## 3 Results
### Volatile Compounds
Thus, aldehydes accounted for 60% of the total area reported in coconut cooked samples. This sharp increment in volatile aldehydes agreed with that reported by [PERSON] et al. [26] in this oil when heated above its smoking point (175\({}^{\circ}\)), suggesting that this oil should not be used for deep-fat frying. Moreover, this increment in aldehydes is related to the values observed for PV and TBARs, which showed significant changes in cooked samples for this oil. However, results found during accelerated storage pointed out a slight degree of oxidation, with increments of mostly aldehydes, that accounted for 30-45% of the total area in T1 and T2 samples, respectively. It was interesting to note, contrary to what was observed in the other two oils, the high amounts of octanoic and hexanoic acids, which are characterized by their \"fatty\" flavor. These fatty acids have also been previously reported in virgin coconut oil treated by different non-thermal processing methods [50]. Grape seed oil, and especially rapeseed oil, showed much more appreciable amounts of volatile compounds in unheated samples as compared to coconut oil. In both cases, the aldehydes family was the predominant one, accounting for approximately 65% (grape seed) 75% (rapeseed) of the total area, with hexanal as the major compound, followed by (E,E)-2,4-heptadien in rapeseed oil and (E)-2-heptenal in grape seed oil. The higher amount of aldehydes in rapeseed oil was in agreement with the highest values found for TBARs in these samples. High values of aldehydes (hexanal and 2-octenal, mainly) were found during accelerated storage of rapeseed oil (16 days at 60 \({}^{\circ}\)C) [51]. Additionally, in accelerated storage, [PERSON] et al. found that secondary oxidation products accounted for approximately 60% of total volatile compounds [21]. In our work, total aldehydes showed the highest increase during storage at 60 \({}^{\circ}\)C and especially as a consequence of cooking at 180 \({}^{\circ}\)C, reaching in this case, values of around 80% of the total area in the case of rapeseed and 90% for grape seed. Consequently, ketones and furans were more abundant in stored samples than in those submitted to cooking. The most abundant volatiles found in cooked rapeseed samples were 2,4-Heptadienal, (E,E) 2,4-heptadienal, nonanal, (E,E) 2,4-decadienal. 2,4-hepadienal has been described as a typical linolenic acid oxidation product, and it was reported as highly abundant in rapeseed oil treated at 160 \({}^{\circ}\)C for more than 30 min [52]. However, in the case of grape seed oil, the two decadienal isomers (2,4-decadienal and (E,E)-2,4-decadienal) were by far the most abundant compounds. These two odor-active compounds are associated with fried fat aroma [53] and oil incartidicity [54]. They form chromophores that absorb at 390 nm in the TBARs reaction, and not at 532 nm [47], so this method underestimates oxidation detection in those oils that give rise to these compounds. Regarding nonanal, it is related to the decomposition of hydroperoxides formed by the autoxidation of oleic acid [55] and reached the highest value in cooked samples of the highest monounsaturated oil (rapeseed oil). [PERSON] et al. analyzing volatile compounds in refined and cold press rapeseed oils during 10 days of storage at 60 \({}^{\circ}\)C found a significant increase in volatiles, especially of aldehydes, that were higher in the case of refined samples [22]. They also found that in refined oils, 2-hexenal was the most abundant compound with higher increases than the rest of the aldehydes and that 2-heptenal was correlated with the worst samples of refined rapeseed oil stored during 10 days. Terpenes are usually present in fresh oils. Their amounts in unheated oil were lower in rape seed oil than in coconut and grape seed oils. In all cases, they significantly decreased during the storage, but mostly with cooking (even disappearing in the case of rapeseed oil). These results agree with other papers in which this family of compounds was analyzed during different treatments of oils.