higher metmyoglobin-reducing activity (MRA) and greater amounts of sarcoplasmic NADH in LL were associated with less accumulation of myoglobin oxidation products on meat surfaces than PM [7; 9; 47]. Lower myoglobin, iron content, and mitochondrial amounts were related to predominant type II white fibers in color-stable muscles; in contrast, a predominant presence of oxidative-type I red fibers in color-unstable muscles made them appear comparably darker [27; 48]. Lower levels of taurine and coenzyme Q10 and higher levels of carnosine, creatine, and creatinine were recorded in color-stable muscles, which were related to a higher amount of type II white fibers in comparison with color-unstable muscles [49]. Overall, variations in inherent histological functionality between different bovine muscles played a key role in meat color characterization. These differences between muscle's color stimuli can be calculated using the total color difference (\(\Delta\)E) Equation [16; 18]. \[\Delta\mathrm{E}=\sqrt{\left(\mathrm{L*}_{1}-\mathrm{L*}_{2}\right)^{2}+\left( \mathrm{a*}_{1}-\mathrm{a*}_{2}\right)^{2}+\left(\mathrm{b*}_{1}-\mathrm{b*}_ {2}\right)^{2}} \tag{1}\]  
It was stated that when \(\Delta\mathrm{E}\) values are higher than 1, color differences can be discernable by the human eye [50]. The \(\Delta\mathrm{E}\) values were calculated from several publications found in the literature, as described in Table 1. This information suggested that, overall, consumers can visually identify color variations between different groups of muscles. Thus, the meat industry needs to focus on designing innovative muscle-specific technological solutions that might prolong meat color shelf-life for a more prolonged time. Additionally, consumer-based marketing tactics should be prioritized in promoting faster consumption of those muscles described as less color-stable.