Correlation between muscle fiber type, muscle-to-fat ratio, and physicochemical properties in pork belly and mokshim (neck)

The purpose of this study is to measure the muscle and fat ratio of mokshim (neck, Boston butt equivalent) and pork belly using computed tomography (CT) and magnetic resonance imaging (MRI), and to provide basic data that can be used for quality evaluation by comparing it to the traditional pork quality assessment indicator, the physicochemical properties. A total of 115 pork mokshim and pork belly were scanned by CT, while 30% (33 samples of pork) of them were imaged by MRI. The ratios of muscle-to-fat were estimated using Vitrea workstation version 7. The muscle-to-fat ratio of mokshim measured by CT and MRI showed comparable values of 1:0350 and 1:0.325, respectively. The correlations between physicochemical properties and non-destructive assessment methods, including CT, MRI, and histochemical staining, were evaluated using GraphPad Prism version 8. The muscle-to-fat ratio in the mokshim measured by CT showed a significant negative correlation with cooking loss (r = −0.226, <italic>p</italic> < 0.05), and positive correlations with moisture content (r = 0.203, <italic>p</italic> < 0.05) and yellowness (b*) (r = 0.220, <italic>p</italic> < 0.05). In the pork belly, the muscle-to-fat ratio also showed a significant positive correlation with b* (r = 0.411, <italic>p</italic> < 0.001).  In contrast, no significant correlation was observed between the muscle-to-fat ratio measured by MRI and any of the physicochemical properties. Similarly, no significant correlations were found between muscle fiber type Ⅰ and physicochemical properties across all belly regions. However, significant associations were observed between muscle fiber types and meat color in the pork belly. Type ⅡA Fibers showed negative correlations with lightness and yellowness, whereas Type ⅡB fibers showed positive correlations with these color traits. These results suggest a potential relationship between muscle fiber composition, muscle-to-fat ratio, and pork quality traits. However, further studies with larger sample sizes are needed to confirm these findings.