In this master's thesis, we focused on the development and manufacture of a portable measuring device for capturing transmission and fluorescence in near-ultraviolet and visible regions of the light spectrum. During the development and manufacture of the measuring device, special emphasis was placed on the repeatability of measurements. We compared the repeatability of the developed device to the repeatability of a professional laboratory setup, and found that our prototype measuring device achieves higher repeatability. Next, we tested the measuring device on different samples of vegetable oils, extra virgin olive oil (EVOO), refined olive oil (ROO) and refined sunflower oil (RSO). Based on the repeatability and measurement analysis of the vegetable oils, we discovered the advantages and the disadvantages of the developed device, and suggested possible upgrades.
As a part of the master's thesis, we performed various experiments with vegetable oils, in which oils were thermally processed or irradiated with light in controlled environments. The analysis of transmission and fluorescence measurements of heat-treated oils showed that the chemical composition of the ROO changes at lower temperatures (< 160 °C, time < 20 min) than the chemical composition of the EVOO (< 180 °C, time < 20 min). By irradiating the EVOO with visible and ultraviolet light, we found that the change in chemical composition is caused exclusively by ultraviolet light. Irradiation with sunlight had a particularly pronounced effect on change in the composition of the EVOO. We proved that for a shorter period of time than 30 hours, the original glass packaging offers good protection from ultraviolet light for the EVOO. Finally, we studied the mixtures of the EVOO and RSO. The mesurement analysis of of oil mixtures showed that the measuring device can detect a few percent of RSO mixed in the EVOO.
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