# Olive Oil with Ozone-Modified Properties and Its Application
## 2 Results and Discussion  
### Changes in the Chemical Composition of Olive Oil after Ozonation  
Two batches of ozonated olive oil were prepared with the final ozone concentration 0.04 mole O\({}_{3}\)/100 g oil and 0.10 mole O\({}_{3}\)/100 g oil, corresponding to 2 g and 5 g of ozone in 100 g olive oil, respectively. To assess the chemical composition of the refined oil (oil before ozonation) and after ozonation, the analysis of fatty acid profile after esterification was performed. The refined olive oil was of a similar composition to the olive oils reported in the literature [8, 9, 10]. Differences in the composition of the oil before and after ozonation result from the mechanism of the process itself. Before the reaction, the main components of the oil were fatty acids, while after the passage of ozone, new compounds are formed, including those with shorter carbon chains. The transitions were realized by the disruption of fatty acid molecules at the site of double bonds, the attachment of oxygen atoms, the breakdown of these unstable intermediates, and the formation of oxygen derivatives of organic compounds with different properties. Reactions in the system involved both ozone and radicals. The data presented in Table 1 demonstrate the changes in the composition of the oil depending on the ozone concentration. The levels of hexadecanoic acid, (92)-hexadec-9-enoic acid, and octadecanoic acid were stable even after the introduction of 0.10 mole O\({}_{3}\)/ 100 g oil. Significant decreases in the content of the oleic acid and linoleic acid were observed in the oil after ozonation (in comparison to refined olive oil) (\(p\) = 0.0273 and \(p\) = 0.0273 respectively; Kruskal-Wallis test). Eight compounds were formed after 0.10 mole of ozone and five compounds after 0.04 mole of ozone treatment. Significant increases were observed in five compounds' concentrations: nonanal, nonanoic acid, 9-oxonone acid, hexanal, and nonanediolic acid (\(p\) = 0.0241, \(p\) = 0.0241, \(p\) = 0.0241, \(p\) = 0.0241, respectively; Kruskal-Wallis test). Three compounds formed only in ozonated olive oil with 0.10 mole O\({}_{3}\)/100 g shown up in statistically insignificant amounts (\(p\) > 0.05; Kruskal-Wallis test). A decrease in the amount of oleic acid in the olive after ozonation and a concomitant increase in the contents of nonanal and nonanoic acid results from the reaction of ozone with the double bond in the fatty acid. Oxonone acid is the result of the action of an oxygen radical on the oleic acid molecule, and its amount increases with the concentration of ozone in the system (Figures 1 and 2). The loss of unsaturated acid, expressed as (92)-octadec-9-enoic acid, was 12.3% and 29.1% at the 0.04 mole O\({}_{3}\) and 0.10 mole O\({}_{3}\)/100 g, respectively. The low humidity of the olive oil results from the technological process conditions. The ozonated olive oil was characterised by an interesting, quite strong odour. The compounds responsible for the oil's flavour after the ozonation were identified by HS-SPME analysis (Figure 3). Interestingly, volatile compounds have not been detected in the headspace of olive oil. The odour of ozonated oils was mainly determined by aldehydes such as nonanal and hexanal (Table 2). In olive after ozonation with 0.10 mole O\({}_{3}\)/100 g oil, a statistically significant increase in the content of non-4-enal, nonanal, and hexanal were observed in comparison to the untreated oil (all \(p\) = 0.0241, \(p\) = 0.0429, \(p\) = 0.0429 respectively; Kruskal-Wallis test). An intensive aroma of the oil treated by the ozone with the higher concentration resulted in the higher content of nonanal (Figures 2 and 3). Nonanal, at its highest level in the headspace, has a very strong, diffusive, fat-floral, waxy fragrance. At the appropriate dilution, the greasy notes become more pleasant, floral-waxy, more pink and sweet, fresh as neroli [12]. Hexanal, an aldehyde affecting the final aroma of the olives, has a very strong, penetrating, greasy, green, and grassy scent.