## 3 Results and Discussion
### Volatile Analysis of Lamb Patties by E-Nose  
An e-nose was used to assess the samples for distinguishing flavour based on information from a volatile analysis. PCA was used to analyse the e-nose data obtained from the cooked meat samples (Figure 2). The values for PCA were calculated from the data of sensors in the e-nose. From the analysis by the e-nose, it was observed that the first component PC1 showed 56.26% of variance, the second component PC2 showed 17.45% of variance, and the total variance was 73.71%. Figure 2 shows that there was a strong association between the e-nose volatile compound profile and the cooking method. This gives evidence that the volatile compounds generated by the patty cooking are closely related to the method of cooking. The results of the correspondence analysis show that the strongest correspondence to the volatile compound category was that of the electric-barbecue-grilled (EBR) and the infrared-grilled (IR). The discriminant analysis (Table 1) showed that all cooking types had good discrimination (\(p<0.05\)) between each other with the exception of charcoal-grilled and electric-barbecue-grilled samples of lamb patties where discriminant values were not significant (\(p>0.05\)). These two cooking methods are also in the same part of PC1 which could mean that both of them distinguish or explain equally the e-nose volatile compounds. Figure 2: Principal component analysis score projection of e-nose volatile analysis of charcoal-grilled, electric barbecue-grilled, infrared grilled and superheated-steam-roasted lamb patties. The abbreviations indicate CRR for charcoal grilled, EBR for electric barbecue grilled, IR for infrared-grilled and SHR for superheated-steam-roasted. In a study by [45], a PCA analysis showed that the cumulative variance was 97.90%. Both PC1 and PC2 helped to distinguish the flavour profile of the mutton that was processed. The results show that there existed a correlation among the flavour components within the samples based on the volatile compound distinction. The content and nature of the volatile organic compounds (VOCs) that develop after cooking are influenced by genetic (sex, selection, breed, species) factors, meat processing, feeding and animal management and product storage. Different breeds of sheep or lamb also have an impact on different volatile compound formation while cooking. The ability of the e-nose in differentiating volatiles released from cooked lamb meat samples by different methods was evaluated using discrimination power values derived from pairwise PCA analysis (Table 1). Discrimination power was expressed as a decimal fraction of the proportion of principle component identification of the lamb patties' elements that were identified and determined to be different among cooking methods. Table 1 shows that among the four cooking methods, the most significant difference (\(p\) < 0.05) was observed between electric-barbecue and superheated-steam-roasted samples. Lipid oxidation is also an important process that enhances the development of volatile compounds. As a result, about 50% of volatile components generated are lipid oxidation products. The volatile compounds identified in the present study agree with the volatile profiles reported for lamb fat and low-temperature (<90 \({}^{\circ}\)C) heated meat [14]. Few cyclic compounds were formed such as alkenes that indicate a stronger heat treatment. Therefore, higher heat generation will produce higher amounts of cyclic compounds. Cooking at high temperatures leads to oxygen discharge and hence production of iron inducing free radicals. Therefore, cooked meats are even more susceptible to lipid oxidation than raw meat. In addition, cooking also stimulates the release of non-heme iron from pigments as a result of the phospholipid exposition to oxygen. The increase of non-heme iron release is faster in slow heating than fast heating. Reduction of breakdown of hydroperoxide into free radicals and lower activation energy for oxidation have been associated with high-temperature cooking [46].