## 3 Results and Discussion
### Volatile Analysis
#### 3.3.3 Frozen Samples  
In terms of PEF treated frozen samples, n-3, C18:3 (n-3), PUFA, n-6, C18:2 (n-6), C20:3 (n-6), C20:2 (n-6), C18:0, C20:5 (n-3), SFA, and C20:1 (n-9) fatty acids had VIP scores of \(>\) 1 indicating that they are the most important variables in relation to sensory perception (Figure 5e; Supplementary Tables S6 and S7). [PERSON] et al. [29] attributed the increase in flavour of frozen _longissimus lumbarum_ lamb muscles to the increase in PUFA content, especially n-3 PUFA content. This is because PUFAs are generally more prone to oxidative degeneration, which results in the production of volatile flavour compounds in meat. Moreover, [PERSON] et al. [30] reported that n-3 PUFA, mainly C18:3 (n-3) (a-linoleic acid) showed the strongest positive correlation with lamb flavour. [PERSON] et al. [31] also found that when concentration of C18:3 (n-3) fatty acid increased, the score for lamb flavour intensity and flavour liking significantly increased. Among the amino acids, ornithine, aspartic acid, serine, phenylalanine, histidine, glycine, threonine, and isoleucine amino acids were the important contributors (VIP \(>\) 1) to the sensory perception of PEF treated frozen lamb samples (Figure 5f). The presence of free amino acids like phenylalanine, isoleucine, threonine, and serine in the frozen samples of lamb can contribute to brown/roasted attribute, which is desired by consumers [21]. Free amino acids like isoleucine and phenylalanine contributed to the flavour of frozen beef loins [32]. Moreover, glycine, aspartic acid, alanine, phenylalanine, tyrosine, and glutamic acid have been collectively called as flavour amino acid (FAA) because of their contribution to the flavour and freshness in imported and local chicken breast, beef, and Nile tilapia fish frozen at \(-7\,^{\circ}\)C for 1 month and \(-18\,^{\circ}\)C for 3 and 6 months [33]. Flavour volatiles that contributed to the overall sensory perception of PEF treated frozen lamb samples included 2-ethylfuran, dimethyl disulphide, 2-nonanone, pyridine, 2,5-dimethyl-3-ethyl pyrazine, heptanal, 2-ethyl-3-methyl pyrazine, 3,5-diethyl-2-methyl pyrazine, 2-pentylfuran, 2-heptanone, dimethyl trisulphide, and 2-furanmethanethiol, 3-methylbutanal (VIP \(>\) 1) (Figure 5g). Sulphur compounds like dimethyl sulphide and dimethyl trisulphide significantly contributed to the aroma of pork (frozen at \(-80\,^{\circ}\)C), and this was attributed to their high reactivity as they can either react with each other or with other compounds, leading to the production of more complex aroma compounds [34]. In addition, pyrazines that generally result from the Maillard reaction and Strecker degradation also produced important flavour volatiles for PEF-treated frozen samples. [PERSON] et al. [35] reported that Irish beef frozen at \(-20\,^{\circ}\)C had the highest concentration of pyrazines, which contributed to roasted beef flavour of Irish beef. In contrast to chilled samples, ketones were one of the highest contributors to flavour of PEF treated frozen lamb. [PERSON] et al. [36] identified 2-nonanone, a methyl ketone, as one of the most important compounds in defining the flavour of lamb/mutton. When considered together, the most important components that contributed to the overall sensory flavour perception of frozen samples were fatty acids (n-3, C18:3 (n-3), PUFA, n-6, C20:3 (n-6), C18:2 (n-6), C20:2 (n-6), C18:0, C20:5 (n-3), SFA, C20:1 (n-9),MUFA, C18:1 cis-9), flavour volatiles (2-nonanone, 2-ethyl-3-methyl pyrazine, 2-ethylfuran, dimethyl disulphide, 2,5-dimethyl-3-ethyl pyrazine, pyridine, heptanal, 3,5-diethyl-2-methyl pyrazine), and amino acids (ornithine, serine, aspartic acid, phenylalanine, histidine, threonine, isoleucine and glycine) (Figure 5h). Fatty acids predicted the sensory perception of PEF treated frozen samples better compared to chilled samples.