## 3 Results and Discussion
### Basic Quality Parameters and Processing Yield  
Thermal treatment of the olive paste prior to malaxation did not compromise the basic quality of any VOO produced at laboratory scale Abencor system. All oils remained within the \"extra virgin olive oil\" category (Table 1), as defined by current EU standards [51]. The acidity was significantly influenced by the health status of the olive fruit of Istarska Bjelica (\(p\leq 0.01\)) and Oblica (\(p\leq 0.001\)). However, the values of the free fatty acids were within a very narrow range of only 0.04 percentage units in Istarska Bjelica and 0.06 percentage units in Oblica, with few treatments being significantly different compared to the control. Other researchers investigating the effects of FTT on the quality of VOO have found no increase in acidity [27; 30; 52]. All thermal treatments prior to malaxation led to a statistically significant increase (between 47% and 81%) in the peroxide value (PV) compared to the untreated control. Acceleration of the oxidation process in our trial is most likely a consequence of the discontinuous phase of the FTT under the laboratory conditions used in this work. Despite  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**Acidity**} & \multirow{2}{*}{**PV**} & \multicolumn{2}{c}{**K Values**} & \multirow{2}{*}{**Yield (\%) \({}^{*}\)**} \\  & & **Acid \({}^{*}\)** & & & & \\ \hline Istarska & & & & & & \\ Bjelica & \(p\leq 0.01\) & \(p\leq 0.001\) & \(p\leq 0.05\) & \(p=0.522\) & \(p\leq 0.001\) & \(p\leq 0.05\) \\ \hline Control & 0.42 \(\  
this rise, PV levels in all samples remained well below the regulatory limit of 20 meq \(\text{Q}_{2}\)/kg, as stipulated by EU Regulations [51]. Similar results were reported by [PERSON] et al. [52] for VOO produced with FTT in industrial facilities, while [PERSON] et al. [27], who produced VOO with FTT on a laboratory scale, together with others who used industrial facilities, did not achieve any PV increase [24; 28; 29]. However, the specific extinction coefficients at 232 nm (\(\text{K}_{232}\)), which similarly to PV serves as indicator of the primary oxidation products in virgin oils, did not exhibit a significant increase across treatments. The reason may be that \(\text{K}_{232}\) includes only primary oxidation products formed from polyunsaturated fatty acids by photooxidation, while the peroxide number also includes those formed from oleic acid, which predominates in olive oil. The moderate oxidative deterioration of the oil under the applied conditions is also reflected by the fact that there was no statistically significant increase in \(\text{K}_{268}\) (except in Levantinka at 25 \({}^{\circ}\)C), which is associated with the presence of secondary oxidation products in virgin oils. Nevertheless, due to the potentially pro-oxidative effects of elevated temperatures as well as the influence of the discontinuous FTT process as a pretreatment for malaxation under laboratory conditions, additional indicators of oxidative stability were included in the study, which are discussed later in this document. One of the biggest challenges in conventional VOO production is the relatively low oil yield: 10-20% of the oil remains trapped in the cell-matrix or in the colloidal system of the olive paste and part is bound in an emulsion with the vegetable water [53]. Recent research has focused on improving extraction efficiency through the use of innovative technologies, often in combination with malaxation. Notably, the use of pulsed electric fields (PEF) has shown promising results [54; 55; 56; 57], as have and high hydrostatic pressure and ultrasound treatments [57; 58]. Moreover, combining several of these innovative techniques has demonstrated additional potential to enhance olive oil extraction and quality [59]. In contrast, thermal treatment of olive paste, either applied alone or in combination with malaxation, has not consistently improved oil yield [24; 25; 28; 60]. Our results are similar.