This study investigated whether the suspension method (tenderstretch, TS or Achilles tendon, AT) can improve the quality of horsemeat by analyzing longissimus dorsi (LD) and semitendinosus (ST) muscles. A total of 25 horse carcasses were considered experimental units and split longitudinally, with one half suspended using the TS method and the other half using the AT method, which enabled a direct comparison within the carcass. After 7 days of aging under commercial processing conditions, the LD and ST muscles were analyzed for pH, color (L*, a*, b*), water-holding capacity (drip loss, thawing loss, cooking loss), tenderness (Warner–Bratzler shear force), and sarcomere length. Statistical analysis was performed using the MIXED procedure in SAS, with Bonferroni correction applied for post hoc comparisons. Significant differences were found between the muscles: LD had higher tenderness (39.28 N vs. 49.77 N, p = 0.0011), lower cooking loss (23.56% vs. 27.04%, p = 0.0002), and higher thawing loss (12.38% vs. 9.72%, p = 0.0021) compared to ST muscle, which had a lighter color (L* = 41.90 vs. 37.73, p < 0.0001) and longer sarcomeres (2.22 μm vs. 1.74 μm, p < 0.0001). While the TS suspension method significantly increased sarcomere length (2.05 μm vs. 1.92 μm, p = 0.0020), it did not lead to significant improvements in other quality attributes such as pH, water-holding capacity, or tenderness. The results indicate that although the TS method affects muscle structure by elongating sarcomeres (with an average difference of 0.13 μm), it does not significantly improve the overall quality of the horsemeat compared to the AT method after 7 days of aging. A combination of factors beyond suspension methods, such as optimizing aging periods or considering additional processing techniques, may therefore be required to improve horsemeat quality. This study provides insights into the specific attributes of LD and ST muscles and their response to suspension methods and contributes to a better understanding of optimizing horsemeat quality for commercial purposes.
