## 3 Results
### Volatile Flavor Compounds  
The number of aldehydes identified in the G12, G8, G4, G2, and G0 groups was 12, 12, 11, 9, and 9, respectively (Table 6). The content of pentanal, hexanal, heptanal, 2-octenal, and 2-nonanal in the G0 group were significantly higher than in other groups (\(p<0.05\)), but no differences were evident among the G12, G8, G4, and G2 groups (\(p>0.05\)). Benzaldehyde had a higher concentration in the G0, G12, G8, and G4 groups than in the G2 group (\(p<0.05\)). Tetradecanal was higher in the G12 group than in the G8 and G4 groups (\(p<0.05\)) but was not detected in the G2 and G0 groups. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Items**} & \multicolumn{4}{c}{**Treatments**} & \multirow{2}{*}{**Odor Descriptors**} \\ \cline{2-2} \cline{4-6}  & **G12** & **G8** & **G4** & **G2** & **G0** \\ \hline Pentanal & 2.13 \(\pm\) 0.14 b  & 2.25 \(\pm\) 0.21 b  & 1.93 \(\pm\) 0.10 b  & 1.91 \(\pm\) 0.16 b  & 5.35 \(\pm\) 0.23 a  & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ Hexanal & 9.59 \(\pm\) 0.45 b  & 10.51 \(\pm\) 1.04 b  & 10.35 \(\pm\) 0.99 b  & 7.25 \(\pm\) 0.68 b  & 47.19 \(\pm\) 3.12 a  & Herbal, grassy \\ Heptanal & 8.73 \(\pm\) 0.52 c  & 12.17 \(\pm\) 0.88 b  & 7.50 \(\pm\) 0.46 c  & 7.56 \(\pm\) 0.51 c  & 23.63 \(\pm\) 1.39 a  & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ Octanal & 19.83 \(\pm\) 0.97 b  & 14.42 \(\pm\) 1.01 c  & 21.94 \(\pm\) 1.61 ab  & 9.34 \(\pm\) 0.85 d  & 26.58 \(\pm\) 2.68 a  & Citrus, floral \\ Nonanal & 23.84 \(\pm\) 3.19 & 26.13 \(\pm\) 2.86 & 33.24 \(\pm\) 2.07 & 36.23 \(\pm\) 3.98 & 26.58 \(\pm\) 3.74 & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ Benzaldehyde & 46.97 \(\pm\) 2.86 ab  & 54.50 \(\pm\) 4.78 ab  & 42.23 \(\pm\) 3.98 b  & 25.77 \(\pm\) 2.86 c  & 59.27 \(\pm\) 4.17 a  & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\
2-ethylhexanal & & 1.05 \(\pm\) 0.42 & 2.31 \(\pm\) 0.10 & 3.01 \(\pm\) 0.69 & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\
2-octenal & 2.15 \(\pm\) 0.02 b  & 1.96 \(\pm\) 0.01 b  & 1.82 \(\pm\) 0.02 b  & 2.04 \(\pm\) 0.03 b  & 4.65 \(\pm\) 0.31 a  & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ Decanal & 2.05 \(\pm\) 0.10 & 2.05 \(\pm\) 0.24 & 4.29 \(\pm\) 0.79 & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ Hexadecaldehyde & 2.72 \(\pm\) 0.12 & 2.98 \(\pm\) 0.17 & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\ Tetradecanal & 3.29 \(\pm\) 0.20 a  & 1.55 \(\pm\) 0.10 b  & 1.76 \(\pm\) 0.05 b  & & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\
2-nonenal & 2.12 \(\pm\) 0.07 b  & 1.80 \(\pm\) 0.08 b  & 2.00 \(\pm\) 0.05 b  & 1.88 \(\pm\) 0.05 b  & 4.95 \(\pm\) 0.16 a  & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} \\
2,4-decaional & 1.48 \(\pm\) 0.07 & 1.58 \(\pm\) 0.04 & & & & \\ \hline \end{tabular} Different superscripts (a and b) mean significant differences (\(p<0.05\)). The values are the means \(\pm\) SE (\(n=10\) per group). G12, G8, G4, and G2 mean that the lamb grazing time was 12 h, 8, 4 b, and 2 h per day, respectively. G0 means indoor supplementary feeding.  
\end{table} 
Table 5: PH, meat color, and cooking loss of \(LT\) muscle of Tan lambs under different restricted grazing time and indoor supplementary feeding systems. The content of alcohols was affected by different grazing time and indoor feeding systems (Table 7). There were seven alcohols detected in both the G12 and G8 groups, and 6, 5, and 3 alcohols were identified in the G4, G2, and G0 groups, respectively. Menthol content was higher in the G12 group than in the G8, G4, and G2 groups (_p_ < 0.05) but was not detected in the G0 group. The contents of 1-octene-3-ol and 2-octenol were significantly higher in the G12 and G8 groups than in the G0 group (_p_ < 0.05). Decanol was found in the G12, G8, G4, and G2 groups but was absent in the G0 group. Table 8 shows the ketones, esters, and heterocyclic compounds of _LT_ muscle affected by restricted grazing time systems in Tan lamb.