## 3 Results
### Volatile Compounds and Microbiological Spoilage in Spanish Chorizo
#### 3.2.1 Volatile Compounds  
The obtained results of volatile fatty acids analysis by GS-MS are shown in Table 4.  
Volatile compounds from lipid oxidation (propan-2-ol, hexanal, and nonanal) were significantly affected (\(p<0.05\)) by the ripening time and addition of antioxidants (Table 3). In contrast, octet-2-ol was not affected by the ripening time or addition of antioxidants. In general, 2-propanol increased from 0.45 to 1.75 mg/g meat during 125 days area units to \(316\times 106\) area units during the first 4 days. In contrast, the increase in samples with natural extracts was less pronounced, especially R\({}_{\text{LAW}}\) with a value of 0.85 mg/g at day 150. The production of octet-2-ol was not detected in any of the samples, suggesting good product sensory quality because these compounds have a low threshold off-odour. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Volatile Compounds** & **Sample** & **Day 0** & **Day 25** & **Day 50** & **Day 125** \\ \hline \multirow{7}{*}{propan-2-ol} & Control & \(0.45\pm 0.02\) & \(0.54\pm 0.02\) & \(1.02\pm 0.01\) a  & \(1.75\pm 0.03\) a  \\  & R\({}_{\text{LAW}}\) & \(0.37\pm 0.01\) & \(0.46\pm 0.01\) & \(0.37\pm 0.02\) b  & \(0.85\pm 0.04\) c  \\  & R\({}_{\text{SCe}}\) & \(0.38\pm 0.03\) & \(0.44\pm 0.02\) & \(0.92\pm 0.01\) b  & \(1.10\pm 0.05\) b  \\  & R\({}_{\text{ChB}}\) & \(0.58\pm 0.02\) & \(0.65\pm 0.01\) & \(0.66\pm 0.02\) b  & \(1.27\pm 0.01\) b  \\  & C\({}_{\text{LAW}}\) & \(0.65\pm 0.01\) & \(0.70\pm 0.01\) & \(0.89\pm 0.03\) b  & \(1.20\pm 0.02\) b  \\  & C\({}_{\text{SCe}}\) & \(0.61\pm 0.03\) & \(0.69\pm 0.03\) & \(0.59\pm 0.01\) b  & \(1.33\pm 0.00\) b  \\  & C\({}_{\text{ChB}}\) & \(0.38\pm 0.02\) & \(0.50\pm 0.02\) & \(0.55\pm 0.01\) b  & \(1.08\pm 0.01\) b  \\ \hline \multirow{7}{*}{octen-2-ol} & Control & \(0.11\pm 0.01\) & \(0.10\pm 0.00\) & \(0.15\pm 0.01\) & \(0.10\pm 0.01\) \\  & R\({}_{\text{LAW}}\) & \(0.10\pm 0.02\) & \(0.18\pm 0.02\) & \(0.15\pm 0.02\) & \(0.15\pm 0.02\) \\  & R\({}_{\text{SCe}}\) & \(0.14\pm  
The behaviour of nonanal and hexanal was quite similar, with both increasing during storage and showing significant differences between the control and samples with extracts from day 50 onwards. Nonanal is associated with waxy and painter descriptors, while 1-octen-3-ol is amongst the compounds responsible for rancid odours and it is an autoxidation indicator of linoleic and arachidonic acids. In addition, hexanal is an aldehyde that can be generated from arachidonic acids, oleic acid, and through the degradation of deca-2,4-dienal [28]. Volatile alcohols, such as heptanol, are formed from oleic acid [29], whereas pentanol and 1-octen-3-ol are by-products of the autoxidation of linoleic and arachidonic acids [30]. Hexanal concentration ranging from 2 to 7 g kg\({}^{-1}\) was reported in cooked pork [31] cooked turkey [32] and cooked ground beef [33; 34]. The addition of antioxidants decreased the total volatile compounds from lipid oxidation (2-propanol, hexanal, and nonanal). At the end of process, hexanal contents were found in the following order: C, R\({}_{\text{LAW}}\), R\({}_{\text{SCe}}\), C\({}_{\text{LAW}}\), R\({}_{\text{ChB}}\), C\({}_{\text{SCe}}\), and C\({}_{\text{ChB}}\) and their mean values were 0.44, 0.18, 0.19, 0.19, 0.20, 0.21, and 0.25 mg/g, respectively. These results indicated that the addition of R and Ct improved the control of lipid oxidation compared to the control sample. These results are consistent with the polyphenol content and the in vitro evaluation of the antioxidant activity of the extracts (Table 3). According to [PERSON] [28], all volatile compounds analysed (hexanal, heptanal, octet-2-ol, and propan-2-ol) are components that contribute the most to the emergence of unpleasant notes of flavour due to their high rate of formation and low flavour threshold [35]. The loss of acceptance depends to a large extent on odour and flavour deterioration in meat and meat products [36]. In general, the volatile profile of chorizo strongly depends on the composition.