Beef colour is essential to consumer acceptability with dark muscle colours being problematic. Dark meat has less light scattering but the mechanisms are unknown. We hypothesise that three mechanisms are responsible for decreased light scattering in dark meat, namely (i) larger lateral separation of myofilaments, (ii) decreased optical protein density in the I-band and (iii) decreased denaturation of sarcoplasmic proteins. Nineteen beef longissimus thoracis muscles, divided into ‘light’, ‘medium’ and ‘dark’ colour groups, were assessed for light scattering by reflectance confocal microscopy, sarcomere length, and myofilament lattice spacing by small-angle X-ray diffraction. Dark muscles had a longer lattice spacing, shorter sarcomeres and wider muscle fibre diameters compared to lighter colour groups, indicating that the transverse spacing of muscle fibres that occurs post-mortem, with pH decline, is central to light scattering development. Dark muscles also had more degradation of the Z-disc and higher sarcoplasmic protein activities, which could impact on the optical density and contribute to lower light scattering.

牛肉的颜色对于消费者的可接受性至关重要，而深色肌肉则是有问题的。黑肉的光散射较少，但机理尚不清楚。我们假设三种机制可导致减少黑肉中的光散射，即（i）肌丝的较大横向分离，（ii）I波段中光学蛋白密度降低和（iii）肌浆蛋白变性降低。十九个牛肉longissimus thoracis通过反射共聚焦显微镜，分为小节X射线衍射的肌层，肌节长度和肌丝晶格间距，对分为“浅”，“中”和“暗”色组的肌肉进行了光散射评估。与较浅的颜色组相比，深色肌肉具有更长的晶格间距，较短的肉瘤和较宽的肌纤维直径，表明验尸后发生的肌纤维横向间距（pH下降）是光散射发展的中心。黑肌肉还具有更多的Z盘降解和更高的肌浆蛋白活性，这可能会影响光密度并有助于降低光散射。