There are limited reports about the effect of different heat treatments on the quality and flavor of Black Tibetan sheep meat. The current study examined the effect of pan-frying, deep-frying, baking, and boiling treatment on the quality of Black Tibetan sheep meat; the amino acid, fatty acid, and volatile flavor compounds (VFCs) were investigated by a texture analyzer, ultra-high-performance liquid chromatography (UHPLC), gas chromatography (GC), and headspace-gas chromatography-ion mobility (HS-GC-IMS). The key VFCs were identified through orthogonal partial least squares discrimination analysis (OPLS-DA), and variable importance projection (VIP) values. In addition, Pearson’s correlations between meat quality parameters and key VFCs were examined. The sensory scores, including texture, color, and appearance, of baked and pan-fried meat were higher than those of deep-fried and boiled meat. The protein (40.47%) and amino acid (62.93 µmol/g) contents were the highest in pan-fried meat (p < 0.05). Additionally, it contained the highest amounts of monounsaturated and polyunsaturated fatty acids, such as oleic, linoleic, and α-linolenic acids (p < 0.05). Meanwhile, pan-fried and deep-fried meat had higher amounts of VFCs than baked meat. The OPLS-DA similarity and fingerprinting analyses revealed significant differences between the three heat treatment methods. Aldehydes were the key aroma compounds in pan-fried meat. Importantly, 3-methylbutyraldehyde and 2-heptanone contents were positively correlated with eicosenoic, oleic, isooleic, linoleic, α-Linolenic, and eicosadiene acids (p < 0.05). To sum up, pan-fried Black Tibetan sheep meat had the best edible, nutritional, and flavor quality.

To explore the influence of cooking methods on the flavor parameters of Tibetan sheep, various techniques such as atmospheric-pressure (AP), high-pressure (HP), atmospheric-pressure high-pressure (APHP), and high-pressure atmospheric-pressure (HPAP) cooking were tested. The results indicated that APHP and HP cooking yielded the best sensory qualities, accounting for 26.15% and 25.51%, respectively. The HP group had the highest amino acid content at 34%, enhancing the meat’s sweet taste due to alanine, glycine, arginine, and methionine. Among 40 detected fatty acids, the order of saturated fatty acid (SFA), monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), and n-6/n-3 content was AP > APHP > HPAP > HP (p < 0.05). An electronic tongue and nose identified aroma components across the four cooking methods. Similarities in aroma were observed among the samples after cooking, while significant differences were found in the aroma components between the AP group and the other three cooking methods (p < 0.05). The gas chromatography–ion mobility spectrometry (GC–IMS) and gas chromatography–mass spectrometry (GC–MS) analyses of the meat in the four groups indicated that there were significant differences in volatile compounds among meat cooked with different methods (p < 0.05), with 56 and 365 flavor compounds detected by the two analytical techniques, respectively. Moreover, the GC–MS results indicated that the flavor substance content in the HP group accounted for 30.80% among these four sample groups. This comprehensive analysis showed that high-pressure steaming could significantly improve the flavor quality of Tibetan sheep, providing a theoretical basis and empirical reference for the optimization of pre-treatment conditions and the processing of Tibetan sheep.

Substituting traditional protein feed with palm kernel meal (PKM) in the diet of Tibetan sheep can be a cost-effective feeding strategy. To determine the impact of PKM on flavor development in different adipose tissues of Tibetan sheep, subjects were fed with 15% and 18% of PKM, while the control group received no PKM. The fatty acids and volatile compounds in the samples were then analyzed by GC-MS and HS-GC-IMS. Adding PKM to the diet significantly increased the C12:0, C14:0, C16:0 and C18:1N9 content in adipose tissues compared with the control, and most of these were associated with flavor formation (p < 0.05). The flavor compounds in the adipose tissues predominantly consisted of alcohols, ketones, acids and aldehydes. In particular, including PKM in the diet increased the proportion of ketones but decreased the proportion of alcohols, acids and aldehydes in subcutaneous and tail fat. Specifically, the proportion of acetone, acetoin monomer, 2,3-butanedione, 2-butanone monomer, 2-methyl-2-propanol, 2-methyl-2-propanol and methyl acetate increased significantly in the subcutaneous and tail fat (p < 0.05), while that of ethanol, 1-propanol monomer, butanol monomer, acetic acid monomer and acetic acid monomer decreased. Intermuscular fat exhibited variable results, mainly because the addition of PKM resulted in higher proportions of alcohols, including ethanol, 1-propanol and butanol monomer, especially at 15% PKM. In summary, the addition of PKM improved the flavor of Tibetan sheep fat and increased the amount of favorable volatile flavor compounds. This study can serve as reference for understanding the effects of dietary PKM on the adipose tissue flavor profile of Tibetan sheep.

This study aimed to examine the effects of oats cultivated in saline and non-saline environments on the meat quality and muscle metabolism of Qinghai Tibetan sheep. First, targeted and untargeted metabolomics were used to examine oat quality and metabolites. Second, sheep muscle quality and metabolites were analyzed. Finally, a combined examination of the quality of the oats and their metabolites, as well as that of the muscles, was compared with saline oats. This study hypothesizes that, compared with non-saline environments, soil salinization can improve the nutritional quality of oats, thereby enhancing the meat quality and muscle metabolism of Qinghai Tibetan sheep. Saline-grown oats were shown to have higher levels of crude protein, crude fat, free amino acids, and simple sugar. The meat quality of the sheep fed on saline oats was higher due to free amino acid and carbohydrate metabolism, resulting in improved texture, color, water-holding capacity, and cooked meat percentage, with lower steaming loss. The findings of this study confirm the hypothesis that salinization improves Tibetan sheep meat quality by optimizing oat composition, providing a reference for agricultural and animal husbandry production in saline areas.

Castration is a vital technical practice in Tibetan sheep farming on the Qinghai-Tibet Plateau. It reduces fighting among rams, making it easier to manage the herd while they are grazing. However, the impact of castration on the quality of Tibetan sheep meat and muscle metabolites is unclear at present. On this basis, this study examined differences in meat quality and metabolites between castrated (BTC) and non-castrated (BTN) Black Tibetan sheep using targeted and non-targeted metabolomics. Compared with the BTN group, the meat from the BTC group showed reduced drip loss and increased cooking loss, as well as higher levels of elasticity, chewiness and cohesiveness (P < 0.05). The levels of 11 amino acids, total amino acids, total umami amino acids, 23 fatty acids, SFA, PUFA and MUFA were significantly higher in the BTC group than in the BTN group (P < 0.05). A total of 34 differentially abundant metabolites were identified between the two groups, with uric acid, vitamin C, malate, glutamine and oleic acid being all upregulated in BTC. Purine metabolism, metabolic pathways, bile secretion, the phosphotransferase system, glyoxylate and dicarboxylate metabolism, pyrimidine metabolism, and ABC transporters were the key metabolic pathways associated with meat quality in the castrated group. In conclusion, there are certain differences in meat quality and muscle metabolites between BTC and BTN. Castration can affect meat quality characteristics to a certain extent.

Optimizing the dietary nitrogen-to-sulfur (N:S) ratio is crucial for enhancing ruminal microbial fermentation and nutrient digestibility. This study investigated the effects of different dietary N:S ratios on ruminal antioxidant indices, digestive enzyme activities, immune parameters, volatile fatty acid (VFA) profiles, microbial communities, and metabolomic profiles in plateau-type Tibetan sheep. Ninety 2-month-old male Tibetan sheep (initial body weight, 15.55 ± 0.20 kg) were randomly assigned to three dietary treatments formulated with N:S ratios of 9.5:1 (HP-H), 8.5:1 (HP-M), and 7.5:1 (HP-L). Sheep fed the HP-H diet exhibited improved ruminal antioxidant indices compared with the other treatments, with CAT and T-AOC activities being higher than those of both the HP-M and HP-L groups, while SOD and GSH-Px activities were significantly higher only compared with those in the HP-L (p < 0.05). Furthermore, ruminal cellulase activity, as well as propionate and butyrate levels, were significantly higher in the HP-H group (p < 0.05). Microbiome analysis revealed that the HP-H diet enriched the relative abundances of Candidatus Saccharimonas, the Rikenellaceae RC9 gut group, and uncultured rumen bacteria. Correspondingly, untargeted metabolomics identified higher signal intensities of 3-hydroxyphenylacetic acid, nervonic acid, arachidonic acid (peroxide-free), and calciferol in the ruminal fluid of the HP-H group relative to the other treatments. In conclusion, when the nitrogen-to-sulfur ratio was 9.5:1, ruminal antioxidant enzyme activities were increased, and the concentrations of propionic acid and butyric acid were increased. The differential microorganisms and metabolites were mainly associated with lipid metabolism, as well as cofactor and vitamin metabolism.