## 3 Results and Discussion
### Volatile Organic Compounds
A.B Different letters represent a significant difference between fresh and Frozen-Thawed meat within the same breed (\(p<0.05\)). \({}^{\text{-}}\)C Different letters represent a significant difference between the fresh or Frozen-Thawed meat of different chicken breeds (\(p<0.05\)). LRI, Linear retention index. In addition, the results of this study revealed different trends of changes in other VOC contents after freezing between CB and KNC. The concentrations of ketones, 2-pentylfuran (green bean, butter), and octanoic acid (cheesy, sweat, vegetable, waxy, fatty) were higher in fresh CB and lower in Frozen-Thawed KNC meat (\(p<0.05\)). Nevertheless, despite these differences, the freezing process affected VOC content in Frozen-Thawed chicken thigh meat, regardless of the chicken breed. The hydrocarbons D-limonene (mint, lemon, citrus, orange, fresh, sweet), heptadecane (alkane), hexadecane (alkane), naphthalene (dry, pungent, tarry, tarry), pentadecane, 3-methyl- (alkane), and tridecane (alkane); the esters arsenous acid,  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & & \multicolumn{2}{c}{**Broiler**} & \multicolumn{2}{c}{**HH3**} & \multicolumn{2}{c}{**WRMD1**} & \multicolumn{2}{c}{**WRMD2**} \\ \cline{3-10}
**VOCs** & **m/z** & **LRI** & \multicolumn{2}{c}{**Fresh**} & \multicolumn{2}{c}{**Frozen-Thawed**} & \multicolumn{2}{c}{**Fresh**} & \multicolumn{2}{c}{**Frozen-Thawed**} & \multicolumn{2}{c}{**Fresh**} & \multicolumn{2}{c}{**Frozen-Thawed**} \\ \hline Heptadecane & 57 & 1702 & 0.048 \({}^{\text{A}}\) & 0.000 \({}^{\text{B}}\) & 0.053 \({}^{\text{A}}\) & 0.000 \({}^{\text{B}}\) & 0.055 \({}^{\text{A}}\) & 0.000 \({}^{\text{B}  
tris(trimethylsilyl) ester (odorless), decanoic acid, ethyl ester (apple, brandy, waxy, grape, oily, sweet, fruity, pear), hexadecanoic acid, and ethyl ester (Asian pear, blackberry, break-fast cereal, coriander); the ketones 5,9-undecadien-2-one and 6,10-dimethyl- (odorless); the alcohols 1-hexanol and 2-ethyl-alcohol (odorless); and the aldehydes pentadecanal (fresh, waxy), tetradecanal (citrus peel, incense, amber, waxy, fatty), and tridecanal (grapefruit peel, citrus, must, fresh, waxy, sweet) aldehydes were present in lower (\(p<0.05\)) concentrations in Frozen-Thawed meat than in fresh meat. The results were in line with those of [PERSON] et al. [13], who mentioned that as the development of VOCs are mainly due to PUFAs, which have a lower rate of stability compared to both MUFAs and SFAs, lipolysis of phospholipids occurs during the frozen storage of meat, and is assumed to be the main factor for the intensification of aroma-active compounds, which was also observed in this study. However, regardless of the chicken breed, the contents of certain VOCs were decreased or even lost in Frozen-Thawed meat. Pentadecane (alkane), tetradecane (alkane, mild, waxy), dodecane, 2,6,11-trimethyl- (alkane), 4,6-dimethyl- (alkane), n-hexane (alkane), and 2,4-dimethyldodecane (odorless) hydrocarbons were lost in Frozen-Thawed meat, and the concentrations of n-hexane, benzene, and 1,3-bis(1,1-dimethylethyl)- were lower (\(p<0.05\)) in Frozen-Thawed meat from all KNC breeds, especially HH3 and WRMD2. Butylated hydroxytoluene (odorless) ester, 1-hexanol, and 2-ethyl-alcohol (odorless) were also affected by the freezing process, and their concentrations were decreased (\(p<0.05\)) in Frozen-Thawed thigh meat from KNC breeds. [PERSON] et al. [13] revealed lipid degradation as a main factor in the development of VOCs, and heating and storage are believed to be important contributors to this process. Most VOCs in meat are derived from PUFAs, particularly oleic and linoleic acids. During oxidation, the unsaturated bonds of PUFAs, which are vulnerable under stress conditions, will induce the formation of most major VOCs, such as octanal, hexanal, heptanal, and nonanal [55]. Hexanal may further react to generate 4,5-dimethyl-2-pentyl-3-oxazoline, which produces an unfavorable aroma perception, whereas nonanal contributes to the meaty aroma when converted into 12-methylridlecanal [56].