## 3 Results and Discussion
### Case Study Review: Analytical Advantages Offered by \({}^{1}\)H NMR Analysis of LOPs in CFOs  
Results acquired clearly demonstrated that the heating of UK-available seed and further vegetable culinary oil products according to shallow frying practices generates very high levels of extremely toxic aldehyde LOPs, which arise from the thermally stimulated, O\({}_{2}\)-boosted peroxidation of PUFAs and MUFAs therein; these toxins have been proven to be absorbed from the gut into the systemic circulation following their dietary ingestion [23]. As expected, higher levels of toxic aldehydes are generated in oils rich in the more readily peroxididisable PUFAs, although significant amounts also arise from MUFAs at prolonged heating times (i.e., after one or more significant lag phases). Moreover, only two major classes of aldehydes are produced from the fragmentation of MUFA-derived HPMs (specifically \(n\)-alkanals and _trans_-2-alkenals, the former of which are arguably of a lower toxicity than the latter), whereas a much broader pattern of these agents are produced from PUFA-derived CHPD fragmentation, for example 4,5-epoxy-_trans_-2-alkenals and alka-(_trans_,_trans_)-2,4-dienals [14; 17]), all of which have the potential to exert a very high level of adverse health effects in humans. Intriguingly, the total unsaturated aldehyde concentration determined in PUFA-rich corn or sunflower oils heated for a period of 90 min according to our LSSFEs is very close to 50 mmol kg\({}^{-1}\), an extremely high level indeed. This investigation also demonstrates that high-resolution \({}^{1}\)H NMR analysis offers many advantages regarding evaluations of the peroxididative sensitivities of commercially available frying oil products when exposed to LSSFEs, or real-life domestic or commercial frying practices. Moreover, as notable from Figure 1b,c, it is also of value for determining the stabilities and oxidative resistivities of such oils when exposed to long-term storage episodes at ambient or lower temperatures. This multicomponent analytical technique provides a range of benefits over the established accelerated, heat-dependent Rancimat(r) method [58], since it provides valuable molecular information on the identities of a variety of LOP classifications (for example, HPMs, CHPDs, isomeric fatty acid epoxides, and up to 10 classes of aldehyde fragmentation products, and all of these within a single \({}^{1}\)H NMR  
Figure 5: (**a**,**b**), Comparative aldehyde-CHO proton regions of the 60 and 400 MHz \({}^{1}\)H NMR spectra, respectively, of soybean oil heated at 180 \({}^{\circ}\)C for 90 min according to LSSFEs. (**c**,**d**), as (**a**,**b**), respectively, but for a sample of SFA- and MUFA-rich pork lard. The acylglycerol terminal-CH\({}_{3}\) function signals in the 400 MHz spectra acquired revealed that the omega-3 FA content of the soybean oil sample decreased from 9.28 to 8.54 molar % following LSSFE exposure for 90 min. Abbreviations: as Figure 1.  
acquisition which takes ca. 10-15 min). Therefore, this analytical strategy has the ability to support mechanistic investigations of CO UFA peroxidation and/or thermal degradation processes. Hence, NMR analysis enables the rapid, simultaneous, virtually non-invasive, and non-destructive identification and quantification of many major and minor agents that are present in complex, multicomponent CFO samples. Although FTIR analysis, which is now viewed as a 'green' analytical technology [59], is more bench- and sample source-accessible than high-resolution NMR analysis, and may be employed for chemometric determinations of cod liver oil product authenticities [60], and their peroxidation status [61], recent technological developments in the operation of non-stationary, near-portable LF benchtop NMR instruments for such culinary oil analysis purposes, as documented here, now provide considerable analytical advantages [62]. Indeed, these facilities have a much improved molecular selectivity, and in at least some cases specificity, over those offered by FTIR techniques.