## 3 Results and Discussion  
### GC-MS/MS Analysis of Volatile Compounds in Lamb Patties  
The results of volatile compounds from the GC-MS/MS analysis are shown in Figure 1 in a heat map. Volatile organic compounds are formed through lipid oxidation, Strecker degradation or Maillard reaction [23], which are accountable for the development of meat flavour. The results of our study show the presence of 39 volatile compounds in lamb patties. 2,3-octadione is the compound most present with 20.43-27.83 \(\upmu\)g/g in all the different cooking methods. Superheated steam had the highest content of this compound. 1-hexanol was 7.02-34.74 \(\upmu\)g/g in all cooked samples. Charcoal-grilled samples had the highest content of 1-hexanol. 1-octen-3-ol was highest in superheated-steam patties with 35.83 \(\upmu\)g/g, while in the charcoal-grilled sample, the content was 26.51 \(\upmu\)g/g. Although the final temperature of the interior of the meat samples in all methods was 72 \({}^{\circ}\)C, the time courses of the temperature in the four cooking methods were not recorded. The temperature in the interior of the meat samples could have increased at different rates  
Figure 1: Heat map of total volatile compounds present in lamb patties cooked by four cooking methods. The abbreviations indicate CRR for charcoal-grilled, EBR for electric-barbecue-grilled, IR for infrared-grilled and SHR for superheated-steam-roasted. because of different heat transfer among cooking treatments. This could have influenced the odour and flavour of the lamb. The meat volatile profile is dependent on many factors, the most important being the cooking procedureMoreover, Ref. [24] suggested that 2,3-octanedione may be a biomarker for animals feeding on pastures. In this way, that compound helps to confirm the origin of the lamb meat. It has been observed that the increase in cooking temperatures enhances the rate of chemical reactions producing compounds that provide the characteristic lamb aroma, this being the most relevant sensory quality for acceptance by lamb consumers. Ketones appear in large amounts in food and seem to have a great influence on the aroma giving a peculiar odour to meat and meat products [25]. However, it has recently been pointed out by [15] that some lipid-oxidation-derived volatiles and TBARSs increased while cooked-meat aroma compounds were reduced. According to [26], 2,3-octanedione can be considered as one of the important compounds distinguishing stir-frying stages. This compound has also been related to undesirable changes during meat product ripening due to microbial metabolism reactions [27]. However, meat from the present study was not aged; therefore the presence of 2,3 octanedione is more attributed to the cooking rather than to the ripening of meat. However, aldehydes appear to be more important to ketones among the volatiles in meat. Ref. [28] observed that the detectable volatile components in cooked meat are mostly generated from the oxidation of fat and volatile component production as they are affected by the cooking temperature and are greater for aldehydes (octanal, nonanal, benzaldehyde and hexanal) than for hydrocarbons (3-methylnonane, toluene, decan, benzene and hexane) and ketones. On the other hand, it has been reported that 4-nonanol, 1-dodecanol, 1-hexanol, 1-pentanol and all long-straight-chain alcohols may contribute to miso product aroma with a lower threshold value [29]. In addition to that, branched-chain alcohols, such as 1-nonen-3-ol, (E)-2-octen-1-ol and 1-octen-3-ol, could participate in the aroma of the mutton dish sao zi as they also have low threshold values [26]. Aliphatic compounds might provide aroma to the meat flavour through unsaturated alcohols that have threshold values lower than those of saturated alcohols [29; 30; 31]. Meat proteins, which contain iron haemoglobin and myoglobin, are denatured during cooking liberating free iron which is a major oxidative catalyst in the meat, and endogenous antioxidant mechanisms of muscle are inactivated [32].