## 3 Results and Discussion
### Volatile Compounds  
Volatile compounds, both major and minor, play a critical role in determining the sensory quality and consumer perception of virgin olive oils (VOOs). Their composition is influenced by a multitude of factors, including olive cultivar, geographical origin, fruit ripeness, and technological parameters--particularly malaxation time and temperature. In accordance with the classification proposed by [PERSON] et al. [5], the volatile compounds identified in this study were grouped into three primary categories based on their biochemical, oxidative, or microbiological origins. Furthermore, compounds were classified into three levels of identification reliability, following the criteria established by [PERSON] et al. [61]. Tables S3 and S4 (Supplementary Material) contain the results of the analysis of volatiles in samples of VOO prepared on a laboratory scale in Abencor using a discontinuous FTT process as a pretreatment for malaxation. Table S5 presents the concentrations of volatile compounds generated via the lipoxygenase (LOX) pathway, which are largely responsible for the green and fruity sensory notes characteristic of high quality VOOs. In the control samples, clear varietal differences in the volatile profiles were observed. These findings align with previous studies on Croatian VOOs also produced at laboratory scale [35; 62; 63]. In comparison to control, flash thermal treatment significantly affected the sum of LOX-derived volatiles only in the Istarska Bjelica variety, where the concentration of total LOX volatiles achieved at 20 \({}^{\circ}\)C and 35 \({}^{\circ}\)C was significantly lower compared to control sample. Since statistical significance  
was not confirmed for the extreme temperature points (pretreatment of Istarska Bjelica at 15 \({}^{\circ}\)C and 40 \({}^{\circ}\)C), it can be assumed that disadvantages of laboratory-scale process (such as the exposure of the olive paste to oxygen and the additional time required to reach the malaxation temperature) could be the cause of such inconsistencies. Regardless, the results still highlight the complex, genotype-dependent response of the LOX pathway to thermal pretreatment, as also reported by other authors [10; 30; 64; 65; 66]. Beyond the LOX pathway, volatile compounds in VOOs can also arise from autoxidation and/or photooxidation processes. In the present study, three oxidation-derived volatile compounds were identified (Table S4 in the Supplementary Material). While the accumulation of nonanal was relatively uniform in all three varieties, a decrease in 2,4-hexadienal was observed in Istarska Bjelica compared to the other two varieties. This lower level reflects the higher oxidation resistance of Istarska Bjelica, as indicated by the induction time (Chapter 3.6). A statistically significant decrease in 2,4-hexadienal and consequently in the sum of volatile oxidation products was observed in the VOO of Oblica when pretreated at 40 \({}^{\circ}\)C.  
In addition to oxidative processes, microbiological activity during post-harvest olive storage can substantially contribute to volatile formation. The native microbiota present on olive fruit surfaces, including bacteria, yeasts, and molds, can proliferate during storage and metabolize fruit constituents, thereby producing various fermentation-related volatiles [5]. In this study, two microbial metabolites, 3-methylbutanal and 2-methylbutanal, were identified and quantified. Statistically significantly higher concentrations compared to control oils were observed at a pretreatment temperature of 25 \({}^{\circ}\)C in oils derived from Istarska Bjelica and Oblica, while Levantinka showed no significant changes at all. Given the short duration of the treatment, the lack of similarity between varieties, and the lack of a clear trend depending on the pretreatment temperature, the observed changes could not be associated with microbial activity during sample preparation.