With the increasing consumer demand for high-quality mutton, the mechanisms underlying mutton flavor formation have received growing attention. Meat flavor is closely associated with volatile flavor compounds, lipid metabolites and amino acid precursors. Technologies such as electronic nose, electronic tongue, flavoromics, lipidomics and amino acid analysis provide effective approaches for characterizing flavor profiles. Linxia mutton sheep are an important regional genetic resource with notable meat-quality advantages; however, the mechanisms responsible for their characteristic flavor remain insufficiently understood. Therefore, this study compared meat quality and flavor differences between Linxia mutton sheep and Hu sheep by integrating the above techniques, aiming to reveal the biochemical basis of the characteristic flavor of Linxia mutton sheep and provide a theoretical foundation for the development of high-quality mutton and flavor regulation.

Healthy 7-month-old male lambs of Hu sheep and Linxia mutton sheep, raised under the same feeding conditions, were selected and assigned to the Hu sheep group (H group) and Linxia mutton sheep group (L group), respectively. After slaughter, the longissimus dorsi muscle was collected to determine slaughter performance and meat-quality traits, including pH and meat color. Amino acids, volatile flavor compounds and lipid metabolites were further analyzed using an amino acid analyzer, electronic nose, electronic tongue, HS-SPME-GC-MS and UPLC-MS/MS. Data were expressed as mean ± SEM. Independent-sample t-tests, principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used for statistical analysis.

The results showed that the L group was generally superior to the H group in growth performance and meat nutritional quality. Compared with the H group, the L group had significantly higher pre-slaughter live weight, carcass weight, eye muscle area and crude protein content. In contrast, the H group showed significantly higher backfat thickness, GR value, intramuscular fat content and shear force, indicating stronger fat deposition but relatively poorer tenderness. Amino acid analysis showed that total amino acids, essential amino acids and non-essential amino acids were all significantly higher in the L group than in the H group. Both electronic nose and electronic tongue analyses clearly distinguished the two groups, and the L group showed better umami, sweetness, saltiness and richness. Further analysis identified 69 volatile compounds and 1, 151 lipid metabolites, from which four key characteristic flavor compounds were screened. In the L group, carnitine, some phospholipids and sphingolipids were mainly up-regulated, whereas the H group was characterized by triglyceride enrichment. Correlation analysis showed that the four characteristic volatile compounds were significantly negatively correlated with triglycerides but significantly positively correlated with carnitine and other lipid metabolites, suggesting that differences in lipid metabolism may be the most important material basis for flavor differentiation between the two sheep breeds.

The stronger muscle growth and protein deposition capacity of Linxia mutton sheep not only improved the nutritional value of the meat but also provided a richer material basis for flavor formation. The superior meat quality of Linxia mutton sheep may be closely related to their nutrient deposition pattern and metabolic characteristics of flavor precursors. The enrichment of taste-active amino acids may enhance umami perception and contribute to the formation of characteristic flavor through participation in the Maillard reaction. Meanwhile, differences in lipid metabolism indicated that Linxia mutton sheep may be more inclined to form a metabolic environment favorable for the generation and release of volatile flavor compounds. Therefore, it can be inferred that the synergistic effects among protein deposition, amino acid transformation and lipid metabolism may be an important mechanism driving the formation of the superior flavor quality of Linxia mutton sheep.