## 3 Results and Discussion
### Hr \({}^{1}\)H NMR Case Study: Time-Dependent Tracking of Aldehyde LOPs in CFOs Exposed to LSSFEs
Figure 1: _Cont._  
Figure 1: (**a**) Expanded aldehyde-CHO proton (9.35–10.20 ppm) region of 600 MHz \({}^{1}\)H NMR spectra of a typical conidia oil product exposed to thermal stressing episodes at 180 \({}^{\circ}\)C for periods of 0–90 min according to our LSSFEs (samples were collected for \({}^{1}\)H NMR analysis at the 0 (unheated), 5, 10, 20, 30, 60 and 90 min time-points). (**b**,**c**), Corresponding 400 MHz \({}^{1}\)H NMR spectral regions of commercially available UK brands of com and sunflower oils, respectively, heated under the same conditions for only 0, 5 and 10 min. All resonances visible are doublets (\(J\) = 7.63 Hz for _trans_-2-alkenals), with the exception of the \(n\)-alkanal one which is a triplet (\(J\) = 1.83 Hz). Assignments for these signals were confirmed via the acquisition of corresponding one- and two-dimensional correlation (COSY) and total correlation (TOCSY) spectra for each heated oil as described in [12; 19; 20]. Detectable aldehyde levels for the unheated (time-point = 0 min) corn and sunflower oil samples are notable. Abbreviations: 1, _trans_-2-alkenals (doublet); 2, alka-(_trans_)-2,4-dienals (doublet); 3,4,5-Epoxy-_trans_-2-alkenals (doublet); 4,4-hydroxy-/4-hydroperoxy-_trans_-2-alkenals (overlapping doublets); 5, alka-(_cis_,_trans_)-2,4-dienals (doublet); 6, higher homologue \(n\)-alkanals (triplet); 7, low-molecular-mass \(n\)-alkanals (triplet) such as ethanol and propanal, which predominantly arise from the peroxidation of linolenoylglycerol substrates available in soybean oil (up to 9.5% (\(w/w\))); ethanol is also generated from the thermal degradation of deca-2,4-dienals [13]); 8, _cis_-2-alkenals (doublet); 9, unidentified aldehyde, presumably a substituted _cis_-2-alkenal species. Figure 2: Cont. Figure 2: _Cont._  
Figure 2: Cont. Figure 2: _Cont._  
The mean concentration magnitude orders of aldehyde generation at typical shallow-frying sampling time-points of only 10 and 20 min (the latter commonly employed for the frying of chicken strips, for example) were found to be sunflower \(>>>\) canola \(\approx\) extra-virgin \(\approx\) coconut oils (non-\({}^{1}\)H NMR detectable in the latter three), and sunflower \(>\) canola \(>\) extra-virgin olive \(\approx\) coconut oils (undetectable in the latter two), respectively, for _trans_-2-alkenals; sunflower \(>\) extra-virgin olive \(>\) canola \(\approx\) coconut oils (undetectable in the latter two), and sunflower \(>\) extra-virgin olive \(>\) canola \(>\) coconut oils (undetectable in the latter medium only), respectively, for _n_-alkanals. However, for peroxididsised linoleicoylglycerol-derived alka-(_trans,trans_)-2,4-dienals, these orders were sunflower \(>>\) extra-virgin olive \(>\) canola \(\approx\) coconut oils (undetectable in the latter two), and SFO \(>>\) canola \(>\) extra-virgin olive \(>\) coconut oils (undetectable in the latter oil only). At the 5 min shallow frying-simulated time  
Figure 2: Boxplots of median\(\pm\)95% confidence intervals (CIs) levels of \({}^{1}\)H NMR-determined _trans_-2-alkenals, alka-(_trans,trans_)-2,4-dienals and _n_-alkanals generated in (**a**) sunflower, (**b**) extra-virgin olive, (**c**) canola and (**d**) coconut oils at 0, 5, 10, 20, 30, 60 and 90 min time-points of exposure to LSSFEs at a temperature of 180 \({}^{\circ}\)C. The notch depicts the median CIs, and the mean concentrations of each group are indicated by yellow diamonds. Abscissa and ordinate axes are heating time-points and aldehyde concentrations (mmol kg\({}^{-1}\)), respectively. (**e**–**g**), Corresponding cubic spline polynomial plots of mean total \({}^{1}\)H NMR-determined _trans_-2-alkenal, alka-(_trans_)-2,4-dienal and _n_-alkanal concentrations, respectively, as a function of heating time for coconut (blue), canola (red), extra-virgin olive (green) and sunflower (yellow curve) oils.