## 3 Results and Discussion
### Oxidative Stability and Antioxidant Capacity  
The oxidative stability of VOO refers to its resistance to oxidative degradation. A key parameter used to characterize this resistance is the oxidative stability index (OSI), defined as the induction period (IP)--the time required for a significant increase in the oxidation rate under accelerated conditions [95; 96]. The results of the analysis of the VOOs produced with the Abencor laboratory system are shown in Table 4.  
Antioxidant capacity is defined as the total amount of oxidants neutralized by antioxidant mechanisms, representing the cumulative antioxidant activity present in VOO [97]. Phenolic compounds are among the most potent antioxidants in VOO which act as chain-breaking antioxidants. These compounds react with lipid radicals to form stable, non-reactive radicals, thereby interrupting the propagation phase of lipid peroxidation. In VOO, phenolic compounds exhibit their antioxidant activity primarily by scavenging peroxyl and alkyl radicals, as well as by chelating trace amounts of transition metal ions that may catalyze oxidative reactions [98; 99]. Tocopherols, another important class of antioxidants present in VOO, also scavenge peroxyl radicals. In addition, they are among the most effective natural quenchers of singlet oxygen, converting it to its ground state and thereby inhibiting singlet oxygen-mediated oxidation of unsaturated fatty acids [95]. The evaluation of the antioxidant capacity of EVOO reflects not only the contributions of phenolic compounds and tocopherols, but also of other minor antioxidants, which together enhance the nutritional value and oxidative stability of the oil through synergistic interactions. In this study, the antioxidant capacity of VOO obtained from olive paste subjected to FTT was assessed using the stable free radical DPPH. The results are presented in Table 4 as the percentage reduction of the DPPH radical. Given the differences in phenolic content,tocopherol composition, and fatty acid profiles among the studied olive varieties, it was anticipated that each would exhibit a distinct response to FTT in terms of oxidative stability and antioxidant capacity [3]. The Istarska Bjelica variety demonstrated strong tolerance to FTT, as evidenced by an increase in IP during both the cooling and heating phases, although a statistically significant increase in IP compared to the control was observed only after heating to 40 \({}^{\circ}\)C. This stability can be attributed to its robust antioxidant capacity, which remained unaffected by thermal treatment. Notably, Istarska Bjelica possesses the highest concentration of phenolic compounds among the tested varieties (Table 2), particularly oleocanthal, oleurropein algy-cone, and hydroxytyrosol--compounds recognized for their potent antioxidant activity [3]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **IP (min) \({}^{*}\)** & **AC (\% DPPH’ Reduction) \({}^{*}\)** \\ \hline Istarska Bjelica & \(p\leq\) 0.01 & \(p\) = 0.379 \\ \hline Control & 189 \(\pm\) 8 b & 60.07 \(\pm\) 0.25 \\  
\\ \hline \hline \end{tabular} \({}^{*}\)Variety had a significant effect (\(p\leq\) 0.05): presented \(p\)-values indicate the effect of temperature within each variety. Where significant (\(p\leq\) 0.05), [PERSON]’s multiple comparison test was conducted and different letters within column subsections indicate significant differences. All values are mean \(\pm\) standard deviation of three consecutive production batches.  
\end{table} 
Table 4: Induction period (IP) and antioxidant capacity (AC) of controls and oils produced with flash thermal treatment. In the Levantinka variety, a downward trend in IP was observed although not statistically significant. Antioxidant capacity also did not differ significantly from the control, except at 25 \({}^{\circ}\)C. The most pronounced decline in oxidative stability, especially under heating conditions, was observed in oils derived from the Oblica variety.