Effects of Dietary Fat Oxidation Products and Flavonols on Lipoprotein Oxidation

Various studies suggest that oxidative modifications of low density lipoprotein (LDL), and also other lipoproteins, have an important role in the development of atherosclerosis. In addition to the oxidation products formed endogenously, oxidised triacylglycerols (TAG) and oxysterols in the diet contribute to the oxidised lipoproteins found in circulation. However, studies on both the effect of oxidised dietary lipids on lipoprotein lipid oxidation and the reactions that modify oxidised fat after ingestion have been scarce. Studies on the effects of dietary antioxidants on the lipid oxidation in vivo and the risk of atherosclerosis have been inconclusive. More clinical trials are needed to test the importance of lipoprotein oxidation as a cardiovascular risk factor in humans. In the recent years, various methods have been optimised and applied to the analysis of lipid oxidation products in vivo, and information on the molecular structures of oxidised lipids in plasma, lipoproteins and atherosclerotic plaques has started to accumulate. However, specific structures of oxidised TAG molecules present in these tissues and lipoprotein fractions have not been investigated earlier. In the orginal research in this thesis, an approach based on highperformance liquid chromatographyelectrospray ionisationmass spectrometry (HPLCESIMS) and baseline diene conjugation (BDC) methods was used in order to investigate lipid oxidation level and oxidised TAG molecular structures in pig and human lipoproteins after dietary interventions. The approach was optimised with human LDL samples, which contained various oxidation products of TAG. LDL particles of hyperlipidaemic subjects contained an elevated amount of conjugated dienes. In the pig studies, several oxidised TAG structures with hydroxy, keto, epoxy or aldehydic groups were found in chylomicrons and VLDL after diets rich in sunflower seed oil. Also, the results showed that oxidised sunflower seed oil increased the oxidation of lipoprotein lipids and their TAG molecules. TAG hydroperoxides could be detected neither in the small intestinal mucosa of the pigs fed on the oxidised oil nor in their chylomicrons or VLDL.6 In the clinical studies, dietary flavonol aglycones extracted from sea buckthorn berries did not have an effect on lipoprotein lipid oxidation and other potential risk factors of atherosclerosis, but their absorption was demonstrated. Oil supplementation seemed to increase the bioavailability of the flavonols. Oxidised TAG molecules were detected in LDL particles of the subjects after both flavonol and control diets.

Use of the Optical Cantilever Microphone in Photoacoustic Spectroscopy

A novel cantilever pressure sensor was developed in the Department of Physics at the University of Turku in order to solve the sensitivity problems which are encountered when condenser microphones are used in photoacoustic spectroscopy. The cantilever pressure sensor, combined with a laser interferometer for the measurement of the cantilever movements, proved to be highly sensitive. The original aim of this work was to integrate the sensor in a photoacoustic gas detector working in a differential measurement scheme. The integration was made successfully into three prototypes. In addition, the cantilever was also integrated in the photoacoustic FTIR measurement schemes of gas-, liquid-, and solid-phase samples. A theoretical model for the signal generation in each measurement scheme was created and the optimal celldesign discussed. The sensitivity and selectivity of the differential method were evaluated when a blackbody radiator and a mechanical chopper were used with CO₂, CH4, CO, and C2H4 gases. The detection limits were in the sub-ppm level for all four gases with only a 1.3 second integration time and the cross interference was well below one percent for all gas combinations other than those between hydrocarbons. Sensitivity with other infrared sources was compared using ethylene as an example gas. In the comparison of sensitivity with different infrared sources the electrically modulated blackbody radiator gave a 35 times higher and the CO2-laser a 100 times lower detection limit than the blackbody radiator with a mechanical chopper. As a conclusion, the differential system is well suited to rapid single gas measurements. Gas-phase photoacoustic FTIR spectroscopy gives the best performance, when several components have to be analyzed simultaneously from multicomponent samples. Multicomponent measurements were demonstrated with a sample that contained different concentrations of CO₂, H₂O, CO, and four different hydrocarbons. It required an approximately 10 times longer measurement time to achieve the same detection limit for a single gas as with the differential system. The properties of the photoacoustic FTIR spectroscopy were also compared to conventional transmission FTIR spectroscopy by simulations. Solid- and liquid-phase photoacoustic FTIR spectroscopy has several advantages compared to other techniques and therefore it also has a great variety of applications. A comparison of the signal-to-noise ratio between photoacoustic cells with a cantilever microphone and a condenser microphone was done with standard carbon black, polyethene, and sunflower oil samples. The cell with the cantilever microphone proved to have a 5-10 times higher signal-to-noise ratio than the reference detector, depending on the sample. Cantilever enhanced photoacoustics will be an effective tool for gas detection and analysis of solid- and liquid-phase samples. The preliminary prototypes gave good results in all three measurement schemes that were studied. According to simulations, there are possibilities for further enhancement of the sensitivity, as well as other properties, of each system.

The Combined treatment of UV Light and Titanium Dioxide (TiO2) in Grease Filtration Technique

The aim of this thesis was to identify the best grease removal technique with the application of low power of UV light to TiO2 coated grease filters. The treatment with various power series of ozone generating and ozone free lamps to normal grease filters and TiO2 coated grease filters were examined and the obtained results are compared to each other in this paper. The effect of ozone reaction was observed and compared with the effect of TiO2. The experiments were solely based on the photo oxidation and photo catalytic oxidation reactions. TiO2 is a green catalyst used in the photocatalytic reaction. Sunflower oil was used for grease production and tetracholoroethylene as a solvent. Grease samples were collected from the ventilation duct connected to the cooking hood system. Sample extraction was done in ultrasonic bath with the principle of sonication. The sample analysis was done by FTIR machine. The result determining the concentration of grease was the quantification of saturated C-H bonds in the chosen peak group of the spectrum. A very low power of UVC light functions perfectly with the Titanium dioxide. The experimental results have shown the combined treatment of titanium dioxide and UV light is an effective method in grease removal process. The photocatalytic reaction with titanium dioxide is better than photo oxidation reaction with ozone treatment. Photocatalytic reaction is environmentally friendly, energy efficient and economical.