Roast Tan sheep (an indigenous breed in Yanchi County, Ningxia Hui Autonomous Region) meat adulterated with duck meat and pure roast sheep meat were discriminated by an electronic nose. Their volatile composition was analyzed by headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and chemometrics. The results showed that a total of 53 volatile compounds were identified in five adulterated samples, including 12 alcohols, 15 aldehydes, 3 acids, 2 esters, 8 ketones, 8 alkanes, 1 heterocyclic compound and 4 other compounds. Principal component analysis (PCA) clearly distinguished the electronic nose data for the overall odor of adulterated roast mutton samples, and showed that the major differential volatile compounds were alcohol compounds. By partial least squares discriminant analysis (PLS-DA), five characteristic volatile substances were found in adulterated samples, namely 1-octanol, 1-pentanol, hexanal, acetic acid, and dodecane, which will be useful to determine the level of duck meat in adulterated roast mutton samples.

Moisture distribution and migration in the tallow of Tan sheep from Yanchi, Ningxia roasted for different periods were analyzed by low field-nuclear magnetic resonance (LF-NMR). Head space solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and an electronic nose (E-Nose) were used to analyze the volatile components of mutton tallow. The results showed that the L^* value of mutton tallow decreased, and the a^* and b^* values increased with roasting time. The percentage of weakly bound water showed an increasing trend, and the percentage of immobile water showed a decreasing trend. The relaxation time T₂₃ showed a significantly decreasing trend with roasting time, indicating tighter binding of water molecules to macromolecular substances. A total of 78 volatile compounds were detected in 10 samples, including 12 aldehydes, 11 alcohols, 9 ketones, 4 alkanes, 10 acids, 12 esters, 12 heterocyclic compounds and 8 other compounds, with hexanal, nonanal, 1-octene-3-ol, 3-hydroxy-2-butanone, 7-methyl-3-methylene-1,6-octadiene and toluene being the major ones. Esters were found mainly in the early stage of roasting, while heterocyclic compounds, especially pyrazine compounds, mainly in the late stage. Principal component analysis performed on E-nose data showed that different roasting periods had significant effects on the contents of nitrogen oxides, benzenes, organic sulfur compounds and alcohols in mutton tallow, but little effect on alkanes, hydrides and ammonia compounds.

The moisture distribution and key volatile flavor compounds of beef tallow from Qinchuan cattle roasted for different periods were analyzed by low field-nuclear magnetic resonance (LF-NMR) spectroscopy and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that the L* value significantly decreased (P < 0.05), the a* and b* values first increased and then decreased with roasting time. The proportion of bound water in beef tallow did not change significantly (P > 0.05), while the proportion of immobile water first increased and then decreased, and the proportion of free water showed an overall downward trend (P > 0.05). The relaxation time T₂₃ and T₂₄ showed a significant decreasing trend as roasting time increased (P < 0.05), indicating that the binding between water molecules and macromolecular substances such as protein and lipid became tighter. Beef tallow samples roasted for different periods could be effectively distinguished by electronic nose and the roasting process had a significant effect on the contents of alcohols, aromatic compounds, terpenes, and organic sulfur compounds in beef tallow according to principal component analysis (PCA) of the electronic nose data. A total of 95 volatile compounds were identified in all samples. The contents of 1-methoxy-2-propanol, 1-octene-3-ol, hexanal, nonanal, acetic acid, nonanoic acid, and acetamide were relatively higher in each sample, whereas ketones, heterocycles and amine compounds occurred mostly in the later stages of roasting. In total 19 key aroma components were identified based on odor activity value (OAV) and most of the substances have the largest OAV at 12 min of roasting.

The dynamic changes of key volatile compounds and water distribution in the pig skin jelly with different NaCl addition (0.0%, 0.5%, 1.0%, 2.0%, and 4.0%) were identified and analyzed. A total of 28 volatile compounds were identified in all samples of pig skin jelly. Compared with the sample without NaCl addition, aldehydes, alcohols and ketones were significantly increased in the pig skin jelly with NaCl addition. In addition, 12 key volatile flavor compounds, including hexanal, nonanal, octanal, (E,E)-2,4-decadienal, (E,Z)-2,6-nonadienal, (E)-2-nonenal, (E)-2-heptenal, (E)-2-octenal, 1-hexanol, 2-ethyl-1-hexanol, 1-octen-3-ol and 2,3-octanedione were further identified. With the increase of NaCl concentration, the free water located in the intercellular space was transformed into immobilized water entrapped in the myofibrillar network, increasing the water-holding capacity of pig skin jelly. Correlation analysis showed that T₂₁ had strong negative correlations with (E)-2-nonenal and 1-hexanol, T₂₂ had strong negative correlation with (E,E)-2,4-decadienal, and positive with (E,Z)-2,6-nonadienal and (E)-2-heptenol, and T₂₃ had strong negative correlations with (E,Z)-2,6-nonadienal and (E)-2-heptenol. In conclusion, this study provides a reference for the utilization of pig by-product and salt reduction of Chinese meat products.