Mia Ivanov

This study investigated, for the first time, the effects of pulsed electric field (PEF) pretreatment—applied prior to malaxation at 2–7 kV/cm for 30–90—on oil yield, quality parameters, and volatile profiles of virgin olive oils (VOO) from four representative Croatian autochthonous varieties: Istarska Bjelica and Rosulja (Istria), and Levantinka and Oblica (Dalmatia). Mild PEF conditions significantly increased oil yield (2.5–36%), with the strongest effects observed in varieties with low baseline yields. Basic quality parameters were largely unaffected, but volatile organic compound (VOC) profiles were markedly altered. PEF increased VOCs from the lipoxygenase (LOX) pathway, particularly at lower field strengths, and altered their composition, suggesting changes in the activity of the enzymes involved in their biosynthesis. Among these enzymes, LOX was analyzed, and its activity responded to PEF treatment in a cultivar-dependent manner. Furthermore, PEF generally reduced minor VOCs associated with oxidation and microbial activity. These findings demonstrate the potential of PEF as a non-thermal, sustainable technology for improving oil extraction efficiency while simultaneously enhancing the aroma profile of VOOs.

This study investigated, for the first time, the effects of pulsed electric field (PEF) pretreatment—applied prior to malaxation at 2–7 kV/cm for 30–90 —on oil yield, quality parameters, and volatile profiles of virgin olive oils (VOO) from four representative Croatian autochthonous varieties: Istarska Bjelica and Rosulja (Istria), and Levantinka and Oblica (Dalmatia). Mild PEF conditions significantly increased oil yield (2.5–36 %), with the strongest effects observed in varieties with low baseline yields. Basic quality parameters were largely unaffected, but volatile organic compound (VOC) profiles were markedly altered. PEF increased VOCs from the lipoxygenase (LOX) pathway, particularly at lower field strengths, and altered their composition, suggesting changes in the activity of the enzymes involved in their biosynthesis. Among these enzymes, LOX was analyzed, and its activity responded to PEF treatment in a cultivar-dependent manner. Furthermore, PEF generally reduced minor VOCs associated with oxidation and microbial activity. These findings demonstrate the potential of PEF as a non-thermal, sustainable technology for improving oil extraction efficiency while simultaneously enhancing the aroma profile of VOOs.

This study investigated the effects of ultrasonic treatment of olive paste prior to malaxation on oil yield (Y), enzyme activity and virgin olive oil (VOO) quality in four Croatian olive varieties: Istarska Bjelica, Rosulja, Oblica and Levantinka. The oils were extracted using the Abencor system according to a central composite experiment design, with treatment durations of 3–17 min and power levels of 256–640 W. The parameters analyzed included Y, oxidative stability index (OSI), antioxidant capacity (AC), phenolic and α-tocopherol content, volatile compounds, fatty acid profile, and the activity of lipoxygenase, β-glucosidase, polyphenol oxidase, and peroxidase. Olive variety was the most influential factor in all variables. The response surface methodology showed that ultrasonic treatment at low-to-medium intensity improved several quality attributes. For example, Y increased by 4% in Oblica, phenolic content increased by up to 17% in Istarska Bjelica, and OSI and AC increased by 13–15% in Istarska Bjelica and Levantinka. In contrast, longer treatment and higher ultrasound power had a negative effect. No significant differences were found in other parameters examined. Overall, the application of ultrasound led to measurable, though moderate, improvements in Y and VOO quality, with results strongly dependent on olive variety and treatment conditions. These results underline the need for further optimization tailored to each variety.

This study examined the effects of ultrasound (US) treatment of olive paste before malaxation on oil yield (Y), enzyme activity and virgin olive oil (VOO) quality in four Croatian olive varieties: Istarska Bjelica, Rosulja, Oblica and Levantinka. Oils were extracted using the Abencor system following a central composite design, with treatment times of 3–17 minutes and power levels of 256–640 W. Parameters analyzed included Y, oxidative stability (OSI), antioxidant capacity (AC), phenolic and α-tocopherol content, volatiles, fatty acid profile and the activity of lipoxygenase, β-glucosidase, polyphenol oxidase and peroxidase. Olive variety had the most significant influence across variables. Response surface methodology revealed that US treatment at low to moderate intensity improved certain quality traits. For example, Y increased by 4% in Oblica, phenolic content rose by up to 17% in Istarska Bjelica, and OSI and AC were enhanced up to 13–14% in Istarska Bjelica and Levantinka. However, prolonged exposure and high US power had adverse effects. Other investigated parameters showed no significant changes. The application of US resulted in measurable, although moderate, improvements in Y and VOO quality, with outcomes strongly influenced by olive variety and treatment conditions. These findings highlight the importance of further optimization tailored to each specific variety. In addition, a feasibility study is warranted to evaluate the practical implementation of US technology in VOO production, considering the relatively limited benefits observed.

The aim of this study was to determine the optimal parameters of pulsed electric field treatment to increase the activity of β-glucosidase and lipoxygenase, crucial enzymes that improve the nutritional quality and sensory properties of virgin olive oils. The activity of the enzymes was determined spectrophotometrically immediately after treatment of model systems (commercial enzymes and their substrates) with pulsed electric fields and after simulation of the malaxation process for 30 min at 25 °C. Pulsed electric field treatments were performed with electric field strengths of 2.67 and 13.33 kV/cm at frequencies of 25 and 125 Hz for 1, 2, and 5 min. The results showed a positive correlation of β-glucosidase activity with the electric field strength and time, with the first of the two factors having the greatest influence. Lipoxygenase activity was affected only by the duration of treatment: positively immediately after treatment and negatively after simulation of the malaxation process. Based on these results, pretreatment with a moderate pulsed electric field for 2 min before the malaxation process could be proposed to increase the activity of β-glucosidase and lipoxygenase, e.g., for the production of virgin olive oils with higher concentrations of polyphenols and desirable volatile compounds.

The aim of this study was to investigate the influence of thermal treatment and ultrasound on the activity of β-glucosidase and lipoxygenase, enzymes that determine the phenolic composition and sensory profile of virgin olive oil. Enzyme activity was determined spectrophotometrically in model systems consisting of commercial enzymes and their substrates. Thermal treatment was performed by tempering the enzymes and substrates at temperatures between 15 and 40 °C. Enzyme activity was measured 1 min after reaction and again after the additional incubation of the reaction mixture at 25 °C for 30 min to simulate the behavior of the enzymes during the malaxation process. Ultrasonic treatment of the model solutions was performed at 128, 320, and 640 W of the ultrasonic bath power for 1, 5, and 12 min. Enzyme activity was determined immediately after treatment and again after incubation at 25 °C for 30 min. The higher temperatures during thermal treatment increased the activity of both enzymes. During ultrasound treatment, the activity of both enzymes was positively affected by its duration. The higher power of ultrasound was a better choice for β-glucosidase and the lower one for lipoxygenase. The stimulation of enzyme activity by the studied techniques resulted in an acceleration of enzymatic reactions during the additional incubation, suggesting that the malaxation process could be shortened in virgin olive oil production.

High voltage electrical discharge plasma technology (HVED) is considered as a promising technology for wastewater remediation due to its fast removal rate and environmental compatibility. Olive mill wastewater (OMWW) treatment presents crucial environmental issues because of its high organic load and intense toxicity and phytotoxicity. The effect of cold plasma at frequencies of 60 Hz and 120 Hz, with injected gas (air, oxygen and nitrogen) and with and without the addition of FeCl₃x6H₂O, during 30 min, on degradation and removal of organic compounds, as well as polyphenols from OMWW, were investigated. The efficiency of cold plasma was monitored by pH, temperature, electroconductivity, redox potential, oxygen saturation and reduction of chemical oxygen demand (COD) and polyphenols. The best removal efficiency of 50.98% of organic compounds was achieved at 120 Hz with nitrogen and the addition of FeCl₃x6H₂O, and a 60.32% reduction of polyphenols at a frequency of 60 Hz with the air and FeCl₃x6H₂O added was obtained. Also, the plasma treatment resulted in a decrease in coloring intensity, with the most significant color change at 120 Hz with the addition of FeCl₃x6H₂O with nitrogen and air.

In this study, we designed high fiber cookie recipe without using additives by means of extrusion-based 3D printing. We aimed to relate printing quality and cookie physical properties with dough rheology and dietary fiber content depending on the flour (oat, rye, rice, and carob flour) and fat type (olive oil or butter). The flour choice influenced all cookie quality parameters: baking loss, color, line height and width, and dietary fiber content. Results indicated that lower baking loss and better printing quality were obtained for cookie dough containing olive oil, which had higher viscosity and consistency coefficient compared with dough containing butter. Cookies with olive oil in which part of the oat flour was replaced with rye and carob flour were printed with high accuracy (≥98%), close to the ideal 3D shape. Overall, this study demonstrates the importance of selecting fat and particularly flour, as well as the extrusion rate on the quality and repeatability of 3D-printed cookies.